Time：Nov. 6, 2013  15:30   

Venue：Room 506, Museum for Aquatic Organisms 

Speaker：Han Danxiang    Arizona State University

Title：Mechanisms of oil production in Nannochloropsis: Insights from transcriptomics and lipidomics analysis

Brief Introduction:

To reveal mechanisms of oleaginousness in microalgae, the transcriptomic and lipidomic dynamics of the oleaginous microalga Nannochloropsis oceanica IMET1 grown under nitrogen-replete (N+) and N-depleted (N-) conditions were simultaneously tracked. At the transcriptional level, enhanced triacyglycerol (TAG) synthesis under N- conditions primarily involved the up-regulation of seven of 13 putative diacylglycerol acyltransferase (DGAT) genes, in concert with elevating the other Kennedy-pathway genes. Under N- conditions, despite down-regulation of most de novo fatty acid synthesis genes, the carbon flux shunting into glycerolipid synthesis from protein and carbohydrate metabolic pathways increased, resulting in increased overall TAG production. TAG accumulation was further augmented by up-regulation of genes supplying carbon precursors and energy for de novo fatty acid synthesis, including pyruvate dehydrogenase complex (PDHC), glycolysis, PDHC bypass, and suites of specific transporters. Moreover, citric acid cycle activity and beta-oxidation in mitochondria were greatly enhanced to utilize carbon skeletons derived from membrane lipids and proteins to form additional TAG. Comparing the transcriptional regulation with that of the non-oleaginous microalga Chlamydomonas reinhardtii revealed that oleaginousness may stem from N. oceanica’s ability to produce higher levels of carbon precursors and DGAT transcripts. This temporal molecular model of microalgal oleaginousness will enable more rational genetic engineering of TAG production.