title: Stearoyl-acyl carrier protein desaturase gene from the oleaginous microalga Chlorella zofingiensis: cloning, characterization and transcriptional analysis.
abstract: The green alga Chlorella zofingiensis can accumulate high level of oleic acid (OA, C18:1△(9)) rich oils in response to stress conditions. To understand the regulation of biosynthesis of fatty acid in particular OA at the molecular level, we cloned and characterized the stearoyl acyl carrier protein (ACP) desaturase (SAD) responsible for OA formation through desaturation of stearic acid (C18:0) from C. zofingiensis. Southern blot indicated that the C. zofingiensis genome contained a single copy of SAD, from which the deduced amino acid sequence shared high identity to the corresponding homologs from other microalgae and higher plants. The desaturation activity of SAD was demonstrated in vitro using C18:0-ACP as a substrate. Stress conditions such as high light (HL), nitrogen deficiency (N(-)), or combination of HL and N(-) (HL + N(-)) drastically up-regulated the transcripts of biotin carboxylase (BC, a subunit of ACCase) and SAD, and therefore induced considerably the cellular accumulation of total fatty acids including OA. Glucose (50 mM) gave rise to the similar up-regulation of the two genes and induction of fatty acid accumulation. The accumulation of intracellular reactive oxygen species was found to be associated with the up-regulation of genes. This is the first report of characterization of Chlorella-derived SAD and the results may contribute to understanding of the mechanisms involved in fatty acid/lipid biosynthesis in microalgae.
authors.affiliation: Institute for Food and Bioresource Engineering, College of Engineering, Peking University, Beijing, China. gjinliu@asu.edu
authors.forename: Jin
authors.initials: J
authors.lastname: Liu
authors.forename: Zheng
authors.initials: Z
authors.lastname: Sun
authors.forename: Yujuan
authors.initials: Y
authors.lastname: Zhong
authors.forename: Junchao
authors.initials: J
authors.lastname: Huang
authors.forename: Qiang
authors.initials: Q
authors.lastname: Hu
authors.forename: Feng
authors.initials: F
authors.lastname: Chen
mesh_terms: D020418:Algal Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism / Q000528:radiation effects; D001483:Base Sequence; D002708:Chlorella / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects; D003001:Cloning, Molecular; D005227:Fatty Acids / Q000032:analysis / Q000378:metabolism* / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant; D005947:Glucose / Q000378:metabolism*; D008027:Light; D006899:Mixed Function Oxygenases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism / Q000528:radiation effects; D008969:Molecular Sequence Data; D009584:Nitrogen / Q000172:deficiency*; D019301:Oleic Acid / Q000378:metabolism; D010802:Phylogeny; D011401:Promoter Regions, Genetic; D017382:Reactive Oxygen Species / Q000032:analysis / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013229:Stearic Acids / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D020418:Algal Proteins; D005227:Fatty Acids; D017382:Reactive Oxygen Species; D013229:Stearic Acids; D019301:Oleic Acid; C031183:stearic acid; D006899:Mixed Function Oxygenases; C018747:acyl-(acyl-carrier-protein)desaturase; D005947:Glucose; D009584:Nitrogen