title: The green microalga Chlamydomonas reinhardtii has a single ω-3 fatty acid desaturase that localizes to the chloroplast and impacts both plastidic and extraplastidic membrane lipids.
abstract: The ω-3 polyunsaturated fatty acids account for more than 50% of total fatty acids in the green microalga Chlamydomonas reinhardtii, where they are present in both plastidic and extraplastidic membranes. In an effort to elucidate the lipid desaturation pathways in this model alga, a mutant with more than 65% reduction in total ω-3 fatty acids was isolated by screening an insertional mutant library using gas chromatography-based analysis of total fatty acids of cell pellets. Molecular genetics analyses revealed the insertion of a TOC1 transposon 113 bp upstream of the ATG start codon of a putative ω-3 desaturase (CrFAD7; locus Cre01.g038600). Nuclear genetic complementation of crfad7 using genomic DNA containing CrFAD7 restored the wild-type fatty acid profile. Under standard growth conditions, the mutant is indistinguishable from the wild type except for the fatty acid difference, but when exposed to short-term heat stress, its photosynthesis activity is more thermotolerant than the wild type. A comparative lipidomic analysis of the crfad7 mutant and the wild type revealed reductions in all ω-3 fatty acid-containing plastidic and extraplastidic glycerolipid molecular species. CrFAD7 was localized to the plastid by immunofluorescence in situ hybridization. Transformation of the crfad7 plastidial genome with a codon-optimized CrFAD7 restored the ω-3 fatty acid content of both plastidic and extraplastidic lipids. These results show that CrFAD7 is the only ω-3 fatty acid desaturase expressed in C. reinhardtii, and we discuss possible mechanisms of how a plastid-located desaturase may impact the ω-3 fatty acid content of extraplastidic lipids.
authors: Commissariat à l'Energie Atomique Cadarache, Institut de Biologie Environnementale et Biotechnologie, Laboratoire de Bioénergétique et Biotechnologie des Bactéries et Microalgues, Saint-Paul-lez-Durance F-13108, France.
authors: Hoa Mai
authors: HM
authors: Nguyen
authors: Stéphan
authors: S
authors: Cuiné
authors: Audrey
authors: A
authors: Beyly-Adriano
authors: Bertrand
authors: B
authors: Légeret
authors: Emmanuelle
authors: E
authors: Billon
authors: Pascaline
authors: P
authors: Auroy
authors: Fred
authors: F
authors: Beisson
authors: Gilles
authors: G
authors: Peltier
authors: Yonghua
authors: Y
authors: Li-Beisson
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics / Q000528:radiation effects; D000595:Amino Acid Sequence; D002467:Cell Nucleus / Q000235:genetics; D016825:Chlamydomonas reinhardtii / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects; D002736:Chloroplasts / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects; D004251:DNA Transposable Elements / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D044943:Fatty Acid Desaturases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015525:Fatty Acids, Omega-3 / Q000096:biosynthesis; D005455:Fluorescent Antibody Technique; D005816:Genetic Complementation Test; D056426:Genetic Loci / Q000235:genetics; D017403:In Situ Hybridization; D008027:Light; D008563:Membrane Lipids / Q000378:metabolism*; D058086:Microalgae / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects; D008954:Models, Biological; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional / Q000235:genetics; D009154:Mutation / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D013347:Subcellular Fractions / Q000201:enzymology; D013696:Temperature; D014158:Transcription, Genetic / Q000528:radiation effects; D014170:Transformation, Genetic
chemical_list: D004251:DNA Transposable Elements; D018744:DNA, Plant; D015525:Fatty Acids, Omega-3; D008563:Membrane Lipids; D044943:Fatty Acid Desaturases; C078565:omega-3 fatty acid desaturase
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