Understanding lipid metabolism in high-lipid-producing Chlorella vulgaris mutants at the genome-wide level


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Sarayloo E., Tardu M., Unlu Y. S., Simsek S., Cevahir G., Erkey C., ...More

ALGAL RESEARCH-BIOMASS BIOFUELS AND BIOPRODUCTS, vol.28, pp.244-252, 2017 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 28
  • Publication Date: 2017
  • Doi Number: 10.1016/j.algal.2017.11.009
  • Journal Name: ALGAL RESEARCH-BIOMASS BIOFUELS AND BIOPRODUCTS
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.244-252
  • Keywords: Chlorella vulgaris, De novo RNA-seq, Biodiesel, Lipid biosynthesis, Mutagenesis, FATTY-ACID-COMPOSITION, SUPEROXIDE DISMUTASES, SIROHEME BIOSYNTHESIS, EPOXIDE HYDROLASES, RANDOM MUTAGENESIS, STRESS-RESPONSE, CELL-GROWTH, MICROALGAE, GENES, NANNOCHLOROPSIS
  • Istanbul University Affiliated: Yes

Abstract

In this study, physical and chemical mutagenesis methods were applied to enhance lipid productivity in Chlorella vulgaris. Then, de novo RNA-seq was performed to observe lipid metabolism changes at the genome-wide level. Characterization of two mutants, UV-715 and EMS-25, showed marked increases in lipid contents, i.e., 42% and 45%, respectively. In addition, the biomass productivity of the UV-715 cells was 9% higher than that of wildtype cells. Furthermore, gas chromatography-mass spectrophotometry analysis showed that both mutants have higher fatty acid methyl ester (FAME) contents than wild-type cells. To understand the effect of mutations that caused yield changes in UV-715 and EMS-25 cells at a genome-wide level, we carried out de novo RNA-seq. As expected, the transcriptional levels of the lipid biosynthesis genes were up-regulated, while the transcriptional levels of genes involved in lipid catabolism were down-regulated. Surprisingly, the transcriptional levels of the genes involved in nitrate assimilation and detoxification of reactive oxygen species (ROS) were significantly increased in the mutants. The genome-wide analysis results highlight the importance of nitrate metabolism and detoxification of ROS for high biomass and lipid productivity.