Special thanks to Dr. Benedikt Steuten for critical reading of the manuscript. The original work on the chitinases was carried out by Dr. Thorsten Langner. The laboratory of VG is supported by the Cluster of Excellence in Plant Sciences (CEPLAS, DFG EXC 1028) and BioSC, the laboratory of KS is supported by BioSC. KB is supported by BioSC. The scientific activities of the Bioeconomy Science Center (BioSC) were financially supported by the Ministry of Innovation, Science and Research within the framework of the NRW Strategieprojekt BioSC (No. 313/323-400-00213). LF is supported by a doctoral fellowship of the DFG International Research Training Group 1525 iGRADplant.

1. Generation of Deletion Constructs
<ol>
	<li>Generate a plasmid containing the deletion construct (Figure 1) comprising a respective 1 kb upstream flank (UF) and downstream flank (DF) each and the appropriate resistance cassette flanked by blunt cutting restriction sites. 
	NOTE: Any cloning strategy can be used (for cloning see reference 22) we recommend Golden Gate cloning for such plasmids 9.</li>
	<li>Excise the deletion construct from the plasmid using a blunt cutter to obtain 1 &#181;g DNA of the deletion construct 9. Purify the deletion construct to eliminate enzyme and buffer 22 e.g. by using commercial reagents and follow the manufacturer&#39;s instructions. 
	NOTE: The vector backbone can remain in the transformation mixture.</li>
</ol>
2. Preparation of Protoplasts
NOTE: Keep sterile conditions during all times of the experiment. The cell wall is a strong protective barrier that limits access of molecules to the plasma membrane. To allow uptake of the DNA containing the deletion construct, the cell wall needs to be removed by cell wall degrading enzymes in a protoplasting reaction. Critical steps in protoplast preparation are 1) osmotic stabilization of the medium and 2) avoiding mechanical stress on the protoplasts.
<ol>
	<li>Mark 2 ml tubes with a round bottom to freeze the protoplasts and cool them down at -20 &#176;C. Start a pre-culture in 3 ml YEPS-Light from a fresh plate of the strain with the desired genetic background. Incubate on a rotating wheel for 24 hr at 28 &#176;C. 
	NOTE: The strain can be the solopathogenic strain SG200 10, wildtype strains, tester strains such as AB33 23, or any mutant background for generation of double mutants. Make sure the strain is free of the desired resistance.</li>
	<li>Dilute the culture in 50 ml YEPS-Light in a baffled flask and incubate on an orbital shaker at 28 &#176;C with 200 rpm. 
	NOTE: The doubling time is about 2 hr for wildtype strains. Allow three duplications minimum.</li>
	<li>Grow until exponential phase. Ensure that the optical density, measured at a wavelength of 600 nm (OD600), is around 0.8 (0.6 to 1.0 is acceptable). An OD600 of 1.0 corresponds to about 1 to 2 x 107U. maydis cells per ml.</li>
	<li>Check the cells for contamination under a microscope. Use 40x&#160;magnification. Pellet the cells of the complete 50 ml culture for 5 min, 1,500 x g and discard the supernatant. Resuspend the pellet in 25 ml sodium citrate, sorbitol solution (SCS), centrifuge 5 min, 1,500 x g, and discard supernatant. 
	NOTE: Bacterial contaminations can be identified as small and often moving cells. Fungal contaminations can be identified based on a different cell shape or size compared to the cigar shaped cells of U. maydis.</li>
	<li>During centrifugation prepare protoplasting solution (12.5 mg/ml Trichoderma lysing enzymes, in SCS; prepare 3 ml per cell pellet; filter sterilize through a 22 &#181;m filter; solution has to be fresh for optimal enzymatic activity). SCS is an osmotic stabilizer to prevent rupture of protoplast upon removal of the cell wall.</li>
	<li>Resuspend the pellet in 2 ml protoplasting solution. Incubate for 5 to 20 min at RT and check under the microscope until 30 to 40% of the cells are round or like pinheads (Figure 2). 
	NOTE: Perform all steps on ice from now on and handle protoplasts with care!</li>
	<li>Wash 3x in 10 ml cold (4 &#176;C) SCS, centrifuge at 1,000 x g for 5 min.</li>
	<li>Resuspend the pellet in 10 ml cold sorbitol, TrisHCl, CaCl2 solution (STC), spin at 1,000 x g for 5 min, discard supernatant. Resuspend the pellet in 1 ml cold STC, make 100 &#181;l aliquots in the cooled tubes. Freeze the aliquots at -80 &#176;C until further use.</li>
</ol>
3. Transformation of U. maydis
NOTE: The transformation of U. maydis protoplasts relies on the polyethylene glycol (PEG)-mediated transformation method, which is technically simple and opposed to electroporation or biolistic transformation does not require specialized equipment.
<ol>
	<li>Prepare the two-layered selection plates (2 plates per transformation reaction). The bottom layer contains the antibiotic in a doubled concentration. Pipet 12 ml of RegLight containing 400 &#181;g/ml hygromycin (or 300 &#181;g/ ml nourseothricin or 4 &#181;g/ml carboxin or 1 mg/ml G418) into a Petri dish. Avoid bubbles. 
	NOTE: Bottom layer plates may be stored a couple of days at 4 &#176;C, but prepare the top layer freshly during transformation (see below).</li>
	<li>Thaw protoplasts on ice (1 tube/transformation). Add 1 &#181;l heparin (15 mg/ml). Add 1 &#181;g DNA (linearized construct) or 10 &#181;l H2O (water control). Incubate for 10 min on ice.</li>
	<li>During this time, for the upper layer spread 12 ml liquefied RegLight (boil and cool to 60 &#176;C) onto the RegLight bottom plate. 
	NOTE: This layer does not contain antibiotics.</li>
	<li>Add 500 &#181;l STC/PEG (polyethylene glycol) to the transformation tube (3. 2) and mix carefully by inverting the tube. Incubate 15 min on ice.</li>
	<li>Distribute each transformation reaction on two of the two-layered RegLight plates. Spread carefully and slowly with a glass pipet. Incubate plates upright at 28 &#176;C for 5 to 7 days until transformants grow as colonies. Obtain about 100-200 colonies per plate. 
	NOTE: Lower numbers might be caused by &#34;bad&#34; protoplasts that either contain too much cell wall and therefore cannot take up DNA or cannot regenerate. The former can be tested by transformation with a self-replicating plasmid, the latter by testing regeneration on plates without antibiotics.</li>
	<li>Prepare YEPS-Light plates containing the appropriate antibiotic at 200 &#181;g/ml hygromycin (or 150 &#181;g/ ml nourseothricin or 2 &#181;g/ml carboxin or 500 &#181;g/ml G418; these concentrations equal half of the one used for bottom plates). Re-purify at least 24 putative transformant colonies on these plates. Single colonies should be obtained. At the same time streak out the original strain on non-selective media. 
	NOTE: Plates can be stored at 4 &#176;C for 1-2 weeks.</li>
</ol>
4. Verification of Correct Deletion Events
NOTE: The mutations are verified in a three-step procedure (Figure 1). First, candidates that contain the wildtype copy of the gene are excluded by PCR. Second, the integration of the resistance cassette into the locus is verified by PCR. Third, the integration of the resistance cassette only into the desired locus is verified by Southern blot analysis. Careful strain verification is essential, so that mutant phenotypes truly correlate with the deletion.
<ol>
	<li>First Diagnostic PCR 20
	<ol>
		<li>Design primers pairing in the gene to be deleted that result in a product of 250-600 bp (Figure 1). Such small products are easy to amplify in a colony PCR, and long enough for detection in standard gel electrophoresis.</li>
		<li>For each candidate and the original strain as a positive control, resuspend a little bit (amount of a pinhead) of cell material of a single colony with a toothpick in 20 &#181;l 0.02 M NaOH. Incubate at RT for 30 min. 
		NOTE: Use fresh colonies. If the plates are older than 1 week re-streak to obtain a fresh colony.</li>
		<li>Use 1 &#181;l of the cell suspension for the PCR immediately. Run a standard PCR reaction and analyze resulting fragments. 
		NOTE: These samples cannot be stored. 
		NOTE: This PCR tests for presence of the wildtype gene and thereby allows rapid identification of negative candidates in which the gene of interest has not been replaced. Clones yielding bands in this PCR reaction will be discarded. One such negative clone should anyway be carried along as an additional negative control. Candidates without a PCR product have to be analyzed further. For genes without detrimental effects approximately half of the candidates should contain the wildtype gene, while the other half should not result in a band. This would correspond to a homologous recombination rate of 50%.</li>
