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Serine/threonine protein kinase SpkG is a candidate for high salt resistance in the unicellular cyanobacterium Synechocystis sp. PCC 6803.

Liang C, Zhang X, Chi X, Guan X, Li Y, Qin S, Shao HB - PLoS ONE (2011)

Bottom Line: To further confirm the function of spkG, we also examined the effect of mutation of spkG on the expression of salt stress-inducible genes.We compared genome-wide patterns of transcription between wild-type Synechocystis sp.Our microarray experiment may help select relatively significant genes for further research on mechanisms of signal transduction of Synechocystis sp.

View Article: PubMed Central - PubMed

Affiliation: Qingdao University of Science and Technology, Qingdao, China.

ABSTRACT

Background: Seven serine/threonine kinase genes have been predicted in unicellular cyanobacterium Synechocystis sp. PCC6803. SpkA and SpkB were shown to be required for cell motility and SpkE has no kinase activity. There is no report whether the other four STKs are involved in stress-mediated signaling in Synechocystis PCC6803.

Methodology/principal findings: In this paper, we examined differential expression of the other four serine/threonine kinases, SpkC, SpkD, SpkF and SpkG, at seven different stress conditions. The transcriptional level was up-regulated of spkG and down-regulated of spkC under high salt stress condition. Two spk deletion mutants, ΔspkC and ΔspkG, were constructed and their growth characteristic were examined compared to the wild strain. The wild strain and ΔspkC mutant were not affected under high salt stress conditions. In contrast, growth of spkG mutant was completely impaired. To further confirm the function of spkG, we also examined the effect of mutation of spkG on the expression of salt stress-inducible genes. We compared genome-wide patterns of transcription between wild-type Synechocystis sp. PCC6803 and cells with a mutation in the SpkG with DNA microarray analysis.

Conclusion: In this study, we first study the spkG gene as sensor of high salt signal. We consider that SpkG play essential roles in Synechocystis sp. for sensing the high salt signal directly, rather than mediating signals among other kinases. Our microarray experiment may help select relatively significant genes for further research on mechanisms of signal transduction of Synechocystis sp. PCC6803 under high salt stress.

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Semiquantitative RT-PCR reveals the transcriptional dynamics of spkC, spkD, spkF and spkG at different conditions.The transcript level of RNase P in each sample serves as a control. N, normal conditions; LT, low temperature; HT, high temperature; HS, high salt; −C, carbon-deficient; −N, nitrogen-deficient; −P, phosphorus-deficient. The normal cultivation condition and all stress conditions have been detailed in Materials and methods.
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pone-0018718-g001: Semiquantitative RT-PCR reveals the transcriptional dynamics of spkC, spkD, spkF and spkG at different conditions.The transcript level of RNase P in each sample serves as a control. N, normal conditions; LT, low temperature; HT, high temperature; HS, high salt; −C, carbon-deficient; −N, nitrogen-deficient; −P, phosphorus-deficient. The normal cultivation condition and all stress conditions have been detailed in Materials and methods.

Mentions: To investigate whether the four STKs are involved in stress-mediated signaling in Synechocystis PCC6803, the expression of spkC, spkD, spkF and spkG were examined under a variety of stress conditions by semi-quantitative RT-PCR. Total RNA isolated from Synechocystis PCC6803 untreated and stress-treated cells was used to amplify spkC, spkD, spkF and spkG cDNA. The amplified RT-PCR fragment was confirmed by cloning and sequencing. Semi-quantitative RT-PCR expression analysis showed that under standard conditions, spkC and spkD showed relatively high levels compared to spkG (Fig. 1), and there was no detective expression of spkF. A severe decrease was observed in mRNA accumulation for spkC after the treatment of high salt stress and a moderate decrease was detected after the treatment of nitrogen deprivation and high light stress. The levels of spkC transcripts under other stress conditions did not vary significantly. This suggested that the expression of spkC were down-regulated under high salt conditions. The expression levels of spkD did not vary significantly under normal and different stress conditions but was relatively higher compared to the others, consistent with the fact that it is essential for survival,which could not be knocked out completely [17]. No expression of spkF could be detected under any condition (data not shown). After exposure to high salt stress, the expression level of spkG was increased to a significantly extent. A densitometry measurement showed that the induced level of spkG transcripts s about 1.3±0.02-fold higher than the constitutive level(Fig. 1), while the other stress conditions had no effect on the transcription level. The up-regulated expression of spkG suggested a mechanism of positive regulation under high salt stress. In two-component signal transduction systems, most histidine kinases are known to respond to stress by post-translational alterations and regulatory proteins could be affected at both the transcriptional and post-transcriptional levels [19]–[22]. Also, in Rice, calmodulin-dependent serine/threonine phosphatase was reported to be involved in the process of salt stress tolerance [23]. We examined the transcriptional levels of serine/threonine kinases using RT-PCR and our results suggested that, in Synechocystis at least, STKs could respond to stress conditions by controlling their expression levels.


