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Identification of a gene controlling levels of the copper response regulator 1 transcription factor in Chlamydomonas reinhardtii

ABSTRACT: Oxygen prevents hydrogen production in Chlamydomonas (Chlamydomonas reinhardtii), in part by inhibiting the transcription of hydrogenase genes. We developed a screen for mutants showing constitutive accumulation of iron hydrogenase 1 (HYDA1) transcripts in normoxia. A reporter gene required for ciliary motility placed under the control of the HYDA1 promoter conferred motility only in hypoxia. By selecting for mutants able to swim even in normoxia, we obtained strains that constitutively express the reporter gene. One identified mutant was affected in a gene encoding an F-box protein 3 (FBXO3) that participates in ubiquitylation and proteasomal degradation pathways in other eukaryotes. Transcriptome profiles revealed that the mutation, termed cehc1-1 (constitutive expression of hydrogenases and copper-responsive genes), triggers the upregulation of genes known to be targets of copper response regulator 1 (CRR1), a transcription factor involved in the nutritional copper signaling pathway and in the hypoxia response pathway. CRR1 was required for upregulating the HYDA1 reporter gene expression in response to hypoxia and for the constitutive expression of the reporter gene in cehc1-1 mutant cells. The CRR1 protein, normally degraded in Cu-supplemented cells, was stabilized in cehc1-1 cells, supporting the conclusion that CEHC1 facilitates CRR1 degradation. Our results describe a previously unknown pathway for CRR1 inhibition and possibly other pathways leading to complex metabolic changes.

ORGANISM(S): Chlamydomonas reinhardtii

PROVIDER: GSE252595 | GEO | 2025/01/09

REPOSITORIES: GEO

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			Action	DRS
		Other
	GSE252595_CEHC1_study.mean_FPKMs.tsv.gz	Tabular
	GSE252595_CEHC1_study.replicates_FPKMs.tsv.gz	Tabular

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Project description:The absence of oxygen (O2) is a stress condition for aerobic organisms and requires extensive acclimation responses. Previously, Chlamydomonas reinhardtii has been used as a reference organism for understanding these acclimation responses. In this work, we use RNA-Seq for a whole genome view of the acclimation of the organism to dark-anoxic conditions. To distinguish the responses dependent on the COPPER RESPONSE REGULATOR 1 (CRR1), which is also involved in hypoxic gene regulation, we compared the transcriptome of crr1 mutants to that of complemented strains. Nearly 10% of the genome (~ 1,400 genes) are affected by hypoxia based on pairwise comparisons of all strains and two time-points. Comparing transcript profiles from early (hypoxic) with those from late (anoxic) time-points indicated that the cells activated oxidative energy generation pathways before employing fermentative enzymes. Probable substrates included not only carbohydrates but also amino acids and fatty acids (FAs). Lipid profiling of the C. reinhardtii cells revealed that they degraded FAs but also accumulated triacylglycerols (TAGs). In contrast to N-deprived cells, the TAGs accumulating in hypoxic cells are enriched in desaturated FAs, which distinguishes the contribution of individual pathways for Chlamydomonas TAG accumulation. In crr1 mutants, about 140 genes were aberrantly regulated , re-affirming the importance of CRR1 for the hypoxic response, but indicating also the contribution of additional O2-sensors and signaling strategies to account for the remaining differentially regulated transcripts. We conclude that nitric oxide (NO) dependent signaling cascades, employing both known and novel components, are operative in C. reinhardtii. The transcriptome of four different Chlamydomonas strains (wild type CC-124, crr1 mutant, crr1:CRR1 rescued strain and crr1dCys rescued strain) are profiled by RNA-Seq in the dark at different times after the transition from light-oxic to dark-anoxic conditions

