title: Identification and characterization of an efficient acyl-CoA: diacylglycerol acyltransferase 1 (DGAT1) gene from the microalga Chlorella ellipsoidea.
abstract: Oil in the form of triacylglycerols (TAGs) is quantitatively the most important storage form of energy for eukaryotic cells. Diacylglycerol acyltransferase (DGAT) is considered the rate-limiting enzyme for TAG accumulation. Chlorella, a unicellular eukaryotic green alga, has attracted much attention as a potential feedstock for renewable energy production. However, the function of DGAT1 in Chlorella has not been reported.
  
  
  
  A full-length cDNA encoding a putative diacylglycerol acyltransferase 1 (DGAT1, EC 2.3.1.20) was obtained from Chlorella ellipsoidea. The 2,142 bp open reading frame of this cDNA, designated CeDGAT1, encodes a protein of 713 amino acids showing no more than 40% identity with DGAT1s of higher plants. Transcript analysis showed that the expression level of CeDGAT1 markedly increased under nitrogen starvation, which led to significant triacylglycerol (TAG) accumulation. CeDGAT1 activity was confirmed in the yeast quadruple mutant strain H1246 by restoring its ability to produce TAG. Upon expression of CeDGAT1, the total fatty acid content in wild-type yeast (INVSc1) increased by 142%, significantly higher than that transformed with DGAT1s from higher plants, including even the oil crop soybean. The over-expression of CeDGAT1 under the NOS promoter in wild-type Arabidopsis thaliana and Brassica napus var. Westar significantly increased the oil content by 8-37% and 12-18% and the average 1,000-seed weight by 9-15% and 6-29%, respectively, but did not alter the fatty acid composition of the seed oil. The net increase in the 1,000-seed total lipid content was up to 25-50% in both transgenic Arabidopsis and B. napus.
  
  
  
  We identified a gene encoding DGAT1 in C. ellipsoidea and confirmed that it plays an important role in TAG accumulation. This is the first functional analysis of DGAT1 in Chlorella. This information is important for understanding lipid synthesis and accumulation in Chlorella and for genetic engineering to enhance oil production in microalgae and oil plants.
authors.affiliation: Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China.|University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Xuejie
authors.initials: X
authors.lastname: Guo
authors.affiliation: Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China.
authors.forename: Chengming
authors.initials: C
authors.lastname: Fan
authors.affiliation: Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China.
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Institute of Economical Crops, Yunnan Agricultural Academy, Kunming, 65023, China.
authors.forename: Jingqiao
authors.initials: J
authors.lastname: Wang
authors.affiliation: Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China.
authors.forename: Weibo
authors.initials: W
authors.lastname: Yin
authors.affiliation: United States Department of Agriculture, Agricultural Research Service, Forage and Range Research Laboratory, Utah State University, Logan, UT, 84322-6300, USA.
authors.forename: Richard R C
authors.initials: RR
authors.lastname: Wang
authors.affiliation: Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China. zmhu@genetics.ac.cn.|University of Chinese Academy of Sciences, Beijing, 100049, China. zmhu@genetics.ac.cn.|Present address: Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Datun Road, Chaoyang District, Beijing, 100101, China. zmhu@genetics.ac.cn.
authors.forename: Zanmin
authors.initials: Z
authors.lastname: Hu
mesh_terms: D000214:Acyl Coenzyme A; D017360:Arabidopsis; D029688:Brassica napus; D002708:Chlorella / Q000201:enzymology* / Q000235:genetics*; D051048:Diacylglycerol O-Acyltransferase / Q000235:genetics* / Q000378:metabolism; D017343:Genes, Plant; D050356:Lipid Metabolism; D009154:Mutation; D010802:Phylogeny; D010938:Plant Oils / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D012639:Seeds; D014280:Triglycerides / Q000378:metabolism
chemical_list: D000214:Acyl Coenzyme A; D010938:Plant Oils; D014280:Triglycerides; D051048:Diacylglycerol O-Acyltransferase
keywords: Chlorella ellipsoidea; Diacylglycerol acyltransferase; Nitrogen starvation; Seed oil content; Seed weight; Triacylglycerol