This study was supported by an Australian Research Council Centre of Excellence in Plant Energy Biology CE140100008, an Australian Research Council Future Fellowship (FT130100112) to MWM, and a Feodor Lynen Research Fellowship (Alexander von Humboldt Foundation, Germany) to JS.

This protocol is used for the isolation of intact mitochondria from Arabidopsis thaliana organs grown on soil using continuous colloidal density gradients. All procedures following the collection of the material are carried out at 4 &#176;C.
1. Preparation of Grinding Medium, Wash Buffer, and Gradient Solutions
<ol>
	<li>Prepare 300 mL of grinding medium (minus ascorbate and cysteine) and 200 mL of 2x wash buffer per Table 1 one day prior to the isolation, keep them...

<ol>
	<li>Day, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Highlights+in+plant+mitochondrial+research.+Methods+in+molecular+biology.">Highlights in plant mitochondrial research. Methods in molecular biology.</a> Plant mitochondria. 1305, v-xvi (2015).</li><li>Millar, A. H., Carrie, C., Pogson, B., Whelan, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Exploring+the+function-location+nexus:+Using+multiple+lines+of+evidence+in+defining+the+subcellular+location+of+plant+proteins.">Exploring the function-location nexus: Using multiple lines of evidence in defining the subcellular location of plant proteins.</a> Plant Cell. 21 (6), 1625-1631 (2009).</li><li>Eubel, H., 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=Free-flow+electrophoresis+for+purification+of+plant+mitochondria+by+surface+charge.">Free-flow electrophoresis for purification of plant mitochondria by surface charge.</a> Plant J. 52 (3), 583-594 (2007).</li><li>Murcha, M. W., 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=Protein+import+into+plant+mitochondria:+Signals,+machinery,+processing,+and+regulation.">Protein import into plant mitochondria: Signals, machinery, processing, and regulation.</a> J. Exp. Bot. 65 (22), 6301-6335 (2014).</li><li>Carrie, C., 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=Approaches+to+defining+dual-targeted+proteins+in+Arabidopsis.">Approaches to defining dual-targeted proteins in Arabidopsis.</a> Plant J. 57 (6), 1128-1139 (2009).</li><li>Pinto, G., Radulovic, M., Godovac-Zimmermann, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spatial+perspectives+in+the+redox+code+-+Mass+spectrometric+proteomics+studies+of+moonlighting+proteins.">Spatial perspectives in the redox code - Mass spectrometric proteomics studies of moonlighting proteins.</a> Mass Spectrom. Rev. , (2016).</li><li>Day, D. A., Neuburger, M., Douce, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biochemical+characterisation+of+chlorophyll-free+mitochondria+from+pea+leaves.">Biochemical characterisation of chlorophyll-free mitochondria from pea leaves.</a> Aust. J. Plant Physiol. 12 (3), 219-228 (1985).</li><li>Boersema, P. J., Raijmakers, R., Lemeer, S., Mohammed, S., Heck, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiplex+peptide+stable+isotope+dimethyl+labeling+for+quantitative+proteomics.">Multiplex peptide stable isotope dimethyl labeling for quantitative proteomics.</a> Nat. Protoc. 4 (4), 484-494 (2009).</li><li>Cheah, M. H., 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=Online+oxygen+kinetic+isotope+effects+using+membrane+inlet+mass+spectrometry+can+differentiate+between+oxidases+for+mechanistic+studies+and+calculation+of+their+contributions+to+oxygen+consumption+in+whole+tissues.">Online oxygen kinetic isotope effects using membrane inlet mass spectrometry can differentiate between oxidases for mechanistic studies and calculation of their contributions to oxygen consumption in whole tissues.</a> Anal Chem. 86 (10), 5171-5178 (2014).</li><li>Chrobok, 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=Dissecting+the+metabolic+role+of+mitochondria+during+developmental+leaf+senescence.">Dissecting the metabolic role of mitochondria during developmental leaf senescence.</a> Plant Physiol. 172 (4), 2132-2153 (2016).</li><li>Lee, C. P., Eubel, H., O'Toole, N., Millar, A. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Combining+proteomics+of+root+and+shoot+mitochondria+and+transcript+analysis+to+define+constitutive+and+variable+components+in+plant+mitochondria.">Combining proteomics of root and shoot mitochondria and transcript analysis to define constitutive and variable components in plant mitochondria.</a> Phytochemistry. 72 (10), 1092-1098 (2011).</li><li>Lee, C. P., Eubel, H., Solheim, C., Millar, A. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitochondrial+proteome+heterogeneity+between+tissues+from+the+vegetative+and+reproductive+stages+of+Arabidopsis+thaliana+development.">Mitochondrial proteome heterogeneity between tissues from the vegetative and reproductive stages of Arabidopsis thaliana development.</a> J. Proteome Res. 11 (6), 3326-3343 (2012).</li><li>Millar, A. H., Whelan, J., Soole, K. L., Day, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Organization+and+regulation+of+mitochondrial+respiration+in+plants.">Organization and regulation of mitochondrial respiration in plants.</a> Annu. Rev. Plant Biol. 62, 79-104 (2011).</li><li>Peters, K., 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=Complex+I+-+complex+II+ratio+strongly+differs+in+various+organs+of+Arabidopsis+thaliana.">Complex I - complex II ratio strongly differs in various organs of Arabidopsis thaliana.</a> Plant Mol. Biol. 79 (3), 273-284 (2012).</li><li>Werhahn, W. H., 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=Purification+and+characterization+of+the+preprotein+translocase+of+the+outer+mitochondrial+membrane+from+Arabidopsis+thaliana:+Identification+of+multiple+forms+of+TOM20.">Purification and characterization of the preprotein translocase of the outer mitochondrial membrane from Arabidopsis thaliana: Identification of multiple forms of TOM20.</a> Plant Physiol. 125 (2), 943-954 (2001).</li><li>Heazlewood, J. L., Howell, K. A., Whelan, J., Millar, A. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Towards+an+analysis+of+the+rice+mitochondrial+proteome.">Towards an analysis of the rice mitochondrial proteome.</a> Plant Physiol. 132 (1), 230-242 (2003).</li></ol>

