Laboratory of Plant Molecular Improvement and Global Center of Excellence (COE) Program, Graduate School of Nutritional and Environmental Sciences, University of Shizuoka, Suruga, Shizuoka 422-8526, Japan.
Proc Natl Acad Sci U S A. 2010 Jun 8;107(23):10760-4. doi: 10.1073/pnas.0911692107. Epub 2010 May 24.
An imbalance in photosynthetic electron transfer is thought to be redressed by photosynthetic control of the rate of expression of genes encoding apoproteins of photosystem (PS)-I and PS-II in response to the redox state of plastoquinone (PQ), which is a connecting electron carrier. PS stoichiometry is then adjusted to enhance photosynthetic efficiency. In prokaryotes, sigma factors are well known for their participation in the control of RNA polymerase activity in transcription, whereas there have been no reports concerning their association with redox regulation. We have found that the phosphorylation of SIG1, the major sigma factor (SIG), is regulated by redox signals and selectively inhibits the transcription of the psaA gene, which encodes a PS-I protein. We produced transgenic Arabidopsis plants with or without the putative phosphorylation sites for SIG1 and demonstrated through in vivo labeling that Thr-170 was involved in the phosphorylation. We analyzed the in vivo and in vitro transcriptional responses of the transgenic Arabidopsis plants to the redox status in regard to involvement of the phosphorylation site. We revealed an enhanced phosphorylation of SIG1 under oxidative conditions of PQ in a form associated with the molecular mass of the holoenzyme. Phosphorylation of SIG1 proved crucial through a change in the promoter specificity for sustaining balanced expression of components in PS-I and PS-II and was responsible for harmonious electron flow to maintain photosynthetic efficiency.
光合作用电子传递的不平衡被认为是通过光合作用控制质体醌（PQ）的氧化还原状态来调节基因表达速率来纠正的，质体醌是一种连接电子载体。然后调整 PS 计量以提高光合作用效率。在原核生物中，σ 因子因其参与 RNA 聚合酶转录活性的控制而广为人知，而关于它们与氧化还原调节的关联尚无报道。我们发现，主要σ因子（SIG）SIG1 的磷酸化受氧化还原信号调节，并选择性地抑制编码 PS-I 蛋白的 psaA 基因的转录。我们产生了具有或不具有 SIG1 假定磷酸化位点的转基因拟南芥植物，并通过体内标记证明 Thr-170 参与了磷酸化。我们分析了转基因拟南芥植物在体内和体外对氧化还原状态的转录反应，以研究磷酸化位点的参与情况。我们发现，在 PQ 的氧化条件下，SIG1 以与全酶分子量相关的形式发生增强的磷酸化。通过改变启动子特异性来维持 PS-I 和 PS-II 组件的平衡表达，SIG1 的磷酸化被证明是至关重要的，这对于维持电子流以保持光合作用效率至关重要。
