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Transcriptome analysis of the phytopathogen Xylella fastidiosa in response to salt and osmotic stress

ABSTRACT: The global transcriptional response of the phytopathogenic bacterium X. fastidiosa to a sudden increase in salinity and osmolarity of the medium was investigated using DNA microarrays. Time-course experiments were carried out by exposing bacterial cells to high salinity (250 mM NaCl) and high osmolarity (300 mM sucrose) conditions revealing 142 upregulated genes under both stresses, including pathogenicity related genes, genes encoding transcriptional regulators, as well as genes related to DNA metabolism and mobile genetic elements. In addition, 38 genes were downregulated under both conditions, most of them related to ribosomal and heat shock proteins. A total of 192 genes were upregulated exclusively in the presence of NaCl, including genes encoding transporters, genes involved in oxidative-stress response and genes related to cell structure. A smaller number of genes (44 genes) were induced only in the presence of sucrose, most of them encoding hypothetical and conserved hypothetical proteins. Interestingly, 57% of the genes differentially expressed under both stress conditions have no putative function assigned, emphasizing the importance of high-throughput experiments to start the characterization of these genes in X. fastidiosa. Keywords: stress response, osmotic and salt stress

ORGANISM(S): Xylella fastidiosa

PROVIDER: GSE7126 | GEO | 2014/05/25

SECONDARY ACCESSION(S): PRJNA98207

REPOSITORIES: GEO

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Project description:Algae of the genus Dunaliella are known to be able to grow in a wide range of salinities. To investigate which genes may be important for growth under extremely low or high salinities, a survey of the Dunaliella sp. transcriptome was performed by microarray analysis. For the cDNA microarray 778 expressed sequence tags (ESTs) were generated from a cDNA library of Dunaliella sp. The cDNA microarray was used to compare the transcription profile of cells that were acclimated to extreme saline conditions (0.08 M and 4.5 M NaCl) with the transcription profile of cells acclimated to an intermediate salinity at 1.5 M NaCl. The comparative microarray analysis indicated that 211 out of the 778 ESTs differed in their expression levels more than two-fold in cells grown at extreme different salinity when compared to cells grown at intermediate salinity (1.5M NaCl). The sequences of these 211 cDNAs were classified into 169 non-redundant gene clusters. Of these genes, the expression of 36 genes was increased and 69 genes were suppressed in cells grown at low salinity. The expression of 49 genes was increased and 85 genes were suppressed in cells grown at high salinity. One-hundred thirty four genes have been revealed to show up- and down-regulation by high salinity (4.5M NaCl). Of the high salinity-regulated genes 52% were also influenced by low salinity (0.08M NaCl), revealing a dense overlap between low and high salt responses. Only 35 genes are regulated independently by low salt condition. Strong relationships, however, were observed in the expression of these extreme salinity-responsive genes based on Venn diagram analysis, which found 70 genes that responded to these two salinity conditions. Refined expression analysis using gene-specific primers and real-time PCR for selected transcripts was in agreement with microarray results for most genes tested. This study provides the first large-scale survey of the transcriptome in the microalga Dunaliella sp. and it provides a platform for further functional investigation of differentially expressed genes in Dunaliella. Keywords: Low salt(0.08M NaCl) or high salt(4.5M NaCl)-acclimated cells

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Transcriptome analysis of the phytopathogen Xylella fastidiosa in response to salt and osmotic stress

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