	</ol>
	</li>
	<li>Second Diagnostic PCR
	<ol>
		<li>Preparation of genomic DNA. 
		NOTE: Genomic DNA (gDNA) can be prepared using two different protocols. The first involves toxic reagents like phenol and chloroform and hence, should be handled only by experienced researchers (described in 4.2.1.1 to 4.2.1.5) while the second can also be handled by less experienced students (described in 4.2.1.6 to 4.2.1.11). Both protocols are working reliably. Step 4.2.1.1 is identical for both protocols.
		<ol>
			<li>Inoculate 5 ml YEPS-Light with each candidate and incubate on a rotating wheel for 24 hr at 28 &#176;C. Drop 2 &#181;l of the culture on a CM plate. Keep the culture sterile. 
			NOTE: Following is a standard protocol (CAUTION: toxic steps).</li>
			<li>Put 1 scoop (~200 &#181;l) of HCl-washed glass beads to 2 ml tubes. Add 2 ml of the U. maydis culture. Spin 12,000 x g for 5 min. Discard supernatant (pellet can be frozen at this stage). Add 500 &#181;l Phenol/Chloroform/Isoamylalcohol (25:24:1) to the pellet. CAUTION! PHENOL IS TOXIC!</li>
			<li>Add 500 &#181;l Usti-lysis-buffer 1. Shake for 6 to 10 min on a vibrax at 1,000 rpm. Verify that the cell pellet is completely resuspended, but avoid extended shaking to prevent shearing of the gDNA. Spin at 12,000 x g for 15 min. Transfer 400 &#181;l of the aqueous phase into the new reaction tube (do not touch the interphase).</li>
			<li>Add 1 ml 100 % (v/v) ethanol. Invert the tube 3x to mix, observe the cloud of DNA that shortly appears. Spin at 12,000 x g for 5 min. Remove supernatant and wash with 200 &#181;l 70% EtOH. Do not resuspend the pellet in this stage.</li>
			<li>Remove supernatant completely (do not let the pellet dry completely). Add 50 &#181;l TE/RNase. Dissolve gDNA by shaking at 400 rpm at 50&#176;C for 10 min. Analyze 2 &#181;l of the gDNA on a 0.8 % agarose gel 20. 
			NOTE: The steps below comprise an alternative non-toxic protocol.</li>
		</ol>
		</li>
		<li>Alternate preparation of genomic DNA
		<ol>
			<li>Put 1 scoop (~200 &#181;l) of HCl washed glass beads to 2 ml tubes. Add 2 ml of the U. maydis culture and spin at 12,000 x g for 5 min. Discard supernatant&#160;(pellets can be frozen at this stage).</li>
			<li>Add 500 &#181;l Usti Lysis buffer 2 to the pellet. Shake for 5 to 15 min on a vibrax at 1,000 rpm. Verify that the cell pellet is completely resuspended.</li>
			<li>Incubate the tubes at 65 &#176;C for 15 to 20 min. Using appropriate incubators designed to host 2 ml tubes is critical. Then, place it on ice for 5 min.</li>
			<li>Add 100 &#181;l 8 M potassium acetate, vortex or invert 8 to 10 times. Spin 12,000 x g for 15 min at RT.</li>
			<li>Transfer 500 &#181;l of the supernatant to a fresh 1.5 ml tube and add 400 &#181;l isopropanol. Vortex or invert 8 to 10 times. Spin 12,000 x g for 15 min. Remove supernatant and wash with 500 &#181;l 70% EtOH. Spin 12,000 x g for 5 min.</li>
			<li>Soak off supernatant completely! Eventually, add a short spin (10 sec) to remove residual liquid. Let the DNA pellet dry for 3 to 5 min. Add 50 &#181;l TE/RNAase and incubate at 50 &#176;C for 10 to 15 min at 400 rpm.</li>
		</ol>
		</li>
		<li>PCR
		<ol>
			<li>Design two primer pairs with one of them binding outside the flanks and the corresponding one binding within the resistance cassette (UF-f, RC-r; RC-f, DF-r, Figure 1) 9.</li>
			<li>Use 1 &#181;l of a 1:10 dilution of the gDNA of every candidate as a template in 2 PCR reactions verifying the correct insertion upstream and downstream 9.</li>
			<li>Use standard PCR reactions for each candidate and analyze resulting fragments 22. 
			NOTE: These PCRs test for the insertion of the resistance cassette in the correct genomic locus. If products are obtained for both sides, the candidate is likely a correct insertion. However, also candidates where only one side (upstream or downstream) could be confirmed should be carried along for further analysis in case that PCR reactions simply failed for one flank.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Verification of Correct Genomic Insertion by Southern Blot Analysis 22
	<ol>
		<li>Digest 15 &#181;l of gDNA (4.2.1) of the mutant candidates and the corresponding wildtype/progenitor strain with an appropriate enzyme that cuts outside the locus/construct and in addition, cuts either in the gene or in the resistance cassette leading to clearly distinguishable patterns (Figure 1) 8. 
		NOTE: None of the expected bands should be larger than 10 kb, so that they are clearly distinguishable from undigested DNA.</li>
		<li>Use the upstream and the downstream flank as probes. To label them for example use the PCR DIG labelling Kit or any similar standard method. Mix the labelled probes in a 1:1 molecular ratio and carry out the Southern blot. Keep at least two independent correct transformants. 
		NOTE: The wildtype pattern should be clearly detectable in the original strain and the correct clones should contain only the expected bands. Additional bands only present in the candidates indicate other insertions of the construct in a wrong locus. Such clones should be discarded. The negative candidate identified in the first diagnostic PCR should contain the wildtype bands and the bands (unpredictable in size) of the wrongly integrated deletion construct.</li>
	</ol>
	</li>
	<li>Glycerol Stocks 
	NOTE: Glycerol stocks serve to maintain the clones for years in strain collections. At least two independent transformants should be kept for each mutant. This allows comparing phenotypes that should be identical.
	<ol>
		<li>Grow 5 ml cultures of the confirmed mutant strains in YEPS-Light on a rotating wheel for 24 hr at 28 &#176;C Mix 500 &#181;l of each culture with 500 &#181;l NSY-Glycerol-medium. Invert tube until culture and medium are well mixed. Glycerol in the medium prevents the formation of ice crystals.</li>
		<li>Freeze at -80 &#176;C. Re-streak a part of the frozen culture to test if the stock is functional.</li>
	</ol>
	</li>
</ol>
5. Microscopic Phenotypes
<ol>
	<li>Grow 5 ml cultures of wildtype and mutant strains in YEPS-Light on a rotating wheel for 12 hr at 28 &#176;C.</li>
	<li>Next day, dilute the culture to an OD600 of about 0.1 and grow it till an OD600&#160; between 0.5 and 0.7. An OD600 of 1.0 corresponds to about 1 to 2 x 107 U. maydis cells per ml.</li>
	<li>Inspect the cell morphology microscopically. 
	NOTE: Healthy cells appear cigar shaped (Figure 4, WT). Pronounced vacuoles or filament formation indicate that the cells are stressed. 
	NOTE: Depending on the expected mutant phenotype, the analysis can be adapted, e.g., if reporter strains are used the appropriate assay can be carried out at this stage. If cell morphology is changed statistical analysis should be conducted, e.g., to determine the mean cell length.</li>
</ol>
6. Infection Assay
NOTE: The seedling infection assay has been visualized previously in this journal 11. It can either be carried out using a haploid, solopathogenic strain background such as SG200 10 or by mixing compatible mating partners which both carry the mutation.
<ol>
	<li>Grow at least 40 maize seedlings per strain for 7 days at a light cycle of 16 hr, 200 &#181;E, 28 &#176;C/22 &#176;C (day/night). They should be at the 3-leaf stage and 10-15 cm tall at the day of infection.</li>
	<li>Two days before infection, start a pre-culture of the strains in 5 ml YEPS-Light on a rotating wheel for 24 hr at 28 &#176;C. Grow a main culture in 50 ml YEPS-Light up to OD600 = 1.0 (cell division rate = 2 hr, allow 3 divisions minimum, can be done O/N).</li>
	<li>Spin down the cells of 50 ml culture at 1,500 x g for 5 min and discard the supernatant. Wash 3x with sterile H2O. Resuspend the cells in sterile H2O to an OD600 of 3.0. If necessary, mix the mating partners.</li>
	<li>Inject 250 - 500 &#181;l of the cell suspensions into the stem of 7 day old maize seedlings using a small syringe. Use sterile H2O as a control. Keep infected seedlings for an additional 7-14 days in the same light and temperature conditions. Score the phenotype of each plant according to healthy, chlorosis, anthocyanin formation, small tumors, large tumors, dead plants 10. 
	NOTE: Scoring can be done as early as 7 days and repeated at 14 days to follow infection over time.</li>
</ol>

