Genome-wide analysis of gene expression in Lobosphaera incisa under nitrogen starvation and different light intensities
Ontology highlight
ABSTRACT:
ORGANISM(S): Lobosphaera incisa
PROVIDER: GSE94666 | GEO | 2017/05/01
REPOSITORIES: GEO
Similar Datasets
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.
2018-10-11 | GSE104807 | GEO
Project description:Background: Microalgae are promising feedstocks for production of renewable biofuels and value-added bioproducts. Temperature and nitrogen supply are important environmental and nutritional factors affecting the growth and metabolism of microalgae, respectively. In this study, the growth and lipid accumulation of filamentous microalga Xanthonema hormidioides under different temperatures (5, 7, 10, 15, 20, 25, 27 and 30℃) and initial nitrogen concentrations (3, 9, 18 mM) were investigated, and its adaptive mechanisms of tolerance to low temperature and nitrogen stress were analysis by proteomics. Results: The optimum temperature range for the growth of X. hormidioides was between 15℃ and 20℃, and the algal cells had slow growth rate at 5℃ and could not survive at 30℃. The maximum biomass concentration was 11.73 g L-1 under the temperature of 20℃, and the highest total lipid content was 56.63% of dry weight. Low temperature did not change the fatty acids profiles but promoted the accumulation of unsaturated fatty acids of X. hormidioides. The maximum contents of palmitoleic acid, eicosapentaenoic acid and total fatty acid were 23.64%, 2.49% and 41.14% of dry weight, respectively. Proteomics was performed under three temperature (7、15、25℃), two nitrogen concentrations (3 and 18 mM) and two cultivation times (day3 and 12). A total of 6503 proteins were identified. In the low temperature, photosynthesis related proteins were down-regulation to protect the photosynthetic apparatus. The up-regulation of key enzymes DGAT and PDAT demonstrated the accumulation of TAGs under low nitrogen treatment. The proteins related to ribosome, phosphatidylinositol signaling system, antioxidant system and cold shock proteins (CSPs) in X. hormidioides were co-up-regulate under the treatment of low temperature, which can alleviate the damages induced by temperature stress and maintain the normal growth and metabolism of algal cells. Conclusions: X. hormidioides is a psychrotolerant microalga. It is an oleaginous filamentous microalga containing hyper palmitoleic acid and a certain amount of eicosapentaenoic acid with great potential for biofuel development, as well as for applications in nutritional health products and other industries.
2023-03-11 | PXD037434 | Pride
Project description:Thraustochytrids of the genera Schizochytrium and Aurantiochytrium accumulate oils rich in the essential, marine n3 fatty acid docosahexaenoic acid (DHA). DHA production in Aurantiochytrium sp T66 was studied with the aim to provide more knowledge about factors that affect the DHA-productivities and the contributions of the two enzyme systems used for fatty acid synthesis in thraustochytrids, fatty acid synthetase (FAS) and PUFA-synthase. Fermentations with nitrogen starvation, which is well-known to initiate lipid accumulation in oleaginous organisms, were compared to fermentations with nitrogen in excess where lipid accumulation was obtained by oxygen limitation. The specific productivities of fatty acids originating from FAS were considerably higher under nitrogen starvation than with nitrogen in excess, while the specific productivities of DHA were the same at both conditions. Global transcriptome analysis showed significant up-regulation of FAS under N-deficient conditions, while the PUFA-synthase genes were only marginally upregulated. Neither of them was upregulated under O2-limitation where nitrogen was in excess, suggesting that N-starvation mainly affects the FAS and may be less important for the PUFA-synthase. The transcriptome analysis also revealed responses likely to be related to the generation of reducing power (NADPH) for fatty acid synthesis.
2019-12-19 | GSE134374 | GEO
Project description:For the first time in Lactococcus lactis, amino acid starvation response was characterized. The natural imposition of isoleucine starvation, by its consumption during growth, associated to transcript profiling, allowed defining exhaustively this stress stimulon. It consisted of a general induction of nitrogen metabolism (amino acid biosynthesis and transport, proteolytic system and proteases), a strong repression of genes encoding major physiological activities (translation, transcription, carbon metabolism, purine and pyrimidine biosynthesis and fatty acid metabolism) and the induction of unexpected cross responses to acid, osmotic and oxidative stresses. Keywords: stress response, time course
2008-02-23 | GSE4872 | GEO
Project description:Fatty acid synthesis is closely linked to nutrient availability and cellular energetic status. The committed step in fatty acid synthesis is the acetyl CoA carboxylase. Eukaryotes have two genes encoding acetyl CoA carboxylases, one encoding a cytosolic enzyme and another coding for a mitochondrial enzyme. They catalyze the synthesis of malonyl CoA in the cytosol and the mitochondria, respectively. While cytosolic malonyl CoA is the precursor for fatty acid synthesis, mitochondrial malonyl CoA controls the transfer of fatty acyl group into the mitochondria by inhibiting carnitine/palmitoyl transferase activity and thus, regulates β-oxidation. In Saccharomyces cerevisiae, β-oxidation is restricted to the peroxisomes, raising the question of the function of the mitochondrial isoform (HFA1). In this study, we replaced the cytosolic Acc1 with Hfa1 expressed in the cytosol by removing the mitochondrial leader peptide, under control of the HFA1 promoter. We studied fatty acid synthesis and transcription profiles in this strain during starvation for carbon or nitrogen, using glucose or ethanol as the carbon source. Under all the conditions studied, the key sensor of energetic status, Snf1, was activated, indicating active inhibition of fatty acid synthesis. The pool size of fatty acids was smaller when Acc1 was replaced with truncated Hfa1 for fatty acid synthesis. Yet, the transcription profiles were similar in both the cases. These results point towards the conclusion that Hfa1 is either catalytically less efficient or it is more sensitive to inhibition by Snf1. Gene expression from a strain of Saccharomyces cerevisiae where cytosolic fatty acid synthesis occurs by mitochondrial acetyl CoA carboxylase (without its mitochondrial leader peptide) is compared with that in a reference strain while growing in chemostats on carbon or nitrogen starvation using glucose or ethanol as the carbon source. There are two strains (reference or mutant), two carbon sources (glucose or ethanol) and two limitations (carbon or nitrogen), resulting in 8 comparisons. Each array was performed in duplicate, resulting in 16 CEL files. Growth was limited by either carbon or nitrogen. When carbon was the limited nutrient, we tested growth on either glucose or ethanol (both using ammonium sulfate as the nitrogen source). When ammonium sulfate was limiting, we used either glucose or ethanol as the carbon source.
