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Open Access Research

Molecular and cellular mechanisms of neutral lipid accumulation in diatom following nitrogen deprivation

Zhi-Kai Yang1, Ying-Fang Niu1, Yu-Han Ma1, Jiao Xue1, Meng-Han Zhang1, Wei-Dong Yang1, Jie-Sheng Liu1, Song-Hui Lu1, Yuanfang Guan2* and Hong-Ye Li1*

Author Affiliations

1 Key Laboratory of Eutrophication and Prevention of Red Tide of Guangdong Higher Education Institute, College of Life Science, Jinan University, Guangzhou, 510632, China

2 Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan, 48109, United States of America

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Biotechnology for Biofuels 2013, 6:67  doi:10.1186/1754-6834-6-67

Published: 4 May 2013

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.

Keywords:
Microalga; Nitrogen deprivation; Lipid; Membrane remodeling; Transcriptomics