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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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Project description:Oleaginous microorganisms have considerable potential for biofuel and commodity chemical production. Under nitrogen-limitation, Rhodococcus jostii RHA1 grown on benzoate, an analog of lignin depolymerization products, accumulated triacylglycerols (TAGs) to 55% of its dry weight during transition to stationary phase, with the predominant fatty acids being C16:0 and C17:0. Transcriptomic analyses of RHA1 grown under conditions of N-limitation and N-excess revealed 1,826 dysregulated genes. Genes whose transcripts were more abundant under N-limitation included those involved in ammonium assimilation, benzoate catabolism, fatty acid biosynthesis and the methylmalonyl-CoA pathway. Of the 16 atf genes potentially encoding diacylglycerol O-acyltransferases, atf8 transcripts were the most abundant during N-limitation (~50-fold more abundant than during N-excess). Consistent with Atf8 being a physiological determinant of TAG accumulation, a Δatf8 mutant accumulated 70% less TAG than wild-type RHA1 while atf8 overexpression increased TAG accumulation 20%. Genes encoding type-2 phosphatidic acid phosphatases were not significantly expressed. By contrast, three genes potentially encoding phosphatases of the haloacid dehalogenase superfamily and that cluster with, or are fused with other Kennedy pathway genes were dysregulated. Overall, these findings advance our understanding of TAG metabolism in mycolic acid-containing bacteria and provide a framework to engineer strains for increased TAG production.

2016-05-06 | GSE77158 | GEO

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.

Project description:Gene disruption of KTR9_0186 resulted in a 2-fold increase in TAG content in nitrogen starved cells. Lipase mutants subjected to carbon starvation, following nitrogen starvation, retained 75% more TAGs and retained pigmentation. Transcriptome expression data confirmed the deletion of KTR9_0186 and identified the up-regulation of key genes involved in fatty acid degradation, a likely compensatory mechanism for reduced TAG mobilization. The Gordonia sp. KTR9 strain used in this study has been previously described (PMID 16332812)

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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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Whole cell response to nitrogen deprivation in the diatom Phaeodactylum tricornutum

Project description:We combined transcriptional and metabolite analyses to monitor the effect of N deficiency at different molecular levels in order to get better insight on the acclimation strategies P. tricornutum employs under nitrogen limitation. Physiological data like neutral lipid measurement, cell growth and other cell chemistry measurements further complemented our molecular data. We showed that P. tricornutum is able to remobilize nitrogen through catabolism of various internal nitrogen-containing resources such as amino acids and proteins. N starvation was also accompanied by reduction in pigment pools as well as photosynthetic capacity. The global expression data showed that majority of metabolic changes were related to carbon and lipid metabolism. Decreased levels of carbon skeletons due to suppression of the Calvin cycle was compensated by breakdown of chrysolaminaran leading to up-regulation of OPPP, glycolysis, pyruvate metabolism and TCA cycle. These pathways provide precursors for fatty acid biosynthesis. In addition, remodeling of membrane lipids and up-regulation of the de novo TAG biosynthetic pathway was further supported by physiological measurements of neutral lipids, indicating TAG accumulation under N limitation. Our study gives a detailed image of adaptation of P. tricornutum to N starvation, and can be used for future metabolic manipulations to increase TAG production.

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DGAT enzymes are required for triacylglycerol synthesis and lipid droplets in adipocytes

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Transcript profiles of developing Arabidopsis dgat1-1 mutant seed

Project description:Global transcript profiling of Arabidopsis dgat1-1 seed at different stages of embryo development was used to identify differentially expressed genes in the mutant compared to wild-type (Col-0) seed. These genes provided information about the remodeling of lipid metabolism and TAG synthesis in response to the lack of DGAT1 activity.

2019-08-20 | GSE123303 | GEO

DGAT enzymes are required for triacylglycerol synthesis and lipid droplets in adipocytes

Project description:Murine embryonic fibroblasts were isolated from WT and DGAT1,DGAT2-KO (D1D2KO) animals. mRNA was isolated from cells untreated (UNDIFF) or treated (DIFF) according to standard differentiation protocol for adipocytes (Harris, C, et al. JLR 2011). 12 Samples total: 3 biological replicates of 3 undifferentiated wild type and D1D2KO mice and 3 biological replicates of 3 differentiated wild type and D1D2KO mice.

2011-01-31 | E-GEOD-26624 | biostudies-arrayexpress

DGAT1 phosphoproteome and long-term proteome

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

Time-resolved transcriptome analysis under sulfur starvation stress in the green microalga Chromochloris zofingiensis

Project description:Chromochloris zofingiensis has been proposed as a potential producer of lipids and the high-value carotenoid astaxanthin. Previous studies have demonstrated that TAG (triacylglycerol) and astaxanthin accumulated in a well-coordinated manner in response to different stresses in C. zofingiensis. The integrated production of lipids with co-products emerges as a new research direction and is proposed to be a promising approach toward offsetting the algal biodiesel production cost. Therefore, it is suggested C. zofingiensis can serve as research models for the integrated production. Sulfur starvation stress simultaneously induced TAG and astaxanthin accumulation in C. zofingiensis. To understand the mechanism underlying TAG and astaxanthin accumulation induced by sulfur starvation stress, we applied time-resolved high-throughput mRNA sequencing in C. zofingiensis.

2020-07-27 | GSE130454 | GEO

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