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F., Maniatis, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Molecular Cloining: a laboratry manual. , (1989).</li><li>Brachmann, A., Weinzierl, G., K&#228;mper, J., Kahmann, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+genes+in+the+bW/bE+regulatory+cascade+in+Ustilago+maydis.">Identification of genes in the bW/bE regulatory cascade in Ustilago maydis.</a> Molecular Microbiology. 42, 1047-1063 (2001).</li><li>Becht, P., Vollmeister, E., Feldbr&#252;gge, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+for+RNA-binding+proteins+implicated+in+pathogenic+development+of+Ustilago+maydis.">Role for RNA-binding proteins implicated in pathogenic development of Ustilago maydis.</a> Eukaryotic Cell. 4, 121-133 (2005).</li><li>Vollmeister, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tandem+KH+domains+of+Khd4+recognize+AUACCC+and+are+essential+for+regulation+of+morphology+as+well+as+pathogenicity+in+Ustilago+maydis.">Tandem KH domains of Khd4 recognize AUACCC and are essential for regulation of morphology as well as pathogenicity in Ustilago maydis.</a> RNA. 15, 2206-2218 (2009).</li><li>Stock, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Applying+unconventional+secretion+of+the+endochitinase+Cts1+to+export+heterologous+proteins+in+Ustilago+maydis.">Applying unconventional secretion of the endochitinase Cts1 to export heterologous proteins in Ustilago maydis.</a> Journal of Biotechnology. 161, 80-91 (2012).</li><li>Baumann, S., Pohlmann, T., Jungbluth, M., Brachmann, A., Feldbr&#252;gge, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Kinesin-3+and+dynein+mediate+microtubule-dependent+co-transport+of+mRNPs+and+endosomes.">Kinesin-3 and dynein mediate microtubule-dependent co-transport of mRNPs and endosomes.</a> Journal of Cell Science. 125, 2740-2752 (2012).</li><li>Pohlmann, T., Baumann, S., Haag, C., Albrecht, M., Feldbr&#252;gge, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+FYVE+zinc+finger+domain+protein+specifically+links+mRNA+transport+to+endosome+trafficking.">A FYVE zinc finger domain protein specifically links mRNA transport to endosome trafficking.</a> eLife. 4, (2015).</li><li>Kronstad, J. W., Leong, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+of+two+Alleles+of+the+b-Locus+of+Ustilago.">Isolation of two Alleles of the b-Locus of Ustilago.</a> P Natl Acad Sci USA. 86, 978-982 (1989).</li><li>Koepke, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+RNA-binding+protein+Rrm4+is+essential+for+efficient+secretion+of+endochitinase+Cts1.">The RNA-binding protein Rrm4 is essential for efficient secretion of endochitinase Cts1.</a> Molecular &amp; cellular proteomics. 10, (2011).</li><li>Schuler, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hxt1,+a+monosaccharide+transporter+and+sensor+required+for+virulence+of+the+maize+pathogen+Ustilago+maydis.">Hxt1, a monosaccharide transporter and sensor required for virulence of the maize pathogen Ustilago maydis.</a> New Phytologist 206. , 1086-1100 (2015).</li><li>Schuster, M., Schweizer, G., Reissmann, S., Kahmann, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genome+editing+in+Ustilago+maydis+using+the+CRISPR-Cas+system.">Genome editing in Ustilago maydis using the CRISPR-Cas system.</a> Fungal Genetics and Biology. , (2015).</li></ol>

The authors have nothing to disclose.

This protocol describes how to generate deletion mutants for reverse genetic studies in U. maydis. The starting point is a deletion construct that contains flanking sequences of the gene-of-interest containing sequences of about 1 kb upstream of the start and downstream of the stop-codon as well as an appropriate resistance cassette as it was previously optimized 7,9. The constructs have to be individually generated for each gene and carefully verified for sequence errors prior to deleting the gene. P...

