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Phosphate Starvation in Chlamydomonas reinhardtii

ABSTRACT: 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.

ORGANISM(S): Chlamydomonas reinhardtii

PROVIDER: GSE56505 | GEO | 2014/04/05

SECONDARY ACCESSION(S): PRJNA243546

REPOSITORIES: GEO

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Project description:Herein we demonstrate the efficacy of an unbiased proteomics screening approach for studying protein expression changes in the KC-Tie2 psoriasis mouse model, identifying multiple protein expression changes in the mouse and validating these changes in human psoriasis. KC-Tie2 mouse skin samples (n=3) were compared with littermate controls (n=3) using gel-based fractionation followed by label-free protein expression analysis. 5482 peptides mapping to 1281 proteins were identified and quantitated: 105 proteins exhibited fold-changes ≥2.0 including: stefin A1 (average fold change of 342.4 and an average P = 0.0082; cystatin A, human orthologue); slc25a5 (average fold change of 46.2 and an average P = 0.0318); serpinb3b (average fold change of 35.6 and an average P = 0.0345; serpinB1, human orthologue); and kallikrein related peptidase 6 (average fold change of 4.7 and an average P = 0.2474; KLK6). We independently confirmed mouse gene expression-based increases of selected genes including serpinb3b (17.4-fold, P < 0.0001), KLK6 (9.0-fold, P = 0.002), stefin A1 (7.3-fold; P < 0.001) and slc25A5 (1.5-fold; P = 0.05) using qRT-PCR on a second cohort of animals (n=8). Parallel LC/MS/MS analyses on these same samples verified protein-level increases of 1.3-fold (slc25a5; P < 0.05), 29,000-fold (stefinA1; P < 0.01), 322-fold (KLK6; P < 0.0001) between KC-Tie2 and control mice. To underscore the utility and translatability of our combined approach, we analyzed gene and protein expression levels in psoriasis patient skin and primary keratinocytes vs. healthy controls. Increases in gene expression for slc25a5 (1.8-fold), cystatin A (3.0-fold), KLK6 (5.8-fold) and serpinB1 (76-fold; all P < 0.05) were observed between healthy controls and involved lesional psoriasis skin and primary psoriasis keratinocytes. Moreover slc25a5, cystatin A, KLK6 and serpinB1 protein were all increased in lesional psoriasis skin compared to normal skin. These results highlight the usefulness of preclinical disease models using readily-available mouse skin and demonstrate the utility of proteomic approaches for identifying novel peptides/proteins that are differentially regulated in psoriasis that could serve as sources of auto-antigens or provide novel therapeutic targets for the development of new anti-psoriatic treatments.

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Phosphate Starvation in Chlamydomonas reinhardtii

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