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PMID:23161887
| Citation |
Li, X, Moellering, ER, Liu, B, Johnny, C, Fedewa, M, Sears, BB, Kuo, MH and Benning, C (2012) A galactoglycerolipid lipase is required for triacylglycerol accumulation and survival following nitrogen deprivation in Chlamydomonas reinhardtii. Plant Cell 24:4670-86 |
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| Abstract |
Following N deprivation, microalgae accumulate triacylglycerols (TAGs). To gain mechanistic insights into this phenomenon, we identified mutants with reduced TAG content following N deprivation in the model alga Chlamydomonas reinhardtii. In one of the mutants, the disruption of a galactoglycerolipid lipase-encoding gene, designated PLASTID GALACTOGLYCEROLIPID DEGRADATION1 (PGD1), was responsible for the primary phenotype: reduced TAG content, altered TAG composition, and reduced galactoglycerolipid turnover. The recombinant PGD1 protein, which was purified from Escherichia coli extracts, hydrolyzed monogalactosyldiacylglycerol into its lyso-lipid derivative. In vivo pulse-chase labeling identified galactoglycerolipid pools as a major source of fatty acids esterified in TAGs following N deprivation. Moreover, the fatty acid flux from plastid lipids to TAG was decreased in the pgd1 mutant. Apparently, de novo-synthesized fatty acids in Chlamydomonas reinhardtii are, at least partially, first incorporated into plastid lipids before they enter TAG synthesis. As a secondary effect, the pgd1 mutant exhibited a loss of viability following N deprivation, which could be avoided by blocking photosynthetic electron transport. Thus, the pgd1 mutant provides evidence for an important biological function of TAG synthesis following N deprivation, namely, relieving a detrimental overreduction of the photosynthetic electron transport chain. |
| Links |
PubMed PMC3531859 Online version:10.1105/tpc.112.105106 |
| Keywords |
Algal Proteins/genetics; Algal Proteins/metabolism; Carboxylic Ester Hydrolases/genetics; Carboxylic Ester Hydrolases/metabolism; Chlamydomonas reinhardtii/enzymology; Chlamydomonas reinhardtii/genetics; Chlamydomonas reinhardtii/physiology; Chlorophyll/metabolism; Fatty Acids/metabolism; Genetic Complementation Test; Lipid Metabolism; Lipids/analysis; Models, Biological; Mutation; Nitrogen/deficiency; Phenotype; Photosynthesis; Plastids/metabolism; Recombinant Proteins; Triglycerides/metabolism |
| edit table |
Significance
Annotations
| Gene product | Qualifier | GO Term | Evidence Code | with/from | Aspect | Extension | Notes | Status |
|---|---|---|---|---|---|---|---|---|
| GO:0047714: galactolipase activity |
ECO:0000315: |
F |
Figure 1 shows the accumulation of triacylglycerides in both wild type and mutants. In the mutant knockout strain, we see a much lower percentage of triacylglycerols in the total fatty acid content. This indicates that the protein has galactolipase function that, in this case, is important following nitrogen deprivation. |
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Notes
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