Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

RNA-seq of Chlamydomonas reinhardtii response to nitrogen deprivation

ABSTRACT: Chlamydomonas reinhardtii forms lipid droplets rich in triacylglycerols when nutrient-deprived. To begin studying the mechanisms underlying this process, N-deprivation was used to induce triacylglycerol accumulation and changes in developmental programs such as gametogenesis. Comparative global analysis of transcripts under induced and non-induced conditions was applied as a first approach to study molecular changes that promote or accompany triacylglycerol accumulation in cells encountering a new nutrient environment. Towards this goal, high-throughput sequencing technology was employed to generate large numbers of expressed sequence tags of 8 biologically independent libraries (6 Illumina libraries, 2 454 libraries), four for each condition, N-replete and N-deprived, that allowed a statistically sound comparison of expression levels under the two tested conditions. Inferences on metabolism based on transcriptional analysis can only be indirect but were supported in parts by biochemical experiments. N-deprivation led to a marked redirection of metabolism as the carbon source acetate was no longer converted to cell building blocks by the glyoxylate cycle and gluconeogensis, but funneled directly into fatty acid biosynthesis. Protein biosynthesis and photosynthesis were down-regulated and genes of gametogenesis activated. A notable finding was that the genes encoding photosynthetic accessory PSBS proteins of currently unclear function in C. reinhardtii were strongly expressed following N-deprivation, providing a clue to their physiological role. Lipase-encoding genes were found to be some of the most regulated following N-deprivation, suggesting a remodeling of membranes under these conditions. The data provided here represent a rich source for the exploration of the mechanism of oil accumulation in microalgae. Examining N-replete and N-deprived conditions. Three biological replicates each condition.

ORGANISM(S): Chlamydomonas reinhardtii

SUBMITTER: Guangxi Wu

PROVIDER: E-GEOD-24365 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Changes in transcript abundance in Chlamydomonas reinhardtii following nitrogen deprivation predict diversion of metabolism.

Miller Rachel R Wu Guangxi G Deshpande Rahul R RR Vieler Astrid A Gärtner Katrin K Li Xiaobo X Moellering Eric R ER Zäuner Simone S Cornish Adam J AJ Liu Bensheng B Bullard Blair B Sears Barbara B BB Kuo Min-Hao MH Hegg Eric L EL Shachar-Hill Yair Y Shiu Shin-Han SH Benning Christoph C

Plant physiology 20101008 4

Like many microalgae, Chlamydomonas reinhardtii forms lipid droplets rich in triacylglycerols when nutrient deprived. To begin studying the mechanisms underlying this process, nitrogen (N) deprivation was used to induce triacylglycerol accumulation and changes in developmental programs such as gametogenesis. Comparative global analysis of transcripts under induced and noninduced conditions was applied as a first approach to studying molecular changes that promote or accompany triacylglycerol acc ...[more]

PMID: 20935180

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Project description:The Chlamydomonas reinhardtii transcriptome was characterized from nutrient-replete and sulfur-depleted wild-type and snrk2.1 mutant cells; the mutant is null for the regulatory serine-threonine kinase SNRK2.1, which is required for acclimation to sulfur deprivation. The transcriptome analyses involved microarray hybridization and RNA-seq technology; RT-qPCR evaluation of the data obtained by these techniques showed that RNA-seq is significantly more quantitative than microarray hybridizations. Sulfur-deprivation-responsive transcripts included those encoding proteins involved in sulfur acquisition and assimilation, recycling of sulfur-containing amino acids, synthesis of reduced sulfur metabolites and cofactors, and modification of cellular structures such as the cell wall and complexes associated with the photosynthetic apparatus. Moreover, the data suggest that cells deprived of sulfur favors accumulation of proteins with fewer sulfur-containing amino acids. Most of these sulfur-deprivation responses are controlled by the SNRK2.1 kinase. Furthermore, the snrk2.1 mutant exhibits a set of unique responses during both sulfur-replete and sulfur-depleted conditions that are not observed in wild-type cells. Many of these responses are likely to be elicited by singlet O2 accumulation in the mutant cells. The transcriptome results for the wild-type and mutant cells strongly suggest the occurrence of massive changes in cellular physiology and metabolism as the cells become depleted for sulfur, and reveal aspects of acclimation that are likely critical for cell survival. The three supplementary files GSE17970_supplemental_table_*.xls below include results of the differential expression analysis (expression estimates, fold changes and p-values), and different clusters of functionally related genes. Chlamydomonas strains used for this study were D66 (wt strain; nit2 cw15 mt+), ars11 (snrk2.1cw15mt+), 21gr (wt strain; nit5 mt-) and sac1 (sac1mt+). The ars11 strain was designated as the snrk2.1 mutant throughout since the lesion is in the SNRK2.1 gene. Cells were cultured under continuous light of ~60 M-NM-<mol photon m-2s-1 at 23M-BM-:C in liquid and on solid Tris-Acetate-Phosphate (TAP) medium. To impose S deprivation, cells in mid-logarithmic growth phase were washed twice with liquid TAP medium without S (TAP-S), and equal numbers of cells were resuspended in TAP or TAP-S. Cell aliquots were collected for RNA isolation just prior to and 6 h after being transferred to TAP and TAP-S medium. Total RNA from wt (D66) and snrk2.1 mutant cells after 0 and 6 h of being transferred to -S medium were submitted to Illumina for sequencing using their proprietary Genome Analyzer. cDNA libraries were assembled according to the manufacturerM-bM-^@M-^Ys RNA-seq protocol, loaded and sequenced as 35-mers in a total of 11 Solexa lanes. Raw image files were collected by the sequencer and analyzed using the standard Solexa pipeline.

Project description:A prominent enzyme in organellar RNA metabolism is the exoribonuclease polynucleotide phosphorylase (PNPase), whose reversible activity is governed by the nucleotides diphosphate-inorganic phosphate ratio. In Chlamydomonas reinhardtii, PNPase regulates chloroplast transcript accumulation in response to phosphorus (P) starvation, and PNPase expression is repressed by the response regulator PSR1 under these conditions. Here, we investigated the role of PNPase in the Arabidopsis (Arabidopsis thaliana) P deprivation response by comparing wild-type and pnp mutant plants with respect to their morphology, metabolite profiles, and transcriptomes. We found that P-deprived pnp mutants develop aborted clusters of lateral roots, which are characterized by decreased auxin responsiveness and cell division, and exhibit cell death at the root tips. Electron microscopy revealed that the collapse of root organelles is enhanced in the pnp mutant under P deprivation and occurred with low frequency under P-replete conditions. Global analyses of metabolites and transcripts were carried out to understand the molecular bases of these altered P deprivation responses. We found that the pnp mutant expresses some elements of the deprivation response even when grown on a full nutrient medium, including altered transcript accumulation, although its total and inorganic P contents are not reduced. The pnp mutation also confers P status-independent responses, including but not limited to stress responses. Taken together, our data support the hypothesis that the activity of the chloroplast PNPase is involved in plant acclimation to P availability and that it may help maintain an appropriate balance of P metabolites even under normal growth conditions. Experiment Overall Design: For each timepoints (3h and one week), we compared WT and pnp1-1 on +P and on -P, so a total of eight conditions For each condition, three biological replicates of at least 4 seedlings (without roots) were analyzed.

Dataset Information

RNA-seq of Chlamydomonas reinhardtii response to nitrogen deprivation

Publications

Changes in transcript abundance in Chlamydomonas reinhardtii following nitrogen deprivation predict diversion of metabolism.

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