Name: genetic engineering of an unconventional yeast for renewable biofuel and biochemical production
Uploaded: 2016-09-20T08:00:00
Description: Watch this Scientific Journal Video about Genetic Engineering of an Unconventional Yeast for Renewable Biofuel and Biochemical Production at JoVE.com

We gratefully acknowledge the funding support from the National Environment Agency of Singapore (ETRP 1201102), the Competitive Research Program of the National Research Foundation of Singapore (NRF-CRP5-2009-03), the Agency for Science, Technology and Research of Singapore (1324004108), Global R&#38;D Project Program, the Ministry of Knowledge Economy, the Republic of Korea (N0000677), the Defense Threat Reduction Agency (DTRA, HDTRA1-13-1-0037) and the Synthetic Biology Initiative of the National University of Singapore (DPRT/943/09/14).

1. Generation of the Y. lipolytica KU70 Deletion Strain
<ol>
	<li>Construction of the disruption cassette 
	Note: See Table 1 for all primers used in polymerase chain reaction (PCR) amplifications.
	<ol>
		<li>Design primers 20 to PCR amplify the LEU2 expression cassette (see Table 1) from a Y. lipolytica expression vector and introduce LoxP sites into the 5&#39; and 3&#39; ends of the LEU2 cassette with a long forward primer...

<ol>
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Current research, technology and education topics in applied microbiology and microbial biotechnology. , 930-940 (2010).</li><li>Martinez-Vazquez, A., 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=Identification+of+the+transcription+factor+Znc1p,+which+regulates+the+yeast-to-hypha+transition+in+the+dimorphic+yeast+Yarrowia+lipolytica.">Identification of the transcription factor Znc1p, which regulates the yeast-to-hypha transition in the dimorphic yeast Yarrowia lipolytica.</a> Plos One. 8 (6), e66790 (2013).</li><li>Richard, M., Quijano, R. 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S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Food-related+applications+of+Yarrowia+lipolytica.">Food-related applications of Yarrowia lipolytica.</a> Food Chem. 152, 1-10 (2014).</li><li>Finogenova, T., Morgunov, I., Kamzolova, S., Chernyavskaya, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Organic+acid+production+by+the+yeast+Yarrowia+lipolytica:+a+review+of+prospects.">Organic acid production by the yeast Yarrowia lipolytica: a review of prospects.</a> Appl. Biochem. 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Our objective for this study is to enable quick and efficient generation of targeted gene knockouts in the Y. lipolytica Po1g strain. Several considerations need to be addressed to achieve this. First, a high transformation efficiency is required. Thus, an efficient and convenient chemical transformation protocol for the Y. lipolytica Po1g strain was described in this study. The use of PEG-4000 is a critical factor for the successful transformation of this strain. No transformants were obtained...

Unlike Saccharomyces cerevisiae, Yarrowia lipolytica, an unconventional yeast, can grow in the form of yeast or mycelium in response to changes in environmental conditions 1,2. Thus, this dimorphic yeast can be used as a good model for the study of fungal differentiation, morphogenesis and taxonomy 3,4,5. It is generally regarded as a safe (GRAS) yeast species, which is widely used to produce a variety of food additives such as organic acids, polyalcohols, aroma compounds, emulsifiers and surfactants 6,7,8,9. It is an obligate aerobe and a well-known oleaginous yeast capable of naturally accumulating lipids at high amounts, i.e., up to 70% of cell dry weight 10. It can also utilize a wide spectrum of carbon sources for growth, including different kinds of residues in waste resources as nutrients 11,12,13. All of these unique features make Y. lipolytica very attractive for various biotechnological applications.
Although the whole genome sequence of the Y. lipolytica has been published 14,15, genetic manipulation of this unconventional yeast is more complex than other yeast species. First, transformation of this yeast species is much less efficient due to the absence of a stable and efficient genetic transformation system 16,17. Second, laborious genomic integration of linear expression cassettes is commonly used for the expression of genes of interest as no natural episomal plasmid system has been found in this yeast 18. Third, generation of genetic knock-outs and knock-ins are limited because the gene targeting efficiency via accurate homologous recombination in this yeast is low and most integration events occur through non-homologous end joining (NHEJ) 19.
In this study, we report an optimized transformation protocol for the Y. lipolytica Po1g strain, which is easy, rapid, efficient and reproducible. To enhance the frequency of precise homologous recombination, we deleted the KU70 gene, which encodes a key enzyme in the NHEJ pathway. By using the optimized transformation protocol and transforming a linear knockout cassette containing flanking homology regions of 1 kb, the KU70 gene of the Y. lipolytica Po1g was successfully deleted. The robustness of this gene deletion methodology was then demonstrated by targeting alcohol dehydrogenase and alcohol oxidase genes in the Po1g KU70&#916; strain. It was observed that the KU70 deletion strain exhibited a considerably higher efficiency of homologous recombination-mediated gene targeting than that of the wild-type Po1g strain. In addition, a replicative Cre expression plasmid carrying the hygromycin B resistance marker was constructed to perform marker rescue. The marker rescue facilitates multiple rounds of gene targeting in the obtained gene deletion mutants. Besides gene deletion, our protocol for genetic transformation and gene deletion described here can be applied to insert genes to specific loci, and to introduce site-specific mutations into the Y. lipolytica genome.

