Dataset Information

Algal Protein Kinase, Triacylglycerol Accumulation Regulator1, Modulates Cell Viability and Gametogenesis in Carbon/Nitrogen Imbalanced Conditions

ABSTRACT: Nutrient-deprived microalgae accumulate triacylglycerol (TAG) in lipid droplets. A Dual-specificity tyrosine phosphorylation-regulated kinase, TAG-accumulation-regulator-1 (TAR1) has been shown to be required for acetate-dependent TAG accumulation and degradation of chlorophyll and photosynthesis-related proteins in photomixotrophic nitrogen (N)-deficient conditions (Kajikawa et al. 2015). However, this previous report only examined the particular condition. Here, we report that under photoautotrophic N-deficient conditions, tar1-1 cells, with a mutation in the TAR1 gene, accumulated higher levels of TAG and starch, and maintained higher levels of cell viability and lower levels of H2O2 generation compared to wild-type (WT) cells. Transcriptomic analyses suggest that genes involved in the scavenging of reactive oxygen species, such as APX1, GPX5, PTOX1, TRX7 are not repressed in tar1-1cells. In contrast, mating efficiency and mRNA levels for key regulators in gametogenesis, MID, MTD and FUS, were suppressed in tar1-1 cells. Among the 426 TAR1-dependent phosphoproteins detected by phosphoproteomic analysis, several protein kinases and enzymes related to N assimilation and carbon metabolism are of particular interest. Characterization of these putative downstream factors may elucidate the molecular pathway whereby TAR1 mediates cellular propagation and carbon- and nitrogen- metabolism under C/N imbalance stress conditions.

ORGANISM(S): Chlamydomonas

SUBMITTER: Hideya Fukuzawa

PROVIDER: PXD012391 | JPOST Repository | Mon Jul 22 00:00:00 BST 2019

REPOSITORIES: jPOST

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Publications

Algal Protein Kinase, Triacylglycerol Accumulation Regulator 1, Modulates Cell Viability and Gametogenesis in Carbon/Nitrogen-Imbalanced Conditions.

Shinkawa Haruka H Kajikawa Masataka M Nomura Yuko Y Ogura Mayu M Sawaragi Yuri Y Yamano Takashi T Nakagami Hirofumi H Sugiyama Naoyuki N Ishihama Yasushi Y Kanesaki Yu Y Yoshikawa Hirofumi H Fukuzawa Hideya H

Plant & cell physiology 20190401 4

Nutrient-deprived microalgae accumulate triacylglycerol (TAG) in lipid droplets. A dual-specificity tyrosine phosphorylation-regulated kinase, TAG accumulation regulator 1 (TAR1) has been shown to be required for acetate-dependent TAG accumulation and the degradation of chlorophyll and photosynthesis-related proteins in photomixotrophic nitrogen (N)-deficient conditions (Kajikawa etï¿½al. 2015). However, this previous report only examined particular condition. Here, we report that in photoautotr ...[more]

PMID: 30668822

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Project description:The oleaginous green microalga Neochloris oleoabundans accumulates both starch and lipids to high levels under stress conditions such as nitrogen starvation. In order to steer the metabolism towards starch or lipids only, it is important to understand the mechanisms behind it. In this study physiological changes and gene expression upon nitrogen starvation were analysed in controlled flat-panel photobioreactors over both short- and long-term time-scales. Starch accumulation is transient and occurs rapidly within 24 hrs upon starvation, while lipid accumulation lasts longer and reaches a maximum after 4 days. The major fraction of accumulated lipids is composed of de novo synthesized neutral lipids - triacylglycerides (TAG) - and is characterized by a decreased composition of the polyunsaturated fatty acids (PUFAs) C18:3 and C16:3 and an increased composition of the mono-unsaturated and saturated fatty acids C18:1/C16:1 and C18:0/C16:0, respectively. RNA-sequencing revealed that genes related to starch biosynthesis and degradation show different temporal expression dynamics compared to those of lipid biosynthesis. An immediate rapid increase in starch synthesis gene expression is followed by an increase in starch degradation and decrease in starch synthesis gene expression. In contrast, increased gene expression for fatty acid and TAG synthesis is initiated later and occurs more gradually. Expression of several fatty acid desaturase (FAD) genes was decreased upon starvation, which corresponds to the observed changes to higher levels of mono-unsaturated and saturated fatty acids. Moreover, several homologs of transcription regulators that were implicated in controlling starch and lipid metabolism in other microalgae showed differential gene expression and might be key regulators of starch and lipid metabolism in N. oleoabundans as well. Promising candidates for future metabolic engineering are a DYRKP homolog that in Chlamydomonas acts as a negative regulator of carbon storage and photosynthetic efficiency under N-starvation, and two bZIP-type regulators that have been implicated to control several steps in microalgal TAG synthesis. Our data for the first time show the temporal dynamics of storage compound accumulation and transcriptional changes on a short- and long-term time-scale during nitrogen starvation in N. oleoabundans, and increases insight into the genetic foundation for starch and lipid metabolism in this microalga. This information and the identified target genes can now be used for metabolic engineering strategies towards tailored N. oleoabundans strains for industrial applications with increased lipid production and altered fatty acid composition.

Dataset Information

Algal Protein Kinase, Triacylglycerol Accumulation Regulator1, Modulates Cell Viability and Gametogenesis in Carbon/Nitrogen Imbalanced Conditions

Publications

Algal Protein Kinase, Triacylglycerol Accumulation Regulator 1, Modulates Cell Viability and Gametogenesis in Carbon/Nitrogen-Imbalanced Conditions.

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