The authors declare no conflict of interests.

Typically, isolation of mitochondria from Arabidopsis leaves yields up 3 mg of mitochondria from approximately 80 - 100 3 - 4-week old plants, although yields of greater than 5 mg can often be achieved with thorough grinding. The yield varies with growth conditions and decreases dramatically as leaves senesce, although mitochondria structure seems to be well maintained during senescence9. One of the most critical features to obtain a good yield is the method of grinding to lyse cells to release mi...

The history of plant mitochondrial research goes back over 100 years1. Intact mitochondria were first isolated in the early 1950s using differential centrifugation. The advent of a colloidal density gradient in the 1980s allowed mitochondria to be purified without suffering osmotic adjustment. While gradient purified mitochondria are suitable for most purposes, due to the sensitivity of mass spectrometry, even relatively minor contaminants can be detected and may be inappropriately assigned a mitochondrial location2. The use of free flow electrophoresis can remove both plastidic and peroxisome contamination3, but free flow electrophoresis is a highly specialized technique and is not required for the vast majority of studies. Furthermore, when determining the location of a protein it needs to be remembered that dual or multiple targeting of proteins occurs in cells. Over 100 dual targeted proteins are described for chloroplasts/plastids and mitochondria4, and a number of proteins targeted to mitochondria and peroxisomes are also known5. Furthermore, the re-location of proteins under specific stimuli, e.g. oxidative stress, is an emerging theme in cell biology6. Thus, the location of proteins needs to be considered in the context of the biology studied, and a variety of approaches are used to determine and verify location2.
Mitochondria are typically isolated from plant tissues by homogenization, a balance is required between breaking open the cell wall to release mitochondria, and not damaging the mitochondria. Traditionally, with potato and cauliflower, homogenization involves using household blender/juicer apparatus to make a liquid extract in a buffer with various components to maintain activity.&#160;Isolation of mitochondria from pea leaves, (a popular material for mitochondrial isolation using young seedlings (~10 days old), utilizes a blender to lyse cells as the leaf material is soft. With the availability of Arabidopsis thaliana T-DNA insertional knock-out lines, the need to be able to purify mitochondria to carry out functional studies has necessitated the development of methods to isolate mitochondria from leaf, root or flower tissue. Overall the methods developed for other plants worked well7, with the perquisite that grinding of the material needed to be optimized. For Arabidopsis this can be achieved in a variety of ways (see below), and differs between tissue types (root versus shoot). The use of the continuous gradient can also be optimized as the density of mitochondria from different organs or developmental stages means they can migrate differently. Thus, for maximum separation the density of the gradient can be refined to ensure to achieve best separation.
Once purified the mitochondria can be used for a variety of studies, including protein and tRNA uptake experiments, enzyme activity assays, respiratory chain measurements and western blot analyses. Isolated mitochondria can also be used for mass spectrometry analyses of protein abundance. Targeted multiple reaction monitoring (MRM) analyses allows for the quantification of defined proteins, but require significant assay development. In contrast, quantification by dimethyl or other isotope labels8, provides a discovery approach in identifying differences across the whole proteome that can be used to uncover novel biological insights.

