title: The pivotal role of malic enzyme in enhancing oil accumulation in green microalga Chlorella pyrenoidosa.
abstract: BACKGROUND
  The fast growing photosynthetic microalgae have been widely used in aquaculture, food, health, and biofuels. Recent findings in the diatom has proposed a pivotal role of NADP-malic enzyme in generation of NADPH as an important supply of reducing power for fatty acid biosynthesis. To test the lipogenic malic enzyme for fatty acid synthesis in green algae, here the malic enzyme gene PtME from the oleaginous diatom Phaeodactylum tricornutum was expressed in a representative green microalga Chlorella pyrenoidosa.
  
  
  RESULTS
  The engineered C. pyrenoidosa strain showed higher enzymatic activity of malic enzyme which subsequently promoted fatty acid synthesis. The neutral lipid content was significantly increased by up to 3.2-fold than wild type determined by Nile red staining, and total lipid content reached 40.9 % (dry cell weight). The engineered strain exhibited further lipid accumulation subjected to nitrogen deprivation condition. Upon nitrogen deprivation, engineered microalgae accumulated total lipid up to 58.7 % (dry cell weight), a 4.6-fold increase over the wild type cells under normal culture condition. At cellular level, increased volume and number of oil bodies were observed in the engineered microalgal cells.
  
  
  CONCLUSIONS
  These findings suggested that malic enzyme is a pivotal regulator in lipid accumulation in green microalga C. pyrenoidosa, and presenting a breakthrough of generating ideal algal strains for algal nutrition and biofuels.
authors.affiliation: Key Laboratory of Eutrophication and Red Tide Prevention of Guangdong Higher Education Institute, College of Life Science and Technology, Jinan University, Guangzhou, 510632, China.
authors.forename: Jiao
authors.initials: J
authors.lastname: Xue
authors.affiliation: Key Laboratory of Eutrophication and Red Tide Prevention of Guangdong Higher Education Institute, College of Life Science and Technology, Jinan University, Guangzhou, 510632, China.
authors.forename: Lan
authors.initials: L
authors.lastname: Wang
authors.affiliation: Key Laboratory of Eutrophication and Red Tide Prevention of Guangdong Higher Education Institute, College of Life Science and Technology, Jinan University, Guangzhou, 510632, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Eutrophication and Red Tide Prevention of Guangdong Higher Education Institute, College of Life Science and Technology, Jinan University, Guangzhou, 510632, China.
authors.forename: Srinivasan
authors.initials: S
authors.lastname: Balamurugan
authors.affiliation: Key Laboratory of Eutrophication and Red Tide Prevention of Guangdong Higher Education Institute, College of Life Science and Technology, Jinan University, Guangzhou, 510632, China.
authors.forename: Da-Wei
authors.initials: DW
authors.lastname: Li
authors.affiliation: Key Laboratory of Eutrophication and Red Tide Prevention of Guangdong Higher Education Institute, College of Life Science and Technology, Jinan University, Guangzhou, 510632, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Zeng
authors.affiliation: Key Laboratory of Eutrophication and Red Tide Prevention of Guangdong Higher Education Institute, College of Life Science and Technology, Jinan University, Guangzhou, 510632, China.
authors.forename: Wei-Dong
authors.initials: WD
authors.lastname: Yang
authors.affiliation: Key Laboratory of Eutrophication and Red Tide Prevention of Guangdong Higher Education Institute, College of Life Science and Technology, Jinan University, Guangzhou, 510632, China.
authors.forename: Jie-Sheng
authors.initials: JS
authors.lastname: Liu
authors.affiliation: Key Laboratory of Eutrophication and Red Tide Prevention of Guangdong Higher Education Institute, College of Life Science and Technology, Jinan University, Guangzhou, 510632, China. thyli@jnu.edu.cn.
authors.forename: Hong-Ye
authors.identifier: http://orcid.org/0000-0001-7427-0706
authors.initials: HY
authors.lastname: Li
mesh_terms: D002708:Chlorella / Q000201:enzymology* / Q000378:metabolism; D017377:Diatoms / Q000201:enzymology* / Q000235:genetics; D005227:Fatty Acids / Q000096:biosynthesis*; D050356:Lipid Metabolism; D008291:Malate Dehydrogenase / Q000235:genetics* / Q000378:metabolism*; D060847:Metabolic Engineering; D058086:Microalgae / Q000235:genetics* / Q000378:metabolism*
chemical_list: D005227:Fatty Acids; D008291:Malate Dehydrogenase; C031917:malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+)
keywords: Biofuel; Chlorella; Lipid accumulation; Malic enzyme