title: Effect of the expression and knockdown of citrate synthase gene on carbon flux during triacylglycerol biosynthesis by green algae Chlamydomonas reinhardtii.
abstract: BACKGROUND
  The regulation of lipid biosynthesis is essential in photosynthetic eukaryotic cells. This regulation occurs during the direct synthesis of fatty acids and triacylglycerols (TAGs), as well as during other controlling processes in the main carbon metabolic pathway.
  
  
  RESULTS
  In this study, the mRNA levels of Chlamydomonas citrate synthase (CrCIS) were found to decrease under nitrogen-limited conditions, which suggests suppressed gene expression. Gene silencing by RNA interference (RNAi) was conducted to determine whether CrCIS suppression affected the carbon flux in TAG biosynthesis. Results showed that the TAG level increased by 169.5%, whereas the CrCIS activities in the corresponding transgenic algae decreased by 16.7% to 37.7%. Moreover, the decrease in CrCIS expression led to the increased expression of TAG biosynthesis-related genes, such as acyl-CoA:diacylglycerol acyltransferase and phosphatidate phosphatase. Conversely, overexpression of CrCIS gene decreased the TAG level by 45% but increased CrCIS activity by 209% to 266% in transgenic algae.
  
  
  CONCLUSIONS
  The regulation of CrCIS gene can indirectly control the lipid content of algal cells. Our findings propose that increasing oil by suppressing CrCIS expression in microalgae is feasible.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Deng
authors.forename: Jiajia
authors.initials: J
authors.lastname: Cai
authors.affiliation: School of Science, Hainan Medical College, Haikou 571101, China. feixw2000@hotmail.com.
authors.forename: Xiaowen
authors.initials: X
authors.lastname: Fei
mesh_terms: D018533:Biomass; D002244:Carbon / Q000378:metabolism*; D016825:Chlamydomonas reinhardtii / Q000201:enzymology*; D002950:Citrate (si)-Synthase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D019295:Computational Biology; D051048:Diacylglycerol O-Acyltransferase / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D009584:Nitrogen / Q000378:metabolism; D010711:Phosphatidate Phosphatase / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000201:enzymology; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D014280:Triglycerides / Q000096:biosynthesis*
chemical_list: D012333:RNA, Messenger; D011994:Recombinant Proteins; D014280:Triglycerides; D002244:Carbon; D051048:Diacylglycerol O-Acyltransferase; D002950:Citrate (si)-Synthase; D010711:Phosphatidate Phosphatase; D009584:Nitrogen