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Structural correlates of cytoplasmic and chloroplast lipid body synthesis in Chlamydomonas reinhardtii and stimulation of lipid body production with acetate boost.

ABSTRACT: Light microscopy and deep-etch electron microscopy were used to visualize triacylglyceride (TAG)-filled lipid bodies (LBs) of the green eukaryotic soil alga Chlamydomonas reinhardtii, a model organism for biodiesel production. Cells growing in nitrogen-replete media contain small cytoplasmic lipid bodies (?-cyto-LBs) and small chloroplast plastoglobules. When starved for N, ?-cyto-LB formation is massively stimulated. ?-Cyto-LBs are intimately associated with both the endoplasmic reticulum membrane and the outer membrane of the chloroplast envelope, suggesting a model for the active participation of both organelles in ?-cyto-LB biosynthesis and packaging. When sta6 mutant cells, blocked in starch biosynthesis, are N starved, they produce ?-cyto-LBs and also chloroplast LBs (cpst-LBs) that are at least 10 times larger than plastoglobules and eventually engorge the chloroplast stroma. Production of ?-cyto-LBs and cpst-LBs under the conditions we used is dependent on exogenous 20 mM acetate. We propose that the greater TAG yields reported for N-starved sta6 cells can be attributed to the strain's ability to produce cpst-LBs, a capacity that is lost when the mutant is complemented by a STA6 transgene. Provision of a 20 mM acetate "boost" during N starvation generates sta6 cells that become so engorged with LBs-at the expense of cytoplasm and most organelles-that they float on water even when centrifuged. This property could be a desirable feature for algal harvesting during biodiesel production.

SUBMITTER: Goodson C

PROVIDER: S-EPMC3232719 | biostudies-literature | 2011 Dec

REPOSITORIES: biostudies-literature

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Structural correlates of cytoplasmic and chloroplast lipid body synthesis in Chlamydomonas reinhardtii and stimulation of lipid body production with acetate boost.

Goodson Carrie C Roth Robyn R Wang Zi Teng ZT Goodenough Ursula U

Eukaryotic cell 20111028 12

Light microscopy and deep-etch electron microscopy were used to visualize triacylglyceride (TAG)-filled lipid bodies (LBs) of the green eukaryotic soil alga Chlamydomonas reinhardtii, a model organism for biodiesel production. Cells growing in nitrogen-replete media contain small cytoplasmic lipid bodies (α-cyto-LBs) and small chloroplast plastoglobules. When starved for N, β-cyto-LB formation is massively stimulated. β-Cyto-LBs are intimately associated with both the endoplasmic reticulum membr ...[more]

PMID: 22037181

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Project description:Large-scale mutant libraries have been indispensable for genetic studies, and the development of next-generation genome sequencing technologies has greatly advanced efforts to analyze mutants. In this work, we sequenced the genomes of 660 Chlamydomonas reinhardtii acetate-requiring mutants, part of a larger photosynthesis mutant collection previously generated by insertional mutagenesis with a linearized plasmid. We identified 554 insertion events from 509 mutants by mapping the plasmid insertion sites through paired-end sequences, in which one end aligned to the plasmid and the other to a chromosomal location. Nearly all (96%) of the events were associated with deletions, duplications, or more complex rearrangements of genomic DNA at the sites of plasmid insertion, and together with deletions that were unassociated with a plasmid insertion, 1470 genes were identified to be affected. Functional annotations of these genes were enriched in those related to photosynthesis, signaling, and tetrapyrrole synthesis as would be expected from a library enriched for photosynthesis mutants. Systematic manual analysis of the disrupted genes for each mutant generated a list of 253 higher-confidence candidate photosynthesis genes, and we experimentally validated two genes that are essential for photoautotrophic growth, CrLPA3 and CrPSBP4. The inventory of candidate genes includes 53 genes from a phylogenomically defined set of conserved genes in green algae and plants. Altogether, 70 candidate genes encode proteins with previously characterized functions in photosynthesis in Chlamydomonas, land plants, and/or cyanobacteria; 14 genes encode proteins previously shown to have functions unrelated to photosynthesis. Among the remaining 169 uncharacterized genes, 38 genes encode proteins without any functional annotation, signifying that our results connect a function related to photosynthesis to these previously unknown proteins. This mutant library, with genome sequences that reveal the molecular extent of the chromosomal lesions and resulting higher-confidence candidate genes, will aid in advancing gene discovery and protein functional analysis in photosynthesis.

Dataset Information

Structural correlates of cytoplasmic and chloroplast lipid body synthesis in Chlamydomonas reinhardtii and stimulation of lipid body production with acetate boost.

Publications

Structural correlates of cytoplasmic and chloroplast lipid body synthesis in Chlamydomonas reinhardtii and stimulation of lipid body production with acetate boost.

Similar Datasets

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