Project description:Zinc is an essential nutrient because of its role in catalysis and in stabilizing protein structure, but excess zinc can also be deleterious. Four nutritional zinc states have been identified in the alga Chlamydomonas reinhardtii: zinc toxic, zinc replete, zinc deficient and zinc limited. Growth is inhibited in zinc-limited and zinc toxic cells relative to zinc-replete cells, while zinc-deficiency is visually asymptomatic but distinguished by the accumulation of transcripts encoding ZIP family transporters. To identify targets of zinc deficiency and mechanisms of zinc acclimation, we used RNA-seq to probe zinc nutrition responsive changes in gene expression. We identified a subset of genes encoding zinc-handling components, including ZIP family transporters and candidate zinc chaperones. In addition, we noted an impact on two other regulatory pathways, the carbon concentrating mechanism (CCM) and the nutritional copper regulon. Targets of transcription factor Ccm1 and various CAH genes are up-regulated in zinc-deficiency, as a likely consequence of reduced carbonic anhydrase activity, which is validated by mass spectrometry and immunoblot analysis of Cah1, Cah3 and Cah4. Chlamydomonas is therefore not able to grow photoautotrophically in air in zinc limiting conditions, but supplementation with 1% CO2 restores growth to wild-type rates, suggesting that the inability to maintain CCM is a major consequence of zinc limitation. Surprisingly, we noted also that the Crr1 regulon, which responds to Cu limitation, is also turned on in zinc deficiency, and in fact, Crr1 is required for growth in zinc-limiting conditions. Zinc deficient cells are functionally copper deficient, as evidenced by reduced plastocyanin abundance, even though they hyperaccumulate copper up to 50-fold over normal levels. We suggest that zinc-deficient cells sequester Cu in a bio-unavailable form, perhaps to prevent mis-metallation of critical zinc sites. Zn-limited wild-type cells were generated by transfer of cells from the first round of growth in medium with no supplemental Zn into TAP medium supplemented or not with 2.5 ÂµM Zn-EDTA The control samples for this study are represented in GSE25622

Project description:Recent evidence suggests that hypoxia caused by acute myocardial infarction (AMI) can induce evident cardiomyocyte apoptosis. Exosomes, as paracrine signaling mediators by delivering cytosolic components (including miRNA, mRNA, protein), play crucial roles in intercellular communication. However, the systemic regulation of exosome-mediated miRNA delivery and subsequent regulation effect underlying AMI are not well-understood to date. Here, using small RNA-seq, we investigated the miRNAome of H9C2 cells and corresponding paracrine exosmes after hypoxia stress, and identified total of 92 and 62 differentially expressed (DE) miRNAs in cells and exosomes from hypoxia vs. normoxia condition. We found that hypoxia strongly induced the expression of hypoxamiRs in H9C2 cells and altered cardiomyocyte-derived exosomal miRNAome. Functional enrichment analysis revealed extensive roles of DE exosomal miRNAs in HIF-1 signaling pathway and cell apoptosis process, such as TNF signaling pathway, MAPK signaling pathway, mTOR signaling pathway. Furthermore, the gain- and loss-of-function analysis demonstrated the anti-apoptotic effects of hypoxia-induced exosomal miRNAs, i.e. miR-21-5p, miR-378-3p, miR-152-3p, let-7i-5p, and then the luciferase reporter assay confirmed that miR-152-3p and let-7i-5p implemented their anti-apoptotic function by directly targeting Atg12 and Faslg, respectively. In short, this study revealed that hypoxia-exosomes derived from cardiomyocyte, loaded abundant cardio-protective miRNAs, mediate crosstalk among cardiomyocytes and prevent cardiomyocytes apoptosis after hypoxia. Methods: we established the anoxia model using H9C2 cells, an immortal cardiac muscle cell line, to imitate hypoxia condition caused by AMI in vitro, and then small RNA-seq were employed to investigate the miRNA transcriptome of H9C2 cells and its exosomes collected from hypoxia and normoxia culture medium. Results: we identified the miRNAome of H9C2 cells and its exosmes under both hypoxia and normoxia, including 331, 338, 144, 74 unique mature miRNAs from hypoxia-cells, normoxia-cells, hypoxia-exosomes, normoxia-exosomes, respectively. Total of 92 and 62 DE miRNAs were identified from cells and exosomes. Among of which, the DE exosomal miRNAs were mainly involved in HIF-1 signaling pathway and cell apoptosis process, such as TNF signaling pathway, MAPK signaling pathway, mTOR signaling pathway. Interestingly, we found that some DE exosomal miRNAs, including miR-21-5p, miR-378-3p, miR-152-3p, let-7i-5p, have an anti-apoptotic and pro-viability effects in H9C2 cells under hypoxic stress. In addition, Atg12 and Faslg to be respective target of miR-152-3p and let-7i-5p were partly elucidated the anti-apoptosis mechanism of hypoxia-exosomes. Conclusions:In brief, this study illustrated a potential mechanism that, under hypoxic stress, hypoxia pre-perceived cardiomyocytes can spontaneously secrete the hypoxamiRs enriched exosomes, loaded a large amount of cardio-protective miRNA, which mediate crosstalk among cardiomyocytes and prevent apoptosis to heighten the hypoxia adaptability of cardiomyocytes. In more detail, we first discovered that miR-152-3p and let-7i-5p, enriched in hypoxia-exosomes derived by cardiomyocytes, played an anti-apoptosis role via mitochondrial pathway(intrinsic pathway) and death receptor pathway (extrinsic pathway), respectively.

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Identification of a gene controlling levels of the copper response regulator 1 transcription factor in Chlamydomonas reinhardtii

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