Ustilago maydis is a phytopathogenic model fungus that has been studied extensively for decades 1,2. It exists in two morphologies, a yeast-like, non-pathogenic stage and a filamentous, infectious form 3. Universal breakthrough discoveries such as homologous recombination and DNA repair mechanisms were made in the yeast-like growth stage of this fungus 4. Furthermore, the morphological switch to the infectious filament and virulence factors important for infection are well-characterized 5,6. The increasing molecular knowledge about biology and virulence of this smut fungus relies on a straightforward gene replacement strategy 7-9 supported by an excellent genome annotation 10 and the ease of reverse genetics using, e.g., the well-organized plasmid collection at our institute (http://www.mikrobiologie.hhu.de/ustilago-community.html). Standardized, rapid infection assays in maize seedlings allow detailed studies of pathogenicity factors 11.
The genome of U. maydis contains about 6,900 genes 10. To study their function, they can be deleted individually or in combination due to an efficient homologous recombination system. Flanking regions of about 1 kb containing perfectly homologous ends are ideal for rates of homologous recombination greater than 50%, but already 250 bp with non-homologous ends allow some degree of correct integration of the construct 9. Currently, five different resistance cassettes, hygR, cbxR, natR, G418R, and phleoR mediating resistance against hygromycin, carboxin, nourseothricin, G418 and phleomycin, are employed to select for transformants 7,9. In addition, the hygromycin resistance has been developed into a recyclable cassette (FRT-hygR) that can be removed by the transient expression of a heterologous&#160;FLP recombinase 12. This allows removal of the resistance cassette and thereby in theory unlimited genetic modifications. Phleomycin is mutagenic 13, so that with the new cassettes, in particular the recyclable hygR cassette, the use of phleoR is decreasing. Quadruple mutants can thus be generated using the other four cassettes, but for quintuple mutants, the FRT-hygR system is recommended 14.
This general gene deletion strategy has been successfully transferred to other smut fungi such as Sporisorium reilianum 15, U. hordei 16, or U. esculenta 17 and therefore offers the potential for further applications in yet genetically intractable organisms with an efficient homologous recombination system. Moreover, organisms lacking homologous recombination can be modified to improve genetic engineering as exemplified by the deletion of genes involved in non-homologous-end-joining in Neurospora crassa 18,19.
Here we describe the published gene deletion strategy for U. maydis 7,9 in experimental detail with a focus on the rapid and accurate verification of the candidates. As an example, we use the fungal chitinases and depict the generation of single mutants as well as multiple deletion strains 20,21. Chitinases are interesting examples, because they act on chitin in the rigid cell wall. Cell wall remodeling is required for morphological changes during cell division, switch to filamentous growth, and spore formation. Hence, in deletion mutants phenotypes throughout the lifecycle can be expected.