<table border="0" cellpadding="0" cellspacing="0" width="605">
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:140px;">Reagent/Material</td>
			<td colspan="3" style="width:465px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Oligonucleotide primers</td>
			<td>Integrated DNA Technologies</td>
			<td></td>
			<td>25 nmole&#160; DNA oligos</td>
		</tr>
		<tr height="30">
			<td height="30" style="height:30px;">Y. lipolytica strain Po1g</td>
			<td>Yeastern Biotech</td>
			<td></td>
			<td style="width:207px;">leucine auxotrophic derivative of the wild-type strain W29 (ATCC 20460)</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Vector pYLEX1</td>
			<td>Yeastern Biotech</td>
			<td>FYY203-5MG</td>
			<td>Y. lipolytica expression vector&#160;</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">E. coli TOP10&#160;</td>
			<td>Invitrogen</td>
			<td></td>
			<td>For cloning and propagation of plasmids</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">pGEM-T vector&#160;</td>
			<td>Promega</td>
			<td>A3600</td>
			<td>TA cloning vector</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">QIAprep Spin Miniprep Kit</td>
			<td>Qiagen</td>
			<td>27106</td>
			<td>For plasmid isolation</td>
		</tr>
		<tr height="45">
			<td height="45" style="height:45px;width:140px;">Wizard SV Gel and 
			PCR Clean-Up System</td>
			<td>Promega</td>
			<td>A9282</td>
			<td style="width:207px;">Extract DNA fragments from agarose gels 
			and purify PCR products from an amplification reaction</td>
		</tr>
		<tr height="30">
			<td height="30" style="height:30px;width:140px;">The iProof high-fidelity 
			DNA polymerase</td>
			<td>Bio-Rad</td>
			<td>172-5302</td>
			<td>High-fidelity DNA polymerase</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">BamHI&#160;</td>
			<td>New England Biolabs</td>
			<td>R0136S</td>
			<td>Restriction enzyme</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">BglII&#160;</td>
			<td>New England Biolabs</td>
			<td>R0144L</td>
			<td>Restriction enzyme</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">KpnI</td>
			<td>New England Biolabs</td>
			<td>R0142S</td>
			<td>Restriction enzyme</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">NdeI&#160;</td>
			<td>New England Biolabs</td>
			<td>R0111S</td>
			<td>Restriction enzyme</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">NotI</td>
			<td>New England Biolabs</td>
			<td>R0189L</td>
			<td>Restriction enzyme</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">PmlI</td>
			<td>New England Biolabs</td>
			<td>R0532S</td>
			<td>Restriction enzyme</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">PstI&#160;</td>
			<td>New England Biolabs</td>
			<td>R0140S</td>
			<td>Restriction enzyme</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">SacII</td>
			<td>New England Biolabs</td>
			<td>R0157S</td>
			<td>Restriction enzyme</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">SalI</td>
			<td>New England Biolabs</td>
			<td>R0138S</td>
			<td>Restriction enzyme</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">XhoI</td>
			<td>New England Biolabs</td>
			<td>R0146L</td>
			<td>Restriction enzyme</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">T4 DNA ligase</td>
			<td>New England Biolabs</td>
			<td>M0202L</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Taq DNA polymerase&#160;</td>
			<td>Bio-Rad</td>
			<td>M0267L</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Ampicillin</td>
			<td>Gibco-Life Technologies</td>
			<td>11593-027</td>
			<td>Antibiotics</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Hygromycin B</td>
			<td>PAA</td>
			<td>P21-014</td>
			<td>Antibiotics</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">GeneRuler 1 kb DNA ladder</td>
			<td>Thermo Scientific</td>
			<td>SM0312</td>
			<td>1 kb DNA ladder</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">PEG4000</td>
			<td>Sigma</td>
			<td>95904-F</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Tris</td>
			<td>Promega</td>
			<td>H5135</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">EDTA</td>
			<td>Bio-Rad</td>
			<td>161-0729</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Salmon Sperm DNA</td>
			<td>Invitrogen</td>
			<td>15-632-011</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Lithium Acetate</td>
			<td>Sigma</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Acetic acid</td>
			<td>Sigma</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Glass beads (425-600 &#181;m)</td>
			<td>Sigma</td>
			<td>G8772</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">RNAse A</td>
			<td>Thermo Scientific</td>
			<td>EN0531</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">DNA Loading Dye</td>
			<td>Thermo Scientific</td>
			<td>R0611</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Bacto Yeast Extract</td>
			<td>BD</td>
			<td>212750</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Bacto Peptone</td>
			<td>BD</td>
			<td>211677</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">D-Glucose</td>
			<td>1st Base</td>
			<td>BIO-1101</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">YNB without amino acids</td>
			<td>Sigma</td>
			<td>Y0626</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">DO Supplement-Leu</td>
			<td>Clontech</td>
			<td>630414</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Glycerol</td>
			<td>Sigma</td>
			<td>G5516</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Difco LB Broth</td>
			<td>BD</td>
			<td>244620</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Difco LB Agar</td>
			<td>BD</td>
			<td>244520</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Bacto Agar</td>
			<td>BD</td>
			<td>214010</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">PCR machine</td>
			<td>Biorad</td>
			<td>T100 Thermal Cycler</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Water bath</td>
			<td>Memmert</td>
			<td>WNB 14</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Stationary/Shaking Incubator</td>
			<td>Yihder</td>
			<td>LM-570RD</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Thermo-shaker</td>
			<td>Allsheng</td>
			<td>MS-100</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Micro centrifuge</td>
			<td>Eppendorf</td>
			<td>5424R</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Centrifuge</td>
			<td>Eppendorf</td>
			<td>5810R</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Spectrophotometer</td>
			<td>Eppendorf&#160;</td>
			<td>BioPhotometer plus</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Gel imager</td>
			<td>GE</td>
			<td colspan="2">Amersham Imager 600</td>
		</tr>
	</tbody>
</table>

