Nannochloropsis metabolism during transition from quiescence to autotrophy.
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PROVIDER: PRJNA530583 | ENA |
REPOSITORIES: ENA
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Project description:Purpose: The marine microalgae Nannochloropsis oceanica (CCMP1779) is a prolific producer of oil and is considered a viable and sustainable resource for biofuel feedstocks. Nitrogen (N) availability has a strong impact on the physiological status and metabolism of microalgal cells. However the exact nature of this response is poorly understood. To fill this gap we performed transcriptomic profiling combined with cellular and molecular analyses of N. oceanica CCMP1779 during the transition from quiescence to autotrophy. Methods: Nannochloropsis cells (50 ml per sample) were harvested for RNA isolation during nitrogen deprivation (N-) and after nitrogen resupply (NR) at the following time points: 6, 12, 24, 48 and 72 h. For each time point two biological replicates were harvested. RNA was extracted using the E.Z.N.A® Plant RNA kit (OMEGA) according to the manufacturer’s instructions. RNA quality was verified using the Bioanalyzer (Agilent). Single-end, 50 bp nucleotide sequences were acquired for each sample using an Illumina HiSeq 2500 (MSU-Research Technology Support Facility). RNA-Seq reads were trimmed using Trimmomatic (v0.32) with removal of leading and trailing low quality bases (below quality score 10 with a 4-base wide sliding window) as well as TruSeq Single End adaptors. The resulting reads were aligned to the N. oceanica CCMP1779 genome assembly (GSE36959) using STAR (2.3.0e) (Dobin et al., 2013) by only allowing unique mapping, a maximum of 4 mismatches per pair and a maximum intron length of 10,000 bp. The HTSeq (0.6.1) was used to generate a count table for all genes using the exon as the feature type as well as the intersect-nonempty mode so that only reads that were completely aligned to two genes are considered ambiguous. HTSeq count tables were used for differential expression analysis using DEseq2. Differential gene expression was examined using DESeq2. A generalized linear model was fit, and we tested on condition (deprivation or recovery) and the time:condition interaction with log2-fold changes greater than 1. Significant differentially expressed genes with p-values less than 0.01 were identified after Benjamini-Hochberg (BH) multiple testing correction. Differentially expressed genes were clustered based on expression using K-means clustering (k = 4) with the Pearsons correlation distance metric within MeV (4.8.1). Results: We showed that N deprivation-induced quiescence is accompanied by a strong reorganization of the photosynthetic apparatus and changes in the lipid homeostasis leading to accumulation of triacylglycerol (TAG). Cell cycle activation and re-establishment of photosynthetic activity observed in response to resupply of the growth medium with N were accompanied by a rapid degradation of TAG stored in lipid droplets (LDs). Beside observing LD translocation into vacuoles we also provide evidence for direct interaction between the lipid droplet surface protein (NoLDSP) and autophagy-related 8 (NoATG8) protein and show a role of microlipophagy in LD turnover in N. oceanica CCMP1779. Conclusions: This knowledge is crucial not only for understanding the fundamental mechanisms controlling the cellular energy homeostasis in microalgal cells but also for the development of efficient strategies to achieve higher algal biomass and better microalgal lipid productivity.
2019-10-01 | GSE129245 | GEO
Project description:To identify proteins of Saccharomyces cerevisiae involved in the transition to quiescence in minimal buffered media, we compared the proteome of cells from exponential phase and a few hours after glucose-depletion.
2023-12-13 | PXD041191 | Pride
Project description:Nannochloropsis oceanica CCMP1779 is a marine unicellular stramenopile and an emerging reference species for basic research on oleogenic microalgae with biotechnological relevance. We investigated its physiology and transcriptome under light/dark cycles. We observed oscillations in lipid content and a predominance of cell division in the first half of the dark phase. Globally, more than 60% of the genes cycled in N. oceanica CCMP1779, with gene expression peaking at different times of the day. Interestingly, the phase of expression of genes involved in certain biological processes was conserved across photosynthetic lineages. Furthermore, in agreement with our physiological studies we found the processes of lipid metabolism and cell division enriched in cycling genes. For example, there was tight coordination of genes involved in the lower part of glycolysis, fatty acid synthesis and lipid production at dawn preceding lipid accumulation during the day. Our results suggest that diel lipid storage plays a key role for N. oceanica CCMP1779 growth under natural conditions making this alga a promising model to gain a basic mechanistic understanding of triacylglycerol production in photosynthetic cells. Our data will help the formulation of new hypotheses on the regulation transcriptional control of cell growth and metabolism in Nannochloropsis. Nannochloropsis oceanica CCMP was entrained to 12:12 light:dark cycles and biological replicates collected every 3 hours for a cycle for a total of 16 samples.
