title: Molecular and cellular mechanisms of neutral lipid accumulation in diatom following nitrogen deprivation.
abstract: BACKGROUND
  Nitrogen limitation can induce neutral lipid accumulation in microalgae, as well as inhibiting their growth. Therefore, to obtain cultures with both high biomass and high lipid contents, and explore the lipid accumulation mechanisms, we implemented nitrogen deprivation in a model diatom Phaeodactylum tricornutum at late exponential phase.
  
  
  RESULTS
  Neutral lipid contents per cell subsequently increased 2.4-fold, both the number and total volume of oil bodies increased markedly, and cell density rose slightly. Transcriptional profile analyzed by RNA-Seq showed that expression levels of 1213 genes (including key carbon fixation, TCA cycle, glycerolipid metabolism and nitrogen assimilation genes) increased, with a false discovery rate cut-off of 0.001, under N deprivation. However, most light harvesting complex genes were down-regulated, extensive degradation of chloroplast membranes was observed under an electron microscope, and photosynthetic efficiency declined. Further identification of lipid classes showed that levels of MGDG and DGDG, the main lipid components of chloroplast membranes, dramatically decreased and triacylglycerol (TAG) levels significantly rose, indicating that intracellular membrane remodeling substantially contributed to the neutral lipid accumulation.
  
  
  CONCLUSIONS
  Our findings shed light on the molecular mechanisms of neutral lipid accumulation and the key genes involved in lipid metabolism in diatoms. They also provide indications of possible strategies for improving microalgal biodiesel production.
authors: Key Laboratory of Eutrophication and Prevention of Red Tide of Guangdong Higher Education Institute, College of Life Science, Jinan University, Guangzhou, 510632, China. gyuanfan@umich.edu.
authors: Zhi-Kai
authors: ZK
authors: Yang
authors: Ying-Fang
authors: YF
authors: Niu
authors: Yu-Han
authors: YH
authors: Ma
authors: Jiao
authors: J
authors: Xue
authors: Meng-Han
authors: MH
authors: Zhang
authors: Wei-Dong
authors: WD
authors: Yang
authors: Jie-Sheng
authors: JS
authors: Liu
authors: Song-Hui
authors: SH
authors: Lu
authors: Yuanfang
authors: Y
authors: Guan
authors: Hong-Ye
authors: HY
authors: Li
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