集胞藻PCC 6803中丝氨酸/苏氨酸激酶SpkC对高温胁迫的响应

Response of serine/threonine protein kinase SpkC to high temperature stress in Synechocystis sp. PCC 6803

摘要:

丝氨酸/苏氨酸激酶是蓝藻感知和转导外界刺激的重要元件，但至今蓝藻中很多丝氨酸/苏氨酸激酶的功能尚属未知。[目的]研究集胞藻PCC 6803中的丝氨酸/苏氨酸激酶SpkC是否参与对高温胁迫的响应。[方法]本研究采用同源重组的方法构建spkC基因完全敲除突变株，检测突变株与野生株在高温胁迫下的生长状况、色素组成，并对高温胁迫下叶绿素荧光参数差异进行分析，比较光合系统Ⅱ活性差异。此外，通过测定生长速率来判断高温胁迫后藻株的恢复情况。[结果]经过42℃高温胁迫后，与野生株相比，突变株ΔspkC生长减缓，光合色素（叶绿素、类胡萝卜素和藻胆色素）的含量降低；45℃高温胁迫下突变株ΔspkC的光合系统Ⅱ活性下降幅度更大；经过5 d 42℃高温处理后，突变株生长几乎停滞，存活率较野生株明显降低。[结论]集胞藻PCC 6803中spkC基因的缺失导致突变株对高温胁迫响应出现缺陷，提示丝氨酸/苏氨酸激酶SpkC参与响应高温胁迫。

Abstract:

Serine/threonine protein kinases play important roles to sense and transduce signal to cope with external environment. However, functions of many serine/threonine protein kinases in cyanobacteria are still unknown. [Objective] This study aims to explore whether SpkC in Synechocystis sp. PCC 6803 responses to high temperature stress. [Methods] We used the homologous recombination method to construct the spkC gene knockout mutant (ΔspkC), and then compared the growth rate, pigment contents of ΔspkC mutant and the wild strain under high temperature stress. In addition, we detected chlorophyll fluorescence under high temperature stress. Recoveries of ΔspkC and wild strain from high-temperature stress were determined through measuring the growth rate under normal temperature. [Results] Compared with wild type strain, ΔspkC mutant grew slower, and the contents of three photosynthetic pigments (chlorophyll, carotenoid and phycobilin) decreased after high temperature stress at 42℃. The activity of photosynthetic system Ⅱ in ΔspkC decreased more rapidly at 45℃. What's more, ΔspkC strain was not able to recover after high-temperature stress for 5 days; their survival rate was significantly lower than wild-type. [Conclusion] The deletion of spkC led to severe defect response to high-temperature stress in Synechocystis sp. PCC 6803, which suggests that serine/threonine protein kinase SpkC is involved in response processes against high temperature stress.