<table>
	<tbody>
		<tr>
			<td>ADP</td>
			<td>Sigma-Aldrich</td>
			<td>A2754</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Antimycin A</td>
			<td>Sigma-Aldrich</td>
			<td>A8674</td>
			<td>Chemical, dissolve in ethanol</td>
		</tr>
		<tr>
			<td>AOX antibody</td>
			<td>from Tom Elthon</td>
			<td></td>
			<td>Elthon et al., 1989</td>
		</tr>
		<tr>
			<td>Ascorbate</td>
			<td>Sigma-Aldrich</td>
			<td>A0157</td>
			<td>Ascorbate Oxidase from Cucurbita sp.</td>
		</tr>
		<tr>
			<td>ATP</td>
			<td>Sigma-Aldrich</td>
			<td>A26209</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Bovine serum albumin (BSA)</td>
			<td>Bovogen</td>
			<td>BSAS 1.0</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Clarity western ECL substrate</td>
			<td>Bio-Rad Laboratories</td>
			<td>1705061</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Criterion Stain-Free Precast Gels 8-16% 18 Wells</td>
			<td>Bio-Rad Laboratories</td>
			<td>5678104</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Cyanide</td>
			<td>Sigma-Aldrich</td>
			<td>60178</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Cytochrome c</td>
			<td>Sigma-Aldrich</td>
			<td>C3131</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Difco Agar, granulated</td>
			<td>BD Biosciences</td>
			<td>214530</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Dithiotreitol</td>
			<td>Sigma-Aldrich</td>
			<td>D0632</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>EDTA disodium salt</td>
			<td>Sigma-Aldrich</td>
			<td>E5134</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Gamborg B-5 Basal Medium</td>
			<td>Austratec</td>
			<td>G398-100L</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Gamborg Vitamin Solution (1000x)</td>
			<td>Austratec</td>
			<td>G219-100ML</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Goat Anti-Mouse IgG (H + L)-HRP Conjugate</td>
			<td>Bio-Rad Laboratories</td>
			<td>1706516-2ml</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Goat Anti-Rabbit IgG (H + L)-HRP Conjugate</td>
			<td>Bio-Rad Laboratories</td>
			<td>1706515-2ml</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>L-Cysteine</td>
			<td>Sigma</td>
			<td>C7352-100G</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Magnesium sulfate</td>
			<td>Sigma-Aldrich</td>
			<td>230391</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Murashige &#38; Skoog Basal Salt Mixture (MS)</td>
			<td>Austratec</td>
			<td>M524-100L</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Myxothiazol</td>
			<td>Sigma-Aldrich</td>
			<td>T5580</td>
			<td>Chemical, dissolve in ethanol</td>
		</tr>
		<tr>
			<td>NADH</td>
			<td>Sigma-Aldrich</td>
			<td>N8129</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Ndufs4 antibody</td>
			<td>from Etienne Meyer</td>
			<td></td>
			<td>Meyer et al., 2009</td>
		</tr>
		<tr>
			<td>n-Propyl gallate</td>
			<td>Sigma-Aldrich</td>
			<td>P3130</td>
			<td>Chemical, dissolve in ethanol</td>
		</tr>
		<tr>
			<td>Percoll</td>
			<td>GE Healthcare</td>
			<td>17-0891-01</td>
			<td>Chemical, colloidal density gradient</td>
		</tr>
		<tr>
			<td>Polyvinylpyrrolidone (PVP40)</td>
			<td>Sigma-Aldrich</td>
			<td>PVP40</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Potassium cyanide</td>
			<td>Sigma-Aldrich</td>
			<td>60178</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Potassium phosphate monobasic (KH2PO4)</td>
			<td>Sigma-Aldrich</td>
			<td>P5655</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Pyruvate</td>
