Serine/Threonine Protein Kinase SpkG Is a Candidate for High Salt Resistance in the Unicellular Cyanobacterium Synechocystis sp. PCC 6803

Chengwei Liang,Xiangyu Guan,Xiaoyuan Chi,Song Qin,Xiaowen Zhang,Youxun Li,Hong Bo Shao,Vladimir N Uversky

doi:10.1371/journal.pone.0018718

Abstract

BackgroundSeven 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 FindingsIn 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.ConclusionIn 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.

Highlights

Cyanobacteria are photoautotrophic prokaryotes able to grow in a wide range of ecological environments, so their signal transduction systems, which perceive and transduce environmental signals, are important in the acclimation to the environmental changes
To investigate whether the four specific protein kinases (STK) 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
Semi-quantitative reverse transcription PCR To investigate whether the four STKs are involved in stressmediated 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

Summary

Introduction

Cyanobacteria are photoautotrophic prokaryotes able to grow in a wide range of ecological environments, so their signal transduction systems, which perceive and transduce environmental signals, are important in the acclimation to the environmental changes. Genome sequence data of Synechocystis has predicted the presence of 7 serine/threonine kinase (PKN2 type) genes, named spkA (sll1574–1575), spkB (slr1697), spkC (slr0599), spkD (sll0776), spkE (slr1443), spkF (slr1225) and spkG [15]. Environmental stresses trigger a wide variety of plant responses, ranging from altered gene expression and cellular metabolism to changes in growth rate and plant productivity [18]. 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. In order to better understand the function of spkG and spkC and their importance in salt stress, we constructed a knockout mutant and compared the feature of this strain to that of the wild-type in the presence and absence of high salt 855 mM NaCl (0.5 g/l NaCl). There is no report whether the other four STKs are involved in stress-mediated signaling in Synechocystis PCC6803

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Results

Conclusion