Dynamic metabolic profiling together with transcription analysis reveals salinity-induced starch-to-lipid biosynthesis in alga Chlamydomonas sp. JSC4

Abstract

Biodiesel production using microalgae would play a pivotal role in satisfying future global energy demands. Understanding of lipid metabolism in microalgae is important to isolate oleaginous strain capable of overproducing lipids. It has been reported that reducing starch biosynthesis can enhance lipid accumulation. However, the metabolic mechanism controlling carbon partitioning from starch to lipids in microalgae remains unclear, thus complicating the genetic engineering of algal strains. We here used “dynamic” metabolic profiling and essential transcription analysis of the oleaginous green alga Chlamydomonas sp. JSC4 for the first time to demonstrate the switching mechanisms from starch to lipid synthesis using salinity as a regulator, and identified the metabolic rate-limiting step for enhancing lipid accumulation (e.g., pyruvate-to-acetyl-CoA). These results, showing salinity-induced starch-to-lipid biosynthesis, will help increase our understanding of dynamic carbon partitioning in oleaginous microalgae. Moreover, we successfully determined the changes of several key lipid-synthesis-related genes (e.g., acetyl-CoA carboxylase, pyruvate decarboxylase, acetaldehyde dehydrogenase, acetyl-CoA synthetase and pyruvate ferredoxin oxidoreductase) and starch-degradation related genes (e.g., starch phosphorylases), which could provide a breakthrough in the marine microalgal production of biodiesel.

Novel insights into salinity-induced lipogenesis and carotenogenesis in the oleaginous astaxanthin-producing alga Chromochloris zofingiensis: a multi-omics study

“…In response to salt stress, all subunits of the chloroplastic ACCase were considerably up-regulated (over eightfold), suggesting that the chloroplastic ACCase represents a committed enzyme controlling the biosynthesis of fatty acids in C. zofingiensis. The salt-induced expression of ACCase has also been reported in some other algae including Chlamydomonas [26,39,40], Chlorella [41], and Nitzschia [42]. Obviously, in C. zofingiensis the transcriptional expression of ACCase subunits correlated well with each other (Additional file 8: Data S6), supporting their coordinated regulation as stated by previous reports [43,44].…”

“…Different algae have different salt tolerance capacities [9,28,39,40]. Here were found that C. zofingiensis could tolerate NaCl up to 0.2 mM; further increase of salt concentration, however, nearly blocked the cell growth (Fig.…”

“…Seemingly, starch serves as a temporary carbon sink and is transformed to TAG for long storage, which has been observed in several algae under ND conditions [15,89,100]. It has also been reported that salt stress triggered TAG accumulation at the expense of starch in algae [26,35,39,101], but the underlying mechanism remains rarely touched. We found in C. zofingiensis that coordinated up-regulation of multiple biological pathways contributed to the transition of starch to TAG upon salt stress, which are discussed as following.…”

A Data-Independent-Acquisition-based proteomic approach towards understanding the acclimation strategy of Microchloropsis gaditana CCMP526 in hypersaline conditions

“…Lipid accumulation was enhanced to 59.4% in Chlamydomonas sp. JSC4 by gradually increasing the salinity levels up to 2% (w/v) of sea salt (Ho et al, 2017). Accumulation of lipid or glycerol in such conditions involves a major metabolic shift in re-directing the carbon flux, which causes alteration in the abundance of proteins/enzymes involved in the metabolism of lipid or glycerol.…”

PhytoNet: Comparative co-expression network analyses across phytoplankton and land plants

“…http://dx.doi.org/10.1101/255067 doi: bioRxiv preprint first posted online Jan. 28, 2018; physiological changes in Chlamydomonas caused by abiotic stresses (35)(36)(37). Consequently, we decided to explore cluster 72 (http://aranet.mpimp-golm.mpg.de/responder.py?name=gene!cre!c72), which showed significant enrichment for the MapMan bin "stress" ( Figure 1B).…”