2015-08-01 | E-GEOD-69460 | biostudies-arrayexpress
Project description:Unicellular marine algae have promise for providing sustainable and scalable biofuel feedstocks, although no single species has emerged as a preferred organism. Moreover, adequate molecular and genetic resources prerequisite for the rational engineering of marine algal feedstocks are lacking for most candidate species. Heterokonts of the genus Nannochloropsis naturally have high cellular oil content and are already in use for industrial production of high value lipid products. First success in applying reverse genetics makes Nannochloropsis species attractive models to investigate the cell and molecular biology and biochemistry of this fascinating organism group. (Principle findings) Here we present the assembly of the 28.7 Mb genome of Nannochloropsis oceanica CCMP1779. RNA sequencing data from N-replete and N-depleted growth conditions support a total of 11,973 genes, which in addition to automatic annotation were manually inspected to predict the biochemical repertoire for this organism. Among others, more than 100 genes putatively related to lipid metabolism, 114 predicted transcription factors and 109 transcriptional regulators were annotated. In addition, we provide protocols for the transformation of the sequenced strain. (Significance) The availability of genomic and transcriptomic data for Nannochloropsis oceanica CCMP1779, along with efficient transformation protocols provides a blueprint for future detailed gene functional analysis and phylogenetic comparison of Nannochloropsis species by a growing academic community focused on this genus. one sample each of nitrogen-replete and nitrogen-depleted conditions
2012-04-04 | E-GEOD-36959 | biostudies-arrayexpress
Project description:Transcriptional regulation in response to nitrogen stress for one ant two days, and epigenome-association with phenotypic plasticity of lipid metabolism are uncovered in marine microalga Nannochloropsis oceanica IMET1.
2023-08-23 | GSE225079 | GEO
Project description:Cells switch between quiescence and proliferation states for maintaining tissue homeostasis and regeneration. At the restriction point (R-point), cells become irreversibly committed to the completion of the cell cycle independent of mitogen. The mechanism involving hyper-phosphorylation of retinoblastoma (Rb) and activation of transcription factor E2F is linked to the R-point passage. However, stress stimuli trigger exit from the cell cycle back to the mitogen-sensitive quiescent state after Rb hyper-phosphorylation but only until APC/CCdh1 inactivation. In this study, we developed a mathematical model to investigate the reversible transition between quiescence and proliferation in mammalian cells with respect to mitogen and stress signals. The model integrates the current mechanistic knowledge and accounts for the recent experimental observations with cells exiting quiescence and proliferating cells. We show that Cyclin E:Cdk2 couples Rb-E2F and APC/CCdh1 bistable switches and temporally segregates the R-point and the G1/S transition. A redox-dependent mutual antagonism between APC/CCdh1 and its inhibitor Emi1 makes the inactivation of APC/CCdh1 bistable. We show that the levels of Cdk inhibitor (CKI) and mitogen control the reversible transition between quiescence and proliferation. Further, we propose that shifting of the mitogen-induced transcriptional program to G2-phase in proliferating cells might result in an intermediate Cdk2 activity at the mitotic exit and in the immediate inactivation of APC/CCdh1. Our study builds a coherent framework and generates hypotheses that can be further explored by experiments.
2020-06-22 | BIOMD0000000954 | BioModels
Project description:Reorganization of 3D chromatin structure in response to nitrogen stress for one ant two days, and epigenome-association with phenotypic plasticity of lipid metabolism are firstly uncovered in marine microalga Nannochloropsis oceanica IMET1.