<table border="0" cellpadding="0" cellspacing="0" width="1138">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">Aminobenzoeic acid (Free Acid)</td>
			<td style="width:183px;">Sigma Aldrich</td>
			<td style="width:124px;">A-9878</td>
			<td style="width:485px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Bacto Agar&#160;</td>
			<td style="width:183px;">BD</td>
			<td style="width:124px;">214010</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Bacto Peptone</td>
			<td style="width:183px;">BD</td>
			<td style="width:124px;">211677</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Bacto Yeast Extract&#160;</td>
			<td style="width:183px;">BD</td>
			<td style="width:124px;">212750</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:347px;">CaCl2*2H2O</td>
			<td style="width:183px;">Gr&#252;ssing GmbH</td>
			<td style="width:124px;">10234</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">Ca-pantothenat (Hemi-Ca. salt)</td>
			<td style="width:183px;">Sigma Aldrich</td>
			<td style="width:124px;">P-2250</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Carboxin&#160;</td>
			<td style="width:183px;">Sigma Aldrich</td>
			<td style="width:124px;">45371</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Casamino acids&#160;</td>
			<td style="width:183px;">BD</td>
			<td style="width:124px;">223050</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">Cholinchlorid</td>
			<td style="width:183px;">Sigma Aldrich</td>
			<td>C-1879</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">Citric acid</td>
			<td style="width:183px;">ChemSolute</td>
			<td style="width:124px;">24,321,000</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:347px;">CuSO4*5H2O</td>
			<td style="width:183px;">Fluka</td>
			<td style="width:124px;">61240</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">D(+)Sucrose&#160;</td>
			<td style="width:183px;">Roth</td>
			<td style="width:124px;">4621.1</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">DNA degr. free acid&#160;</td>
			<td style="width:183px;">Sigma-Aldrich</td>
			<td style="width:124px;">D-3159</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">EDTA</td>
			<td style="width:183px;">Sigma Aldrich</td>
			<td style="width:124px;">E4378</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:347px;">FeCl3*6H2O</td>
			<td style="width:183px;">Gr&#252;ssing GmbH</td>
			<td style="width:124px;">10288</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">Geneticin (G418) disulfate salt</td>
			<td style="width:183px;">Sigma Aldrich</td>
			<td style="width:124px;">A1720</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Trichoderma lysing enzymes</td>
			<td>Sigma Aldrich</td>
			<td>L1412</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">Glucose</td>
			<td style="width:183px;">Caelo</td>
			<td style="width:124px;">2580</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">Glycerin&#160;</td>
			<td style="width:183px;">Fisher Chemical</td>
			<td style="width:124px;">G065015</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:347px;">H3BO3</td>
			<td style="width:183px;">AppliChem</td>
			<td style="width:124px;">A2940</td>
			<td>Dangerous substance. Please check manufacturer&#39;s safety instructions.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Heparin sodium salt</td>
			<td style="width:183px;">Sigma Aldrich</td>
			<td style="width:124px;">H3393-50KU</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Hygromycin B-solution</td>
			<td style="width:183px;">Roth</td>
			<td style="width:124px;">1287.2</td>
			<td>Dangerous substance.&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">KCl</td>
			<td style="width:183px;">VWR</td>
			<td style="width:124px;">26764298</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:347px;">KH2PO4</td>
			<td style="width:183px;">AppliChem</td>
			<td style="width:124px;">A3620</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:347px;">MgSO4 waterfree</td>
			<td style="width:183px;">Merck</td>
			<td style="width:124px;">7487-88-9</td>
			<td>Water free is critical. Alternatively use local supplier</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:347px;">MnCl2*4H2O</td>
			<td style="width:183px;">AppliChem</td>
			<td style="width:124px;">A2087</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">myo-Inositol</td>
			<td style="width:183px;">Sigma Aldrich</td>
			<td>I-5125</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:347px;">Na2-EDTA*2H2O</td>
			<td style="width:183px;">AppliChem</td>
			<td style="width:124px;">A2937</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:347px;">Na2MoO4*2H2O</td>
			<td style="width:183px;">Roth</td>
			<td style="width:124px;">0274.2</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:347px;">Na2SO4</td>
			<td style="width:183px;">Gr&#252;ssing GmbH</td>
			<td style="width:124px;">12174</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">NaCl</td>
			<td style="width:183px;">Fisher Chemical</td>
			<td style="width:124px;">S316060</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">NaOH</td>
			<td style="width:183px;">ChemSolute</td>
			<td style="width:124px;">13,751,000</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:347px;">NH4NO3</td>
			<td style="width:183px;">Roth</td>
			<td style="width:124px;">K299.1</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Nicotinic acid (Free Acid)</td>
			<td style="width:183px;">Sigma Aldrich</td>
			<td style="width:124px;">N-4126</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Nourseothricin dihydrogen sulfate&#160;&#160;</td>
			<td style="width:183px;">Werner BioAgents</td>
			<td style="width:124px;">5,001,000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">Nutrient broth&#160;</td>
			<td style="width:183px;">Difco</td>
			<td style="width:124px;"></td>
			<td>local suppliers</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:347px;">Phenol:Chloroform:Isoamyl Alcohol (25:24:1) pH 6.7</td>
			<td>Sigma Aldrich</td>
			<td>P3803</td>
			<td>Dangerous substance. Please check manufacturer&#39;s safety instructions.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">polyethylene glycol (PEG)</td>
			<td style="width:183px;">Sigma Aldrich</td>
			<td style="width:124px;">P-3640</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Potassium acetate</td>
			<td style="width:183px;">AppliChem</td>
			<td>121479</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">Pyridoxin (Monohydrochlorid)</td>
			<td style="width:183px;">Sigma Aldrich</td>
			<td style="width:124px;">P-9755</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">Riboflavin&#160;</td>
			<td style="width:183px;">Sigma Aldrich</td>
			<td style="width:124px;">R4500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">RNaseA</td>
			<td style="width:183px;">Sigma Aldrich</td>
			<td style="width:124px;">R5503</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">SDS</td>
			<td style="width:183px;">Roth</td>
			<td style="width:124px;">Cn30.3</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">small syringe</td>
			<td>BD</td>
			<td>300300</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">sterile filter, 22 &#181;m</td>
			<td>VWR</td>
			<td>28145-477</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">Sorbitol</td>
			<td style="width:183px;">Roth</td>
			<td style="width:124px;">6213.1</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">Thiamin-Hydrochloride</td>
			<td style="width:183px;">Serva</td>
			<td style="width:124px;">36020.02</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">tri-Na-Citrate</td>
			<td style="width:183px;">Fisher Chemical</td>
			<td style="width:124px;">S332060</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">Tris- (hydroxymethyl) aminomethane</td>
			<td>VWR</td>
			<td style="width:124px;">103156X</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">Tris hydrochloride</td>
			<td>Roth</td>
			<td style="width:124px;">9090.4</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Triton X-100&#160;</td>
			<td style="width:183px;">Serva&#160;</td>
			<td style="width:124px;">37240</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:347px;">ZnCl2</td>
			<td style="width:183px;">Fluka</td>
			<td style="width:124px;">96470</td>
			<td>alternatively use local supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">Name</td>
			<td style="width:183px;">Company</td>
			<td style="width:124px;">Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Composition of solutions/preparation of material</td>
			<td></td>
			<td></td>
			<td>Composition of solutions</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Carboxin</td>
			<td></td>
			<td></td>
			<td>Stock: 5 mg/ml in methanol, final concentration: 2 &#181;g/ml</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">CM plates</td>
			<td></td>
			<td></td>
			<td>0.25 % (w/v) Casamino acids, 0.1 % (w/v) Yeast Extract, 1.0 % (v/v) Holliday vitamin solution, 6.25 % (v/v); Holliday salt solution, 0.05 % (w/v) DNA degr. free acid, 0.15 % (w/v) NH4NO3, 2.0 % (w/v) Bacto Agar; adjust to pH 7.0 using 5 M NaOH; after autoclaving add 1 % glucose&#160;</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Geneticin (G418)</td>
			<td></td>
			<td></td>
			<td>Stock: 50 mg/ml in H2O, final concentration: 500 &#181;g/ml</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">HCl-washed glass beads (0,35-0,45 mm)</td>
			<td></td>
			<td></td>
			<td>Cover glass beads with concentrated HCl (25 %, 7.8 M) and incubate for 60 min. Sway several times. Decant HCl (keep decanted liquid) and wash glass beads with 3 M HCl (keep decanted liquid). Wash glass beads several times with double distilled H2O until the pH is 7 (the liquid should not be yellow-green anymore). Aliquot the glass beads and dry them at 180 &#176;C. The decanted HCl has to be neutralized before disposal.&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Heparin</td>
			<td></td>
			<td></td>
			<td>Stock: 15 mg/ml</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Holliday salt solution</td>
			<td></td>
			<td></td>
			<td>16.0 &#8240; (w/v) KH2PO4, 4.0 &#8240; (w/v) Na2SO4, 8.0 &#8240; (w/v) KCl, 1.32 &#8240; (w/v) CaCl2*2H2O, 8.0 &#8240; (v/v) trace elements, 2.0 &#8240; (w/v) MgSO4; sterile filtrate</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Holliday vitamin solution&#160;</td>
			<td></td>
			<td></td>
			<td>0.1&#8240; (w/v) Thiamin, 0.05&#8240; (w/v) Riboflavin, 0.05&#8240; (w/v) Pyridoxin, 0.2&#8240; (w/v) Ca-Pantothenat, (0.05&#8240; (w/v) Aminobenzoeic acid, 0.2&#8240; (w/v) Nicotinic acid, 0.2&#8240; (w/v) Cholinchlorid, 1.0&#8240; (w/v) myo-Inositol; may be stored at -20 &#176;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Hygromycin</td>
			<td></td>
			<td></td>
			<td>Stock: 50 mg/ml in PBS, final concentration: 200 &#181;g/ml</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Nourseothricin</td>
			<td></td>
			<td></td>
			<td>Stock: 200 mg/ml in H2O, final concentration: 150 &#181;g/ml</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NSY-glycerol-medium</td>
			<td></td>
			<td></td>
			<td>0.8 % (w/v) Nutrient Broth, 0.1 % (w/v) Yeast Extract, 0.5 % (w/v) Sucrose,&#160; 80.0 % (v/v) 87% Glycerin (f.c. 69.6%)&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">RegLight</td>
			<td></td>
			<td></td>
			<td>1.0% (w/v) Yeast Extract&#160; 0.4 % (w/v) Bacto Peptone, 0.4 % (w/v) Sucrose, 18.22 % (w/v) Sorbitol, 1.5 % (w/v) Agar</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">SCS, pH 5.8</td>
			<td></td>
			<td></td>
			<td>Solution 1: 20 mM tri-Na-citrate, 1 M Sorbitol; colution 2: 20 mM Citric acid, 1 M Sorbitol, add solution 2 into solution 1 until pH 5.8 is reached; autoclave</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">STC, pH 8</td>
			<td></td>
			<td></td>
			<td>1 M Sorbitol, 10 mM Tris-HCl pH 7.5, 100 mM CaCl2; filter sterile</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">STC/PEG</td>
			<td></td>
			<td></td>
			<td>40 % (v/v) PEG in STC-buffer&#160;</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">TE buffer, pH 8</td>
			<td></td>
			<td></td>
			<td>1.31 mM Tris-Base, 8.69 mM Tris-HCl, 10 mM Na2-EDTA*2H2O</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">TE/RNase</td>
			<td></td>
			<td></td>
			<td>10 &#181;g/ml RNaseA in TE buffer</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Trace elements</td>
			<td></td>
			<td></td>
			<td>0.06&#8240; (w/v) H3BO3, 0.14&#8240; (w/v) MnCl*4H2O, 0.4 &#8240; (w/v) ZnCl2, 0.4 &#8240; (w/v) Na2MoO4*2H2O, 0.1 &#8240; (w/v) FeCl3*6H2O, 0.04&#8240; (w/v) CuSO4*5H2O</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Trichoderma lysing enzymes solution</td>
			<td></td>
			<td></td>
			<td>12.5 mg/ml SCS; filter sterile; prepare shortly before use</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tris-HCl pH 7.5</td>
			<td></td>
			<td></td>
			<td>806 mM Tris-HCl, 194 mM Tris-Base; check the pH and if necessary adjust with HCl; autoclave</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Usti-lysis buffer 1, pH 8</td>
			<td></td>
			<td></td>
			<td>10 mM Tris-HCl (pH 8.0), 10 mM NaCl, 1 % (w/v) SDS, 2 % (v/v) TritonX-100, 1 mM EDTA. Do not measure pH using pH meter.&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Usti-lysis buffer 2</td>
			<td></td>
			<td></td>
			<td>mix Usti lysis buffer 1 with 1 x TE in a 1:1 ratio</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">YEPS-Light medium</td>
			<td></td>
			<td></td>
			<td>1.0% (w/v) Yeast Extract, 0.4% (w/v) Bacto Peptone, 0.4% (w/v) Sucrose, for plates: 1.5% (w/v) Bacto Agar</td>
		</tr>
	</tbody>
</table>

