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Three acyltransferases and a nitrogen responsive regulator are implicated in nitrogen starvation-induced triacylglycerol accumulation in Chlamydomonas

ABSTRACT: Three acyltransferases, DGAT1, DGTT1, and PDAT1, are induced by nitrogen starvation and are likely to have a role in TAG accumulation based on their patterns of expression. Each gene also shows increased mRNA abundance in other TAG-accumulating conditions (-S, -P, -Zn, -Fe). Insertional mutants, pdat1-1 and pdat1-2, accumulate 25% less TAG compared to the parent strain, D66+, which demonstrates the relevance of the trans-acylation pathway in Chlamydomonas. The biochemical functions of DGTT1 and PDAT1 were validated by rescue of oleic acid sensitivity and restoration of TAG accumulation in a yeast strain lacking all acyltransferase activity. Time course analysis suggest than an SBP domain transcription factor protein, whose mRNA increases precede that of other genes like DGAT1, is a candidate regulator of the N-deficiency response. An insertional mutant, nrr1-1, accumulates only 50% of the TAG compared to the parental strain in N-starvation conditions and is unaffected by other nutrient stresses, suggesting the operation of multiple signaling pathways leading to stress-induced TAG accumulation.

ORGANISM(S): Chlamydomonas reinhardtii

PROVIDER: GSE34585 | GEO | 2013/01/10

SECONDARY ACCESSION(S): PRJNA150503

REPOSITORIES: GEO

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Three acyltransferases and a nitrogen responsive regulator are implicated in nitrogen starvation-induced triacylglycerol accumulation in Chlamydomonas

Project description:Three acyltransferases, DGAT1, DGTT1, and PDAT1, are induced by nitrogen starvation and are likely to have a role in TAG accumulation based on their patterns of expression. Each gene also shows increased mRNA abundance in other TAG-accumulating conditions (-S, -P, -Zn, -Fe). Insertional mutants, pdat1-1 and pdat1-2, accumulate 25% less TAG compared to the parent strain, D66+, which demonstrates the relevance of the trans-acylation pathway in Chlamydomonas. The biochemical functions of DGTT1 and PDAT1 were validated by rescue of oleic acid sensitivity and restoration of TAG accumulation in a yeast strain lacking all acyltransferase activity. Time course analysis suggest than an SBP domain transcription factor protein, whose mRNA increases precede that of other genes like DGAT1, is a candidate regulator of the N-deficiency response. An insertional mutant, nrr1-1, accumulates only 50% of the TAG compared to the parental strain in N-starvation conditions and is unaffected by other nutrient stresses, suggesting the operation of multiple signaling pathways leading to stress-induced TAG accumulation. Sampling of Chlamydomonas 2137 cultivated in TAP, N-Free TAP or TAP with varying amounts of N.

2013-01-10 | E-GEOD-34585 | biostudies-arrayexpress

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The effects of putative lipase and wax ester synthase/acyl-CoA:diacylglycerol acyltransferase gene knockouts on triacylglycerol accumulation and transcriptome expression in Gordonia sp. KTR9.

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Project description:Enhanced fatty acid (FA) synthesis and uptake underpin the sustained membrane biogenesis and ATP production required for melanoma cell growth and division1-4. However, to thrive, melanoma cells must avoid a potential reduction in cell growth signalling, rampant reactive oxygen species (ROS) generation, and the build-up of toxic lipid species that can accompany excess free FA5. Here, we uncover and address the significance of frequent amplification and up-regulation of the Diacylglycerol O-acyltransferase 1 (DGAT1) gene in melanoma, whose encoded product catalyses the final step of Triacyglyceride (TAG) synthesis. Consistent with the classification of DGAT1 as an oncogene, we found that forced DGAT1 expression in p53 mutant zebrafish melanocytes was sufficient to induce melanoma, and accelerated melanoma progression initiated by co-expression of oncogenic BRAF or NRAS. Regarding DGAT1 function in human melanoma cells, its depletion, or alternatively pharmacological inhibition, suppressed mTOR-S6K signalling and increased levels of acyl carnitine species— FA derivatives that are the limiting substrate for FA oxidation (FAO). In turn, increased FAO induced mitochondrial malfunction, ROS generation, and lipid peroxidation. However, the resultant oxidative stress induced NRF2 and SESTRIN2 (SESN2) expression, which limited the extent of cell death. Conversely, DGAT1 over-expression enhanced mTOR-S6K signalling and cell growth, and protected against ROS, particularly in hypoxic conditions. Together, our data establish DGAT1 as a bona fide oncogene essential in melanoma cells for enabling FA accumulation.

2023-03-10 | PXD017487 | Pride

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Project description: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.

2019-07-22 | PXD012391 | JPOST Repository

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