A deletion mutation in the spacing within the psaA core promoter enhances transcription in a cyanobacterium Synechocystis sp. PCC 6803.
A deletion mutation in the spacing within the psaA core promoter enhances transcription in a cyanobacterium Synechocystis sp. PCC 6803.
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DOI：
10.1093/pcp/pcr159
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发表时间：
2012
影响因子：
4.9
通讯作者：
T. Midorikawa;R. Narikawa;M. Ikeuchi
中科院分区：
文献类型：
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作者：
T. Midorikawa;R. Narikawa;M. Ikeuchi
PSI反应中心psaA的转录调控是对环境变化的重要生理反应之一。我们之前报道过 Rrf2 型转录调节因子 Slr0846 激活集胞藻中 psaA 的转录。 PCC 6803。在Δslr0846突变体中，来自两个启动子P1和P2的转录物被下移，结果观察到叶绿素含量较低和生长较慢。在这里，我们报告了恢复叶绿素积累和光合自养生长的自发抑制因子。整个启动子区域的测序显示，在一些抑制子中，9 bp G 片段（P1 转录起始点的 -21 到 -29）中存在相同的单核苷酸缺失，该片段位于 P1 核心启动子的 -35 和 -10 元件之间（以下称为 -G 突变）。该假回复体中 P1 的转录本丰度高于 Δslr0846 突变体。当启动子与报告基因融合时，-G 突变的表达量比野生型启动子高约 4 倍。研究表明，psaA 的 P1 启动子活性受到 -35 上游的强光调节元件 1 的调节。 -G突变的P1启动子仍然保留高光响应。因此，-G 突变增强了 psaA 的表达水平，而不会损失对强光条件的响应。这是第一个关于蓝藻表达启动子间隔长度自发突变的研究。
Transcriptional regulation of PSI reaction center psaA is one of the important physiological responses to changing environments. We previously reported that the Rrf2-type transcriptional regulator Slr0846 activates transcription of psaA in Synechocystis sp. PCC 6803. In the Δslr0846 mutant, transcripts from two promoters, P1 and P2, were downshifted and, as a result, a lower Chl content and slower growth were observed. Here, we report spontaneous suppressors which recovered Chl accumulation and photoautotrophic growth. Sequencing of the whole promoter region revealed in some suppressors the same single nucleotide deletion in a 9 bp G stretch (-21 to -29 from the transcriptional start point of P1), which is located between the -35 and -10 elements of the P1 core promoter (hereafter the -G mutation). The transcripts from P1 were higher in abundance in this pseudorevertant than in the Δslr0846 mutant. When the promoter was fused to a reporter gene, the -G mutation conferred ~4 times higher expression than the wild-type promoter. It has been shown that the P1 promoter activity of psaA is regulated by a high light regulatory element 1 just upstream of -35. The -G mutated P1 promoter still retained the high light response. Thus, the -G mutation enhanced the expression level of psaA without a loss of the response to the high light conditions. This is the first study of the spontaneous mutation of a spacer length of a promoter for expression in cyanobacteria.