Project description:This SuperSeries is composed of the following subset Series: GSE33039: replication experiment GSE33040: Sulfur starvation experiment in Chlamydomonas GSE33041: Chlamydomonas growth under nitrogen starvation Refer to individual Series
Project description:In the actual context of climate changing environments, photosynthetic organisms need to adapt to more extreme conditions. Microalgae can be excellent organisms to understand molecular mechanisms that activate survival mechanisms under stress. Chlamydomonas reinhardtii signaling mutants are extremely useful to decipher which strategies they use to cope with changeable environments. In this study, we conducted prolonged starvation in wild type and vip1-1 Chlamydomonas cells. The mutant vip1-1 has an altered profile of pyroinositol polyphosphates (PP-InsPs) which are signaling molecules present in all eukaryotes. These molecules have been connected to P signaling in other organisms including plants but their implications in other nutrient signaling is still under evaluation. After prolonged starvation, WT and vip1-1 showed important differences in the levels of chlorophyll and PSII activity. We also performed a metabolomic analysis under these conditions and found an overall decrease in different organic compounds such as amino acids including arginine and its precursors and tryptophan which is considered as a signaling molecule itself in plants. In addition, we observed significant differences in RNA levels of genes related to nitrogen assimilation that are under the control of NIT2 transcription factor. Overall our data indicate an important role of PP-InsPs in the regulation of nutrient starvation especially regarding N assimilation and C distribution. These data are of great importance for the generation of resilient strains to be used in open ponds and high capacity bioreactors.
Project description:Here, we report on the transcriptome of the organelles of the micro-alga, Chlamydomonas reinhardtii, sampled under a number of different conditions. The preparation of the RNA-Seq libraries and their analysis were performed using protocols optimized for organellar transcripts. Samples include growth in media +/– Fe, growth in media +/– Cu, diurnal growth samples collected in dark and light, and the sexual cycle.
Project description:Phosphorus (P) is an essential nutrient that is limiting in many environments. When P is scarce organisms employ strategies for conservation of internal stores, and to efficiently scavenge P from their external surroundings. In this study we investigated the acclimation response of Chlamydomonas reinhardtii to P deficiency, comparing the transcriptional profiles of P starved wild-type cells to the P replete condition. RNA was prepared from P-containing or P-deprived logarithmic growth phase cells and subjected to RNA-Seq analysis. During the 24 hours after the imposition of P starvation we observed that from the 407 significantly changing genes (> 2 fold change, corrected p-value < 0.05) in the wild-type 317 genes were up-regulated, in average 8.36-fold, and 90 genes were down-regulated by 3.43-fold, in average. Many of the upregulated genes encoded enzymes involved in specific responses to P starvation, including PHOX, encoding the major secreted alkaline phosphatase, and multiple putative, high-efficiency phosphate transporter genes. More general responses included the up-regulation of genes involved in photoprotective processes (LHCSR3, LHCSR1, LHCBM9, PTOX1) and genes involved in protein modification and degradation. Down-regulated mRNAs indicated an early stage of the reduction of chloroplast ribosomal proteins, which are considered to be a reservoir for P in the cell.
Project description:Photosynthetic organisms coordinate their metabolism and growth with diurnal light, which can range in intensity from limiting to inhibitory. To gain a comprehensive understanding of how diurnal regulatory circuits interface with sensing and response to various light intensities, we performed a systems analysis of synchronized Chlamydomonas reinhardtii populations acclimated to low, moderate, and high diurnal light. Transcriptomic and proteomic data revealed that Chlamydomonas’ rhythmic gene expression program is resilient to limiting and excess light. Although gene expression is dynamic over the diurnal cycle, Chlamydomonas populations acclimated to low and high diurnal light exhibit constitutive phenotypes with respect to photosystem abundance, thylakoid architecture, and non-photochemical quenching that persist through the night. This suggests that cells harbor a “memory” or anticipation of the daylight environment. The integrated data constitute an excellent resource for understanding gene regulatory mechanisms and photoprotection in eukaryotes under environmentally relevant conditions.
Project description:Small RNAs (21-24 nt) are pivotal regulators of gene expression that guide both transcriptional and post-transcriptional silencing mechanisms in diverse eukaryotes, including most if not all plants. MicroRNAs (miRNAs) and short interfering RNAs (siRNAs) are the two major types, both of which have a demonstrated and important role in plant development, stress responses and pathogen resistance. In this work, we used a deep sequencing approach (Sequencing-By-Synthesis, or SBS) to develop sequence resources of small RNAs from cultures of Chlamydomonas reinhardtii (in control, phosphate starvation and sulphate starvation conditions). The high depth of the resulting datasets enabled us to examine in detail critical small RNA features as size distribution, tissue-specific regulation and sequence conservation between different organs in this species. We also developed database resources and a dedicated website (http://smallrna.udel.edu/) with computational tools for allowing other users to identify new miRNAs or siRNAs involved in specific regulatory pathways, verify the degree of conservation of these sequences in other plant species and map small RNAs on genes or larger regions of the genome under study.
Project description:Phosphorus (P) is an essential nutrient that is limiting in many environments. When P is scarce organisms employ strategies for conservation of internal stores, and to efficiently scavenge P from their external surroundings. In this study we investigated the acclimation response of Chlamydomonas reinhardtii to P deficiency, comparing the transcriptional profiles of P starved wild-type cells to the P replete condition. RNA was prepared from P-containing or P-deprived logarithmic growth phase cells and subjected to RNA-Seq analysis. During the 24 hours after the imposition of P starvation we observed that from the 407 significantly changing genes (> 2 fold change, corrected p-value < 0.05) in the wild-type 317 genes were up-regulated, in average 8.36-fold, and 90 genes were down-regulated by 3.43-fold, in average. Many of the upregulated genes encoded enzymes involved in specific responses to P starvation, including PHOX, encoding the major secreted alkaline phosphatase, and multiple putative, high-efficiency phosphate transporter genes. More general responses included the up-regulation of genes involved in photoprotective processes (LHCSR3, LHCSR1, LHCBM9, PTOX1) and genes involved in protein modification and degradation. Down-regulated mRNAs indicated an early stage of the reduction of chloroplast ribosomal proteins, which are considered to be a reservoir for P in the cell. Chlamydomonas reinhardtii strain 21 gr (CC1690, wild-type) grown in TAP medium (Harris 1989) in a rotary incubator (200 rpm) at 25 M-BM-0C in continuous light (70 M-BM-5mol m-2 s-1). For 24 hours, either 1.1 mM phosphate or 0 mM were provided with the growth media. P deprivation was achieved by washing cells twice in midlogarithmic growth phase with liquid TAP medium without P (TAP-P) and cells were resuspended at a density of 2.5 mg/ml Chlorophyll in TAP or TAP-P. Cell aliquots were collected for mRNA isolation 24 h after being transferred either to TAP or TAP-P medium.