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RNA-Seq of Chromochloris zofingiensis in response to nitrogen deprivation

ABSTRACT: Chromochloris zofingiensis, featured by the capability of simultaneously synthesizing triacylglycerol (TAG) and astaxanthin, is emerging as a leading candidate alga for production uses. In order to better understand the oleaginous mechanism of this alga, we conducted a multi-omics analysis by systematically integrating the time-resolved transcriptomes, lipidomes, and metabolomes in response to nitrogen deprivation. The data analysis unraveled the distinct mechanism of TAG accumulation, which involved the coordinated stimulation of multiple biological processes including supply of energy and reductants, carbon reallocation from protein and starch, ‘pushing’ and ‘pulling’ carbon to TAG synthesis. Unlike in the model alga Chlamydomonas, the de novo fatty acid synthesis in C. zofingiensis was promoted, together with the enhanced turnover of both glycolipids and phospholipids, supporting the drastic need of acyls for TAG assembly. Moreover, genome-wide analysis identified many key functional enzymes and transcription factors with engineering potential for TAG modulation. Two genes encoding glycerol-3-phosphate acyltransferase (GPAT), the first committed enzyme for TAG assembly, were found in the genome of C. zofingiensis; in vivo functional characterization revealed that the extrachloroplastic GPAT instead of the chloroplastic one plays a central role in TAG synthesis. These findings illuminate distinct mechanism of oleaginousness of C. zofingiensis and pave a way toward rational manipulation of this alga as an emerging model for trait improvements.

ORGANISM(S): Chromochloris zofingiensis

PROVIDER: GSE113802 | GEO | 2019/07/31

REPOSITORIES: GEO

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Project description:Plants and microalgae have the ability to harness sunlight into energy dense molecules such as triacylglycerols (TAGs). TAGs hold great importance for human and animal nutrition, and are also a source for renewable energy. Acyl-CoA-dependent TAG synthesis by diacylglycerol acyltransferases (DGATs) in oilseeds has been well characterized, but how the ectopic introduction of TAG synthesis in vegetative tissues of plants affects metabolism is largely unknown. Here we report the identification and characterization of several Chlamydomonas reinhardtii Diacylglycerol Acyltransferase Type Two (DGTT) enzymes and their use in engineering TAG biosynthesis in plant vegetative tissues. Focusing on DGTT2 we demonstrate that it can accept a broad range of substrates. Production of DGTT2 in Arabidopsis results in distinct seedling phenotypes and accumulation of TAG with very long chain fatty acids (VLCFA), in both seedlings (23.4-fold increase) and in the leaves of soil-grown plants (13.3-fold increase). Levels of surface lipids, such as waxes and cutins, are decreased in DGTT2-producing lines, consistent with a decreased carbon/acyl flux to the surface lipid pathway. Global transcript analysis showed that very few genes had altered expression. Little to no change in the transcripts of wax/cutin pathway genes was observed in response to altered carbon partitioning into TAGs in the leaves suggesting that the supply of acyl groups for surface lipid biosynthesis is not transcriptionally adjusted in the transgenic lines. As an indication that the DGTT2-producing plants are richer in feed value, the generalist herbivore Spodoptera exigua reared on the transgenic plants gained more weight. Apparently, the substrate specificity of DGTT2 from Chlamydomonas when produced in the Arabidopsis cells leads to diversion of carbon from surface compounds in TAGs and enhances the nutritional value of leaves. 4 biological replicates DGTT2 transgenic plants are compared to 4 biological replicates of wild type

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RNA-Seq of Chromochloris zofingiensis in response to nitrogen deprivation

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