genetic engineering of an unconventional yeast for renewable biofuel and biochemical production

Yarrowia lipolytica is a non-pathogenic, dimorphic and strictly aerobic yeast species. Owing to its distinctive physiological features and metabolic characteristics, this unconventional yeast is not only a good model for the study of the fundamental nature of fungal differentiation but is also a promising microbial platform for biochemical production and various biotechnological applications, which require extensive genetic manipulations. However, genetic manipulations of Y. lipolytica have been limited due to the lack of an efficient and stable genetic transformation system as well as very high rates of non-homologous recombination that can be mainly attributed to the KU70 gene. Here, we report an easy and rapid protocol for the efficient genetic transformation and for gene deletion in Y. lipolytica Po1g. First, a protocol for the efficient transformation of exogenous DNA into Y. lipolytica Po1g was established. Second, to achieve the enhanced double-crossover homologous recombination rate for further deletion of target genes, the KU70 gene was deleted by transforming a disruption cassette carrying 1 kb homology arms. Third, to demonstrate the enhanced gene deletion efficiency after deletion of the KU70 gene, we individually deleted 11 target genes encoding alcohol dehydrogenase and alcohol oxidase using the same procedures on the KU70 knockout platform strain. It was observed that the rate of precise homologous recombination increased substantially from less than 0.5% for deletion of the KU70 gene in Po1g to 33%-71% for the single gene deletion of the 11 target genes in Po1g KU70&#916;. A replicative plasmid carrying the hygromycin B resistance marker and the Cre/LoxP system was constructed, and the selection marker gene in the yeast knockout strains was eventually removed by expression of Cre recombinase to facilitate multiple rounds of targeted genetic manipulations. The resulting single-gene deletion mutants have potential applications in biofuel and biochemical production.

The linearized Y. lipolytica expression vector was inserted into the pBR docking platform in the genome of Y. lipolytica Po1g strain by performing a single crossover recombination 27. By using the rapid chemical transformation procedure established in this study, the linearized Y. lipolytica expression vector was successfully transformed into the wild-type Po1g strain at a transformation efficiency of &#62;100 cfu/&#181;g DNA. A knockout cassette flan...

Watch this Scientific Journal Video about Genetic Engineering of an Unconventional Yeast for Renewable Biofuel and Biochemical Production at JoVE.com

Genetic Engineering of an Unconventional Yeast for Renewable Biofuel and Biochemical Production

We herein report methods on the molecular genetic manipulation of the Yarrowia lipolytica Po1g strain for improved gene deletion efficiency. The resulting engineered Y. lipolytica strains have potential applications in biofuel and biochemical production.

Yarrowia lipolytica is a non-pathogenic, dimorphic and strictly aerobic yeast species. Owing to its distinctive physiological features and metabolic ...

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