			<td>Sigma-Aldrich</td>
			<td>P2256</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Sodium chloride</td>
			<td>Chem-Supply</td>
			<td>SA046</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Sodium dithionite</td>
			<td>Sigma-Aldrich</td>
			<td>157953</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Sodium L-ascorbate</td>
			<td>Sigma</td>
			<td>A4034-100G</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Succinate</td>
			<td>Sigma-Aldrich</td>
			<td>S2378</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Chem-Supply</td>
			<td>SA030</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>TES</td>
			<td>Sigma-Aldrich</td>
			<td>T1375</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Tetrasodium pyrophosphate (Na4P2O7 &#183; 10H2O)</td>
			<td>Sigma-Aldrich</td>
			<td>221368</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Trans-Blot Turbo RTA Midi Nitrocellulose Transfer Kit</td>
			<td>Bio-Rad Laboratories</td>
			<td>1704271</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Triton-X 100</td>
			<td>Sigma-Aldrich</td>
			<td>X100</td>
			<td>Chemical, detergent</td>
		</tr>
		<tr>
			<td>Western Blocking Reagent</td>
			<td>Sigma</td>
			<td>11921681001</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Balance</td>
			<td>Mettler Toledo</td>
			<td>XS204</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Beakers</td>
			<td>Isolab</td>
			<td>50 mL</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Beckman Coulter</td>
			<td>Avanti J-26XP</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Centrifuge tubes</td>
			<td>Nalgene</td>
			<td>3117-9500</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Circulator</td>
			<td>Julabo</td>
			<td>1124971</td>
			<td>Attached to oxygen electrode chamber</td>
		</tr>
		<tr>
			<td>Conical flask</td>
			<td>Isolab</td>
			<td>500 mL</td>
			<td></td>
		</tr>
		<tr>
			<td>Dropper</td>
			<td></td>
			<td>3 mL</td>
			<td></td>
		</tr>
		<tr>
			<td>Fixed angle rotor</td>
			<td>Beckman Coulter</td>
			<td>JA25.5</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Funnel</td>
			<td>Per Alimenti</td>
			<td>14 cm</td>
			<td>For filtering</td>
		</tr>
		<tr>
			<td>Gradient pourer</td>
			<td>Bio-Rad</td>
			<td>165-4120</td>
			<td>For preparation of gradients</td>
		</tr>
		<tr>
			<td>Magnetic Stirrer ATE</td>
			<td>VELP Scientifica</td>
			<td>F20300165</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Miracloth</td>
			<td>VWR</td>
			<td>EM475855-1R</td>
			<td>Filtration material</td>
		</tr>
		<tr>
			<td>Mortar and pestle</td>
			<td>Jamie Oliver</td>
			<td>Granite, 6 Inch</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>O2view</td>
			<td>Hansatech Instruments</td>
			<td></td>
			<td>Oxygen monitoring software</td>
		</tr>
		<tr>
			<td>Oxygraph Plus System</td>
			<td>Hansatech Instruments</td>
			<td>1187253</td>
			<td>Clark-type oxygen electrode</td>
		</tr>
		<tr>
			<td>Paintbrush</td>
			<td>Artist first choice</td>
			<td>1008R-12</td>
			<td></td>
		</tr>
		<tr>
			<td>Parafilm</td>
			<td>Bemis</td>
			<td>PM-996</td>
			<td>plastic paraffin film</td>
		</tr>
		<tr>
			<td>Peristaltic pump</td>
			<td>Gilson</td>
			<td>F155001</td>
			<td>For preparation of gradients</td>
		</tr>
		<tr>
			<td>PVC peristaltic tubing</td>
			<td>Gilson</td>
			<td>F117930</td>
			<td>For preparation of gradients</td>
		</tr>
		<tr>
			<td>Water bath</td>
			<td>VELP Scientifica</td>
			<td>OCB</td>
			<td>Equipment</td>
		</tr>
	</tbody>
</table>