Serine/threonine protein kinase SpkG is a candidate for high salt resistance in the unicellular cyanobacterium Synechocystis sp. PCC 6803.

Liang C, Zhang X, Chi X, Guan X, Li Y, Qin S, Shao HB - PLoS ONE (2011)

Semiquantitative RT-PCR reveals the transcriptional dynamics of spkC, spkD, spkF and spkG at different conditions.The transcript level of RNase P in each sample serves as a control. N, normal conditions; LT, low temperature; HT, high temperature; HS, high salt; −C, carbon-deficient; −N, nitrogen-deficient; −P, phosphorus-deficient. The normal cultivation condition and all stress conditions have been detailed in Materials and methods.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3102658&req=5

pone-0018718-g001: Semiquantitative RT-PCR reveals the transcriptional dynamics of spkC, spkD, spkF and spkG at different conditions.The transcript level of RNase P in each sample serves as a control. N, normal conditions; LT, low temperature; HT, high temperature; HS, high salt; −C, carbon-deficient; −N, nitrogen-deficient; −P, phosphorus-deficient. The normal cultivation condition and all stress conditions have been detailed in Materials and methods.
Mentions: To investigate whether the four STKs are involved in stress-mediated signaling in Synechocystis PCC6803, the expression of spkC, spkD, spkF and spkG were examined under a variety of stress conditions by semi-quantitative RT-PCR. Total RNA isolated from Synechocystis PCC6803 untreated and stress-treated cells was used to amplify spkC, spkD, spkF and spkG cDNA. The amplified RT-PCR fragment was confirmed by cloning and sequencing. Semi-quantitative RT-PCR expression analysis showed that under standard conditions, spkC and spkD showed relatively high levels compared to spkG (Fig. 1), and there was no detective expression of spkF. A severe decrease was observed in mRNA accumulation for spkC after the treatment of high salt stress and a moderate decrease was detected after the treatment of nitrogen deprivation and high light stress. The levels of spkC transcripts under other stress conditions did not vary significantly. This suggested that the expression of spkC were down-regulated under high salt conditions. The expression levels of spkD did not vary significantly under normal and different stress conditions but was relatively higher compared to the others, consistent with the fact that it is essential for survival,which could not be knocked out completely [17]. No expression of spkF could be detected under any condition (data not shown). After exposure to high salt stress, the expression level of spkG was increased to a significantly extent. A densitometry measurement showed that the induced level of spkG transcripts s about 1.3±0.02-fold higher than the constitutive level(Fig. 1), while the other stress conditions had no effect on the transcription level. The up-regulated expression of spkG suggested a mechanism of positive regulation under high salt stress. In two-component signal transduction systems, most histidine kinases are known to respond to stress by post-translational alterations and regulatory proteins could be affected at both the transcriptional and post-transcriptional levels [19]–[22]. Also, in Rice, calmodulin-dependent serine/threonine phosphatase was reported to be involved in the process of salt stress tolerance [23]. We examined the transcriptional levels of serine/threonine kinases using RT-PCR and our results suggested that, in Synechocystis at least, STKs could respond to stress conditions by controlling their expression levels.

Bottom Line: To further confirm the function of spkG, we also examined the effect of mutation of spkG on the expression of salt stress-inducible genes.We compared genome-wide patterns of transcription between wild-type Synechocystis sp.Our microarray experiment may help select relatively significant genes for further research on mechanisms of signal transduction of Synechocystis sp.

View Article: PubMed Central - PubMed

Affiliation: Qingdao University of Science and Technology, Qingdao, China.

ABSTRACT

Background: Seven serine/threonine kinase genes have been predicted in unicellular cyanobacterium Synechocystis sp. PCC6803. SpkA and SpkB were shown to be required for cell motility and SpkE has no kinase activity. There is no report whether the other four STKs are involved in stress-mediated signaling in Synechocystis PCC6803.

Methodology/principal findings: In this paper, we examined differential expression of the other four serine/threonine kinases, SpkC, SpkD, SpkF and SpkG, at seven different stress conditions. The transcriptional level was up-regulated of spkG and down-regulated of spkC under high salt stress condition. Two spk deletion mutants, ΔspkC and ΔspkG, were constructed and their growth characteristic were examined compared to the wild strain. The wild strain and ΔspkC mutant were not affected under high salt stress conditions. In contrast, growth of spkG mutant was completely impaired. To further confirm the function of spkG, we also examined the effect of mutation of spkG on the expression of salt stress-inducible genes. We compared genome-wide patterns of transcription between wild-type Synechocystis sp. PCC6803 and cells with a mutation in the SpkG with DNA microarray analysis.

Conclusion: In this study, we first study the spkG gene as sensor of high salt signal. We consider that SpkG play essential roles in Synechocystis sp. for sensing the high salt signal directly, rather than mediating signals among other kinases. Our microarray experiment may help select relatively significant genes for further research on mechanisms of signal transduction of Synechocystis sp. PCC6803 under high salt stress.

Show MeSH
Related in: MedlinePlus