genetic manipulation of the plant pathogen ustilago maydis to study fungal biology and plant microbe interactions

Gene deletion plays an important role in the analysis of gene function. One of the most efficient methods to disrupt genes in a targeted manner is the replacement of the entire gene with a selectable marker via homologous recombination. During homologous recombination, exchange of DNA takes place between sequences with high similarity. Therefore, linear genomic sequences flanking a target gene can be used to specifically direct a selectable marker to the desired integration site. Blunt ends of the deletion construct activate the cell&#39;s DNA repair systems and thereby promote integration of the construct either via homologous recombination or by non-homologous-end-joining. In organisms with efficient homologous recombination, the rate of successful gene deletion can reach more than 50% making this strategy a valuable gene disruption system. The smut fungus Ustilago maydis is a eukaryotic model microorganism showing such efficient homologous recombination. Out of its about 6,900 genes, many have been functionally characterized with the help of deletion mutants, and repeated failure of gene replacement attempts points at essential function of the gene. Subsequent characterization of the gene function by tagging with fluorescent markers or mutations of predicted domains also relies on DNA exchange via homologous recombination. Here, we present the U. maydis strain generation strategy in detail using the simplest example, the gene deletion.

The deletion constructs for all four chitinolytic genes encoded in the U. maydis genome were generated by Golden Gate cloning using the hygR cassette for deletion of cts1, the natR for deletion of cts2, the G418R cassette for deletion of cts3 and the cbxR for deletion of cts4 20. A general overview of the gene replacement strategy is exemplified by the deletion of cts3 (Figure 1</s...

Watch this Scientific Journal Video about Genetic Manipulation of the Plant Pathogen Ustilago maydis to Study Fungal Biology and Plant Microbe Interactions at JoVE.com

Genetic Manipulation of the Plant Pathogen Ustilago maydis to Study Fungal Biology and Plant Microbe Interactions

We describe a robust gene replacement strategy to genetically manipulate the smut fungus Ustilago maydis. This protocol explains how to generate deletion mutants to investigate infection phenotypes. It can be extended to modify genes in any desired way, e.g., by adding a sequence encoding a fluorescent protein tag.

Genetic Manipulation of the Plant Pathogen Ustilago maydis to Study Fungal Biology and Plant Microbe Interactions

Gene deletion plays an important role in the analysis of gene function. One of the most efficient methods to disrupt genes in a targeted manner is the ...

genetic-manipulation-plant-pathogen-ustilago-maydis-to-study-fungal

Research

JoVE Journal

Genetics

14.3K Views.  Heinrich-Heine University Düsseldorf. We describe a robust gene replacement strategy to genetically manipulate the smut fungus Ustilago maydis. This protocol explains how to generate deletion mutants to investigate infection phenotypes. It can be extended to modify genes in any desired way, e.g., by adding a sequence encoding a fluorescent protein tag.

Video: Genetic Manipulation of the Plant Pathogen Ustilago maydis to Study Fungal Biology and Plant Microbe Interactions

Assessment of DNA Contamination in RNA Samples Based on Ribosomal DNA

One method extensively used for the quantification of gene expression changes and transcript abundances is reverse-transcription quantitative real-time PCR (RT-qPCR). It provides accurate, sensitive, reliable, and reproducible results. Several factors can affect the sensitivity and specificity of RT-qPCR. Residual genomic DNA (gDNA) contaminating RNA samples is one of them. In gene expression analysis, non-specific amplification due to gDNA contamination will overestimate the abundance of transcript levels and can affect the RT-qPCR results. Generally, gDNA is detected by qRT-PCR using primer pairs annealing to intergenic regions or an intron of the gene of interest. Unfortunately, intron/exon annotations are not yet known for all genes from vertebrate, bacteria, protist, fungi, plant, and invertebrate metazoan species.
Here we present a protocol for detection of gDNA contamination in RNA samples by using ribosomal DNA (rDNA)-based primers. The method is based on the unique features of rDNA: their multigene nature, highly conserved sequences, and high frequency in the genome. Also as a case study, a unique set of primers were designed based on the conserved region of ribosomal DNA (rDNA) in the Poaceae family. The universality of these primer pairs was tested by melt curve analysis and agarose gel electrophoresis. Although our method explains how rDNA-based primers can be applied for the gDNA contamination assay in the Poaceae family,&#160;it could be easily used to other prokaryote and eukaryote species

Here, we present a protocol for tracing genomic DNA (gDNA) contamination in RNA samples. The presented method utilizes primers specific for the internal transcribed spacer region (ITS) of ribosomal DNA (rDNA) genes. The method is suited for reliable and sensitive detection of DNA contamination in most eukaryotes and prokaryotes.

One method extensively used for the quantification of gene expression changes and transcript abundances is reverse-transcription quantitative real-time ...

Purification of High Molecular Weight Genomic DNA from Powdery Mildew for Long-Read Sequencing

The powdery mildew fungi are a group of economically important fungal plant pathogens. Relatively little is known about the molecular biology and genetics of these pathogens, in part due to a lack of well-developed genetic and genomic resources. These organisms have large, repetitive genomes, which have made genome sequencing and assembly prohibitively difficult. Here, we describe methods for the collection, extraction, purification and quality control assessment of high molecular weight genomic DNA from one powdery mildew species, Golovinomyces cichoracearum. The protocol described includes mechanical disruption of spores followed by an optimized phenol/chloroform genomic DNA extraction. A typical yield was 7 &#181;g DNA per 150 mg conidia. The genomic DNA that is isolated using this procedure is suitable for long-read sequencing (i.e., &#62; 48.5 kbp). Quality control measures to ensure the size, yield, and purity of the genomic DNA are also described in this method. Sequencing of the genomic DNA of the quality described here will allow for the assembly and comparison of multiple powdery mildew genomes, which in turn will lead to a better understanding and improved control of this agricultural pathogen.

Described here is a method for the extraction, purification, and quality control of genomic DNA from the obligate biotrophic fungal pathogen, powdery mildew, for use in long-read genome sequencing.

The powdery mildew fungi are a group of economically important fungal plant pathogens. Relatively little is known about the molecular biology and genetics ...