isolation and respiratory measurements of mitochondria from arabidopsis thaliana

Mitochondria are essential organelles involved in numerous metabolic pathways in plants, most notably the production of adenosine triphosphate (ATP) from the oxidation of reduced compounds such as nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FADH2). The complete annotation of the Arabidopsis thaliana genome has established it as the most widely used plant model system, and thus the need to purify mitochondria from a variety of organs (leaf, root, or flower) is necessary to fully utilize the tools that are now available for Arabidopsis to study mitochondrial biology. Mitochondria are isolated by homogenization of the tissue using a variety of approaches, followed by a series of differential centrifugation steps producing a crude mitochondrial pellet that is further purified using continuous colloidal density gradient centrifugation. The colloidal density material is subsequently removed by multiple centrifugation steps. Starting from 100 g of fresh leaf tissue, 2 - 3 mg of mitochondria can be routinely obtained. Respiratory experiments on these mitochondria display typical rates of 100 - 250 nmol O2 min-1 mg total mitochondrial protein-1 (NADH-dependent rate) with the ability to use various substrates and inhibitors to determine which substrates are being oxidized and the capacity of the alternative and cytochrome terminal oxidases. This protocol describes an isolation method of mitochondria from Arabidopsis thaliana leaves using continuous colloidal density gradients and an efficient respiratory measurements of purified plant mitochondria.

Using this protocol, we were able to detect different mitochondrial proteins by SDS-PAGE and immunoblotting. As shown in Figure 3A, the protein isolated from water culture tissue is sufficient to detect a faint band (2 &#181;g). Signal intensity increases proportionately to the amounts loaded. For mitochondria isolated from tissues grown on plates (Figure 3B), the response to high light stress treatment in different genotypes can...

Watch this Scientific Journal Video about Isolation and Respiratory Measurements of Mitochondria from Arabidopsis thaliana at JoVE.com

Isolation and Respiratory Measurements of Mitochondria from Arabidopsis thaliana

As mitochondria are only a small percentage of the plant cell, they need to be purified for a range of studies. Mitochondria can be isolated from a variety of plant organs by homogenization, followed by differential and density gradient centrifugation to obtain a highly purified mitochondrial fraction.

Isolation and Respiratory Measurements of Mitochondria from Arabidopsis thaliana

Mitochondria are essential organelles involved in numerous metabolic pathways in plants, most notably the production of adenosine triphosphate (ATP) from ...

