title: Enhancement of extraplastidic oil synthesis in Chlamydomonas reinhardtii using a type-2 diacylglycerol acyltransferase with a phosphorus starvation-inducible promoter.
abstract: When cultivated under stress conditions, many plants and algae accumulate oil. The unicellular green microalga Chlamydomonas reinhardtii accumulates neutral lipids (triacylglycerols; TAGs) during nutrient stress conditions. Temporal changes in TAG levels in nitrogen (N)- and phosphorus (P)-starved cells were examined to compare the effects of nutrient depletion on TAG accumulation in C. reinhardtii. TAG accumulation and fatty acid composition were substantially changed depending on the cultivation stage before nutrient starvation. Profiles of TAG accumulation also differed between N and P starvation. Logarithmic-growth-phase cells diluted into fresh medium showed substantial TAG accumulation with both N and P deprivation. N deprivation induced formation of oil droplets concomitant with the breakdown of thylakoid membranes. In contrast, P deprivation substantially induced accumulation of oil droplets in the cytosol and maintaining thylakoid membranes. As a consequence, P limitation accumulated more TAG both per cell and per culture medium under these conditions. To enhance oil accumulation under P deprivation, we constructed a P deprivation-dependent overexpressor of a Chlamydomonas type-2 diacylglycerol acyl-CoA acyltransferase (DGTT4) using a sulphoquinovosyldiacylglycerol 2 (SQD2) promoter, which was up-regulated during P starvation. The transformant strongly enhanced TAG accumulation with a slight increase in 18 : 1 content, which is a preferred substrate of DGTT4. These results demonstrated enhanced TAG accumulation using a P starvation-inducible promoter.
authors.affiliation: Center for Biological Resources and Informatics, Tokyo Institute of Technology, Midori-ku, Yokohama, Japan; Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Chiyoda-ku, Tokyo, Japan.
authors.forename: Masako
authors.initials: M
authors.lastname: Iwai
authors.forename: Keiko
authors.initials: K
authors.lastname: Ikeda
authors.forename: Mie
authors.initials: M
authors.lastname: Shimojima
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ohta
mesh_terms: D016825:Chlamydomonas reinhardtii / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D051048:Diacylglycerol O-Acyltransferase / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism; D066292:Lipid Droplets; D009584:Nitrogen / Q000172:deficiency; D010758:Phosphorus / Q000172:deficiency*; D010938:Plant Oils / Q000378:metabolism*; D018087:Plastids / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction; D014280:Triglycerides / Q000378:metabolism; D015854:Up-Regulation / Q000235:genetics
chemical_list: D005227:Fatty Acids; D010938:Plant Oils; D014280:Triglycerides; D010758:Phosphorus; D051048:Diacylglycerol O-Acyltransferase; D009584:Nitrogen
keywords: Chlamydomonas reinhardtii; algal biodiesel; diacylglycerol acyltransferase; nitrogen starvation; phosphorus starvation; triacylglycerol