The Nematode Caenorhabditis Elegans - A Versatile In Vivo Model to Study Host-microbe Interactions

We demonstrate a method using Caenorhabditis elegans as a model host to study microbial interaction. Microbes are introduced via the diet making the intestine the primary location for disease. The nematode intestine structurally and functionally mimics mammalian intestines and is transparent making it amenable to microscopic study of colonization. Here we show that pathogens can cause disease and death. We are able to identify microbial mutants that show altered virulence. Its conserved innate response to biotic stresses makes C. elegans an excellent system to probe facets of host innate immune interactions. We show that hosts with mutations in the dual oxidase gene cannot produce reactive oxygen species and are unable to resist microbial insult. We further demonstrate the versatility of the presented survival assay by showing that it can be used to study the effects of inhibitors of microbial growth. This assay may also be used to discover fungal virulence factors as targets for the development of novel antifungal agents, as well as provide an opportunity to further uncover host-microbe interactions. The design of this assay lends itself well to high throughput whole-genome screens, while the ability to cryo-preserve worms for future use makes it a cost-effective and attractive whole animal model to study.

The Nematode Caenorhabditis Elegans - A Versatile In Vivo Model to Study Host-microbe Interactions

Here, we present the nematode Caenorhabditis elegans as a versatile host model to study microbial interaction.

We demonstrate a method using Caenorhabditis elegans as a model host to study microbial interaction. Microbes are introduced via the diet making the ...

Robust DNA Isolation and High-throughput Sequencing Library Construction for Herbarium Specimens

Herbaria are an invaluable source of plant material that can be used in a variety of biological studies. The use of herbarium specimens is associated with a number of challenges including sample preservation quality, degraded DNA, and destructive sampling of rare specimens. In order to more effectively use herbarium material in large sequencing projects, a dependable and scalable method of DNA isolation and library preparation is needed. This paper demonstrates a robust, beginning-to-end protocol for DNA isolation and high-throughput library construction from herbarium specimens that does not require modification for individual samples. This protocol is tailored for low quality dried plant material and takes advantage of existing methods by optimizing tissue grinding, modifying library size selection, and introducing an optional reamplification step for low yield libraries. Reamplification of low yield DNA libraries can rescue samples derived from irreplaceable and potentially valuable herbarium specimens, negating the need for additional destructive sampling and without introducing discernible sequencing bias for common phylogenetic applications. The protocol has been tested on hundreds of grass species, but is expected to be adaptable for use in other plant lineages after verification. This protocol can be limited by extremely degraded DNA, where fragments do not exist in the desired size range, and by secondary metabolites present in some plant material that inhibit clean DNA isolation. Overall, this protocol introduces a fast and comprehensive method that allows for DNA isolation and library preparation of 24 samples in less than 13 h, with only 8 h of active hands-on time with minimal modifications.

This article demonstrates a detailed protocol for DNA isolation and high-throughput sequencing library construction from herbarium material including rescue of exceptionally poor-quality DNA.

Herbaria are an invaluable source of plant material that can be used in a variety of biological studies. The use of herbarium specimens is associated with ...

Exploring the Root Microbiome: Extracting Bacterial Community Data from the Soil, Rhizosphere, and Root Endosphere

The intimate interaction between plant host and associated microorganisms is crucial in determining plant fitness, and can foster improved tolerance to abiotic stresses and diseases. As the plant microbiome can be highly complex, low-cost, high-throughput methods such as amplicon-based sequencing of the 16S rRNA gene are often preferred for characterizing its microbial composition and diversity. However, the selection of appropriate methodology when conducting such experiments is critical for reducing biases that can make analysis and comparisons between samples and studies difficult. This protocol describes in detail a standardized methodology for the collection and extraction of DNA from soil, rhizosphere, and root samples. Additionally, we highlight a well-established 16S rRNA amplicon sequencing pipeline that allows for the exploration of the composition of bacterial communities in these samples, and can easily be adapted for other marker genes. This pipeline has been validated for a variety of plant species, including sorghum, maize, wheat, strawberry, and agave, and can help overcome issues associated with the contamination from plant organelles.

Here, we describe a protocol to obtain amplicon sequence data of soil, rhizosphere, and root endosphere microbiomes. This information can be used to investigate the composition and diversity of plant-associated microbial communities, and is suitable for the use with a wide range of plant species.

The intimate interaction between plant host and associated microorganisms is crucial in determining plant fitness, and can foster improved tolerance to ...

Maintaining Biological Cultures and Measuring Gene Expression in Aphis nerii: A Non-model System for Plant-insect Interactions

Aphids are excellent experimental models for a variety of biological questions ranging from the evolution of symbioses and the development of polyphenisms to questions surrounding insect's interactions with their host plants. Genomic resources are available for several aphid species, and with advances in the next-generation sequencing, transcriptomic studies are being extended to non-model organisms that lack genomes. Furthermore, aphid cultures can be collected from the field and reared in the laboratory for the use in organismal and molecular experiments to bridge the gap between ecological and genetic studies. Last, many aphids can be maintained in the laboratory on their preferred host plants in perpetual, parthenogenic life cycles allowing for comparisons of asexually reproducing genotypes. Aphis nerii, the milkweed-oleander aphid, provides one such model to study insect interactions with toxic plants using both organismal and molecular experiments. Methods for the generation and maintenance of the plant and aphid cultures in the greenhouse and laboratory, DNA and RNA extractions, microsatellite analysis, de novo transcriptome assembly and annotation, transcriptome differential expression analysis, and qPCR verification of differentially expressed genes are outlined and discussed here.

Maintaining Biological Cultures and Measuring Gene Expression in Aphis nerii: A Non-model System for Plant-insect Interactions

The aphid Aphis nerii colonizes on highly-defended plants in the dogbane family (Apocyanaceae) and provides numerous opportunities to study plant-insect interactions. Here, we present a series of protocols for the maintenance of plant and aphid cultures, and the generation and analysis of molecular and -omic data for A. nerii.

Aphids are excellent experimental models for a variety of biological questions ranging from the evolution of symbioses and the development of polyphenisms ...

Plant Growth and Agrobacterium-mediated Floral-dip Transformation of the Extremophyte Schrenkiella parvula

Schrenkiella parvula is an extremophyte adapted to various abiotic stresses, including multiple ion toxicity stresses. Despite high-quality genomic resources available to study how plants adapt to environmental stresses, its value as a functional genomics model and tool has been limited by the lack of a feasible transformation system. In this protocol, we report how to generate stable transgenic S. parvula lines using an Agrobacterium-mediated floral-dip method. We modified the transformation protocol used for A. thaliana to account for unique traits of S. parvula, such as an indeterminate flowering habit and a high epicuticular wax content on leaves. Briefly, S. parvula seeds were stratified at 4 &#176;C for five days before planting. Plants were grown at a photoperiod of a 14 h light and 10 h dark and a 130 &#181;mol m-2s-1 light intensity, at 22 &#176;C to 24 &#176;C. Eight to nine week-old plants with multiple inflorescences were selected for transformation. These inflorescences were dipped in an infiltration solution of Agrobacterium tumefaciens GV3101 carrying the pMP90RK plasmid. We performed two rounds of flower dipping with an interval of three to four weeks to increase the transformation efficiency. The T1 seeds were collected and dried for four weeks in a container with desiccants before germination to screen for candidate transformed lines. Resistance to BASTA was used to screen T1 plants. We sprayed the BASTA solution three times with an interval of three days starting at two week-old plants to reduce false positives. A BASTA drop test was performed on surviving individual plants to identify true positive transformants. The transformation efficiency was 0.033%, yielding 3&#8211;4 transgenic plants per 10,000 T1 seeds propagated.