2010-06-08 | E-GEOD-21988 | biostudies-arrayexpress
Project description:For the first time in Lactococcus lactis, amino acid starvation response was characterized. The natural imposition of isoleucine starvation, by its consumption during growth, associated to transcript profiling, allowed defining exhaustively this stress stimulon. It consisted of a general induction of nitrogen metabolism (amino acid biosynthesis and transport, proteolytic system and proteases), a strong repression of genes encoding major physiological activities (translation, transcription, carbon metabolism, purine and pyrimidine biosynthesis and fatty acid metabolism) and the induction of unexpected cross responses to acid, osmotic and oxidative stresses. Keywords: stress response, time course Isoleucine starvation was imposed by the consumption of this amino acid during the growth of Lactococcus lactis IL1403 on ILV0.1 medium (CDM with ten-fold reduced concentrations of isoleucine, leucine and valine) and under controlled conditions (30 °C, pH 6.6, nitrogen atmosphere). Cell samples were harvested in exponential phase and after 30 min, 1.7 h and 3.5 h of isoleucine starvation. Total RNA was extracted from these samples and radiolabelled cDNA were prepared and hybridized on nylon arrays. 2053 amplicons specific of Lactococcus lactis IL1403 genes were spotted twice on the array. The 4 time-points were analyzed simultaneously and 3 independent repetitions were performed.
2010-06-25 | E-GEOD-4872 | biostudies-arrayexpress
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)
2015-02-14 | GSE60245 | GEO
Project description:Rheb, a ras-like small GTPase conserved from human to yeast, controls Tor kinase and plays a central role in regulation of cell growth depending on extracellular conditions. Fission yeast Rheb regulates amino acid uptake as well as response to nitrogen starvation. In this study we generated two mutants of Rheb, rhb1-DA4 and rhb1-DA8, and characterized them genetically. V17A mutation within the G1 box defined for the ras-like GTPases was responsible for rhb1-DA4, and Q52R I76F within the switch II domain for rhb1-DA8. In fission yeast, two events, induction of a meiosis initiating gene mei2+ and cell division without cell growth, are a typical response to nitrogen starvation. Under nitrogen-rich conditions, Rheb stimulates Tor kinase, which, in turn, suppresses the response to nitrogen starvation. While amino acid uptake was prevented by both rhb1-DA4 and rhb1-DA8 in a dominant fashion, the response to nitrogen starvation was prevented only by rhb1-DA4. rhb1-DA8 thereby allowed genetic dissection of the Rheb-dependent signaling cascade. We postulate that Rheb in fission may have two downstream elements, Tor kinase for regulation of the response to nitrogen starvation and the other element for regulation of amino acid uptake.
2009-09-29 | GSE14626 | GEO
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) A 12 x 135K array study using total RNA recovered from triplicate cultures of KTR9 under carbon starvation and triplicate cultures of KTR9 0186 Mutant under carbon starvation.
2015-02-14 | E-GEOD-60245 | biostudies-arrayexpress
Project description:Rheb, a ras-like small GTPase conserved from human to yeast, controls Tor kinase and plays a central role in regulation of cell growth depending on extracellular conditions. Fission yeast Rheb regulates amino acid uptake as well as response to nitrogen starvation. In this study we generated two mutants of Rheb, rhb1-DA4 and rhb1-DA8, and characterized them genetically. V17A mutation within the G1 box defined for the ras-like GTPases was responsible for rhb1-DA4, and Q52R I76F within the switch II domain for rhb1-DA8. In fission yeast, two events, induction of a meiosis initiating gene mei2+ and cell division without cell growth, are a typical response to nitrogen starvation. Under nitrogen-rich conditions, Rheb stimulates Tor kinase, which, in turn, suppresses the response to nitrogen starvation. While amino acid uptake was prevented by both rhb1-DA4 and rhb1-DA8 in a dominant fashion, the response to nitrogen starvation was prevented only by rhb1-DA4. rhb1-DA8 thereby allowed genetic dissection of the Rheb-dependent signaling cascade. We postulate that Rheb in fission may have two downstream elements, Tor kinase for regulation of the response to nitrogen starvation and the other element for regulation of amino acid uptake. Gene expression profile under nitrogen starvation in fission yeast. Type of experiment: Comparing between vegetatively-growing control cells and cells 3 hrs after nitrogen starvation. Experimental factor: Gene expression profile after nitrogen starvation in the rhb1-D4 or rhb1-D8 cells. Quality control steps taken: All experiments were repeated more than twice except for the tsc2D which was previously reported. Keywards: Nitrogen starvation, rhb1-D4, rhb1-D8
2009-09-28 | E-GEOD-14626 | biostudies-arrayexpress