2023-08-23 | GSE223130 | GEO
Project description:Limited systems-level understanding of oil synthesis in wild oleaginous algae has hindered the development of microalgal feedstock. Nannochloropsis is a small unicellular microalgae widely distributed in oceans and fresh water. In many large-scale and pilot-scale outdoor cultivation facilities, Nannochloropsis strains have been found to be capable of robust growth when supplied with flue gases, naturally accumulating large quantities of oils in a stationary phase, and exhibiting resistance to environmental contaminants. The rich genomic resources, compact genomes, resistance to foreign DNA invasion, wide ecological adaptation, large collections of natural strains and the demonstrated ability to grow on a large scale suggested Nannochloropsis can serve as research models and platform strains for economical and scalable photosynthetic production of fuels and chemicals. To untangle the intricate genome-wide networks underlying the robust biomass accumulation and oil production in Nannochloropsis, we applied high-throughput mRNA-sequencing and reconstructed the structure and dynamics of the genome-wide functional network underlying robust microalgal triacylglycerol (TAG) production in Nannochloropsis oceanica, by tracking the genome-wide, single-base-resolutiontranscript change for the complete time-courses of nitrogen-depletion-induced TAG synthesis. Nannochloropsis oceanica IMET1 cells were grown in liquid cultures under continuous light (approximately 50 M-BM-5mol photons m-2 s-1) at 25M-bM-^DM-^C and aerated by bubbling with a mixture of 1.5% CO2 in air. Mid-logarithmic phase algal cells were collected and washed three times with axenic seawater. Equal numbers of cells were re-inoculated in nitrogen replete medium (Control condition or C, i.e. N+) and nitrogen deprived medium (N deficiency or N, i.e. N-) with 50M-BM-5mol m-2 s-1 light intensity, respectively. Cell aliquots were collected for RNA isolation after being transferred to the designated conditions for 3h, 4h, 6h, 12h, 24h and 48h. Three biological replicates of algal cultures were established under each of the above M-bM-^@M-^\CM-bM-^@M-^] (i.e. N+) and M-bM-^@M-^\NM-bM-^@M-^] (i.e. N-) conditions, respectively. In total, 36 samples collected at six time points (3h,4h,6h,12h,24h and 48h) were used for mRNA-Seq library preparation and then submitted to Illumina HiSeq 2000 for sequencing.
2014-05-14 | E-GEOD-42508 | biostudies-arrayexpress
Project description:Unicellular marine algae have promise for providing sustainable and scalable biofuel feedstocks, although no single species has emerged as a preferred organism. Moreover, adequate molecular and genetic resources prerequisite for the rational engineering of marine algal feedstocks are lacking for most candidate species. Heterokonts of the genus Nannochloropsis naturally have high cellular oil content and are already in use for industrial production of high value lipid products. First success in applying reverse genetics makes Nannochloropsis species attractive models to investigate the cell and molecular biology and biochemistry of this fascinating organism group. (Principle findings) Here we present the assembly of the 28.7 Mb genome of Nannochloropsis oceanica CCMP1779. RNA sequencing data from N-replete and N-depleted growth conditions support a total of 11,973 genes, which in addition to automatic annotation were manually inspected to predict the biochemical repertoire for this organism. Among others, more than 100 genes putatively related to lipid metabolism, 114 predicted transcription factors and 109 transcriptional regulators were annotated. In addition, we provide protocols for the transformation of the sequenced strain. (Significance) The availability of genomic and transcriptomic data for Nannochloropsis oceanica CCMP1779, along with efficient transformation protocols provides a blueprint for future detailed gene functional analysis and phylogenetic comparison of Nannochloropsis species by a growing academic community focused on this genus.
2012-04-04 | GSE36959 | GEO
Project description:Regulating the transition of T lymphocytes from quiescence into an activated, proliferating state involves initiation of programmes that result in cell cycle entry (proliferation) and the growth cycle (blastogenesis). This study analyses the expression of mRNA regulsted during the transition from quiescence into the cell cycle. We used micro-arrays to monitor the dynamical behaviour of expression of genes expressed in primary human T cells stimulated with CD3/CD28
2012-01-01 | GSE32607 | GEO