The overall goal of isolating intact and pure plant mitochondria is to study respiration, mitochondrial composition, biogenesis, and metabolism. This method can help answer key questions in plant energy biology, such as the importance of mitochondria and stress tolerance, under changing environmental conditions. The main advantage of this technique is that sufficient quantities of pure, intact, and functional mitochondria could be isolated from relatively small quantities of plant tissue.Demonstrating the procedure will be Wenhui Lyu, and Jennifer Selinski, From my laboratory. On the day of mitochondrial isolation, wash the gradient pourer and PVC peristaltic tubing with deionized water to prepare the gradients. Incline to position two 50 mL centrifuge tubes on ice, such that the peristaltic tubing outlet touches the wall of the tubes.Then turn the black lever down to close the connection between the inner and outer chambers. Place the gradient pourer with the magnetic stir bar inside the inner chamber on a magnetic stirrer. Then, pour 35 mL of heavy gradient solution into the inner chamber.Dispense half of the heavy gradient solution through the peristaltic pump, at 300 mL per hour, into two centrifuge tubes, kept on ice. Then pour 35 mL of light gradient solution into the outer chamber. Immediately, turn the black lever up halfway to resume connection between the inner and the outer chambers, for the solutions to mix gently.Expel the entire gradient mixture from the chambers, at a rate of 60 mL per hour, to form two continuous 0%to 4.4%PVP gradients. Always keep the gradients on ice before use. It is important not to overground the plant tissue, otherwise the mitochondria will break down.For a single preparation, cut the whole rosette tissue from at least 80 four week old Arabidopsis plants, grown on soil. Then add half of the cut plant tissues to a cooled large mortar and pestle, containing 75 mL of grinding medium. Then use grinding medium to moisten four layers of filtration material, with a pore size of 20 to 25 m.Use a plastic funnel to filter the homogeny through all four layers of filtration material, and collect it in a 500 mL conical flask. Use an additional 75 mL of grinding medium to grind the other half of the tissue. Then combine the entire homogenate in the filtration material, to filter out as much as possible.Use 150 mL of grinding medium to grind all of the remaining tissue on the filtration material, and filter into a 500 mL conical flask. Distribute the filtered homogenate in eight pre-chilled 50mL plastic centrifuge tubes. And centrifuge at 2, 500 g at four degrees celsius, in a fixed angle rotor, for five minutes.After pouring the supernatant into clean centrifuge tubes, centrifuge again at 17, 500 g, at four degrees celsius, for 20 minutes, in a fixed angle rotor. Leave 3 mL of supernatant in the tube. Then use a fine paintbrush to gently re-suspend the pellet in the remaining supernatant.Add 10 mL of single strength wash buffer to each of the tubes, and pool all four of the tubes into one centrifuge tube, resulting in two tubes total. Adjust the volume to 50mL with single strength wash buffer, and repeat the centrifugation steps. Using a very small quantity of wash buffer, disperse the pellet with the fine paintbrush, and then use a dropper to pool the crude mitochondrial pellet into a tube.Then carefully layer the mitochondrial suspension with a dropper, on two continuous 0%to 4%PVP gradients. Use single strength wash buffer to balance the weight of the tubes, and conduct a centrifugation run at 40, 000 g at four degrees celsius, for 40 minutes. Remember to turn off the brake.Cautiously aspirate the upper five centimeters of solution above the mitochondrial band. Then distribute the mitochondrial solution into two clean tubes, and fill with single strength wash buffer. Cover the mouth of the tube with plastic paraffin film, and invert it several times to evenly distribute the colloidal density gradient, and mitochondria.Then, centrifuge at 31, 000 g for 15 minutes at four degrees celsius, with slow brake. Aspirate the supernatant and adjust the tube volume up to 50mL with single strength wash buffer. Invert several times for proper mixing.Centrifuge the solution at 31, 000 g for 15 minutes at four degrees celsius with slow brake. Aspirate the supernatant, and subsequently collect the mitochondrial pellet in 500 l of single strength wash buffer, using a pipette with modified 200 l tip. With the plunger open, add 970 l of air saturated respiration medium to the reaction chamber.Then add 150 g of total mitochondrial protein, using a modified pipette, and 500 M Adenosine Triphosphate to the reaction chamber, to determine mitochondrial respiration. Use a magnetic stir bar to continuously stir the mitochondrial suspension. After closing the plunger, click Start Recording to record oxygen consumption.Wait for a minute or two, to check for a linear oxygen consumption trace, indicating stable oxygen consumption. Then, add 5 mM of succinate, and record the oxygen consumption for approximately two minutes. Add 1 mM Adenosine Diphosphate, and keep recording the oxygen consumption rate for another two minutes.Next, add 1 mM Nicotinamide Adenine Dinucleotide Hydrogen, and continue recording oxygen consumption for around four to eight minutes. Then add reagents to inhibit the cytochrome C pathway, and keep recording the oxygen consumption via alternative oxidase, for about two minutes. KCN, myxothiazol, and antimycin A are all respiratory poisons.It is important to follow the safety instructions in the MSDS data sheets. Please note that different countries will have different legislations for the use of these inhibitors in our experiments. Next, add 5 mM dithiothreitol, and 10 mM pyruvate to activate the alternative oxidase.And keep recording for another five to seven minutes. Finally, add 500 mM N-propyl gallate, and record for two minutes. A representative gradient, showing the presence of greenish-white mitochondrial fraction near the bottom of the gradient solution.Thylakoids and other contaminants present on top of the gradient solution, are indicated in dark green bands. Representative traces of oxygen consumption by mitochondria, to show the outer membrane integrity before oxygen consumption measurement. The outer membrane integrity was well preserved and about 90%intact.Representative traces of oxygen consumption by mitochondria, after adding substrates, inhibitors, and effectors. The results show a compromised cytochrome c, and alternative oxidase pathway. After watching this video, you should have a good understanding of how to isolate and analyze plant mitochondria.

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15.1K Görüntüleme.  La Trobe University. The overall goal of isolating intact and pure plant mitochondria is to study respiration, mitochondrial composition, biogenesis, and metabolism. This method can help answer key questions in plant energy biology, such as the importance of mitochondria and stress tolerance, under changing environmental conditions. The main advantage of this technique is that sufficient quantities of pure, intact, and functional mitochondria could be isolated from relatively small quantities of plant tissue....