Plant Growth and Agrobacterium-mediated Floral-dip Transformation of the Extremophyte Schrenkiella parvula

Agrobacterium-mediated transformation using a floral-dip method can be successfully employed to create stable transgenic lines of the extremophyte model Schrenkiella parvula. We present a protocol modified from that for Arabidopsis thaliana, considering different growth habits and physiological characteristics of the extremophyte.

Schrenkiella parvula is an extremophyte adapted to various abiotic stresses, including multiple ion toxicity stresses. Despite high-quality genomic ...

Using Ustilago maydis as a Trojan Horse for In Situ Delivery of Maize Proteins

Inspired by Homer&#180;s Trojan horse myth, we engineered the maize pathogen Ustilago maydis to deliver secreted proteins into the maize apoplast permitting in vivo phenotypic analysis. This method does not rely on maize transformation but exploits microbial genetics and secretory capabilities of pathogens. Herein, it allows inspection of in vivo delivered secreted proteins with high spatiotemporal resolution at different kinds of infection sites and tissues. The Trojan horse strategy can be utilized to transiently complement maize loss-of-function phenotypes, to functionally characterize protein domains, to analyze off-target protein effects, or to study onside protein overdosage, making it a powerful tool for protein studies in the maize crop system. This work contains a precise protocol on how to generate a Trojan horse strain followed by standardized infection protocols to apply this method to three different maize tissue types.

Using Ustilago maydis as a Trojan Horse for In Situ Delivery of Maize Proteins

This work describes the cloning of an Ustilago maydis Trojan horse strain for the in situ delivery of secreted maize proteins into three different types of maize tissues.

Inspired by Homer&#180;s Trojan horse myth, we engineered the maize pathogen Ustilago maydis to deliver secreted proteins into the maize apoplast ...

CRISPR-mediated Genome Editing of the Human Fungal Pathogen Candida albicans

This method describes the efficient CRISPR mediated genome editing of the diploid human fungal pathogen Candida albicans. CRISPR-mediated genome editing in C. albicans requires Cas9, guide RNA, and repair template. A plasmid expressing a yeast codon optimized Cas9 (CaCas9) has been generated. Guide sequences directly upstream from a PAM site (NGG) are cloned into the Cas9 expression vector. A repair template is then made by primer extension in vitro. Cotransformation of the repair template and vector into C. albicans leads to genome editing. Depending on the repair template used, the investigator can introduce nucleotide changes, insertions, or deletions. As C. albicans is a diploid, mutations are made in both alleles of a gene, provided that the A and B alleles do not harbor SNPs that interfere with guide targeting or repair template incorporation. Multimember gene families can be edited in parallel if suitable conserved sequences exist in all family members. The C. albicans CRISPR system described is flanked by FRT sites and encodes flippase. Upon induction of flippase, the antibiotic marker (CaCas9) and guide RNA are removed from the genome. This allows the investigator to perform subsequent edits to the genome. C. albicans CRISPR is a powerful fungal genetic engineering tool, and minor alterations to the described protocols permit the modification of other fungal species including C. glabrata, N. castellii, and S. cerevisiae.

CRISPR-mediated Genome Editing of the Human Fungal Pathogen Candida albicans

Efficient genome engineering of Candida albicans is critical to understanding the pathogenesis and development of therapeutics. Here, we described a protocol to quickly and accurately edit the C. albicans genome using CRISPR. The protocol allows investigators to introduce a wide variety of genetic modifications including point mutations, insertions, and deletions.

This method describes the efficient CRISPR mediated genome editing of the diploid human fungal pathogen Candida albicans. CRISPR-mediated genome editing ...

A Bioinformatics Pipeline to Accurately and Efficiently Analyze the MicroRNA Transcriptomes in Plants

MicroRNAs (miRNAs) are 20- to 24-nucleotide (nt) endogenous small RNAs (sRNAs) extensively existing in plants and animals that play potent roles in regulating gene expression at the post-transcriptional level. Sequencing sRNA libraries by Next Generation Sequencing (NGS) methods has been widely employed to identify and analyze miRNA transcriptomes in the last decade, resulting in a rapid increase of miRNA discovery. However, two major challenges arise in plant miRNA annotation due to increasing depth of sequenced sRNA libraries as well as the size and complexity of plant genomes. First, many other types of sRNAs, in particular, short interfering RNAs (siRNAs) from sRNA libraries, are erroneously annotated as miRNAs by many computational tools. Second, it becomes an extremely time-consuming process for analyzing miRNA transcriptomes in plant species with large and complex genomes. To overcome these challenges, we recently upgraded miRDeep-P (a popular tool for miRNA transcriptome analyses) to miRDeep-P2 (miRDP2 for short) by employing a new filtering strategy, overhauling the scoring algorithm and incorporating newly updated plant miRNA annotation criteria. We tested miRDP2 against sequenced sRNA populations in five representative plants with increasing genomic complexity, including Arabidopsis, rice, tomato, maize and wheat. The results indicate that miRDP2 processed these tasks with very high efficiency. In addition, miRDP2 outperformed other prediction tools regarding sensitivity and accuracy. Taken together, our results demonstrate miRDP2 as a fast and accurate tool for analyzing plant miRNA transcriptomes, therefore a useful tool in helping the community better annotate miRNAs in plants.

A bioinformatics pipeline, namely miRDeep-P2 (miRDP2 for short), with updated plant miRNA criteria and an overhauled algorithm, could accurately and efficiently analyze microRNA transcriptomes in plants, especially for species with complex and large genomes.

MicroRNAs (miRNAs) are 20- to 24-nucleotide (nt) endogenous small RNAs (sRNAs) extensively existing in plants and animals that play potent roles in ...

Genetic Manipulation of the Plant Pathogen Ustilago maydis to Study Fungal Biology and Plant Microbe Interactions

Summary

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Chapters in this video

Assessment of DNA Contamination in RNA Samples Based on Ribosomal DNA

Purification of High Molecular Weight Genomic DNA from Powdery Mildew for Long-Read Sequencing

The Nematode Caenorhabditis Elegans - A Versatile In Vivo Model to Study Host-microbe Interactions

Robust DNA Isolation and High-throughput Sequencing Library Construction for Herbarium Specimens

Exploring the Root Microbiome: Extracting Bacterial Community Data from the Soil, Rhizosphere, and Root Endosphere

Maintaining Biological Cultures and Measuring Gene Expression in Aphis nerii: A Non-model System for Plant-insect Interactions

Plant Growth and Agrobacterium-mediated Floral-dip Transformation of the Extremophyte Schrenkiella parvula

Using Ustilago maydis as a Trojan Horse for In Situ Delivery of Maize Proteins

CRISPR-mediated Genome Editing of the Human Fungal Pathogen Candida albicans

A Bioinformatics Pipeline to Accurately and Efficiently Analyze the MicroRNA Transcriptomes in Plants