Mulo Paula, Sakurai Isamu, Aro Eva-Mari
Department of Biochemistry and Food Chemistry, University of Turku, Finland.
Biochim Biophys Acta. 2012 Jan;1817(1):247-57. doi: 10.1016/j.bbabio.2011.04.011. Epub 2011 May 2.
The Photosystem (PS) II of cyanobacteria, green algae and higher plants is prone to light-induced inactivation, the D1 protein being the primary target of such damage. As a consequence, the D1 protein, encoded by the psbA gene, is degraded and re-synthesized in a multistep process called PSII repair cycle. In cyanobacteria, a small gene family codes for the various, functionally distinct D1 isoforms. In these organisms, the regulation of the psbA gene expression occurs mainly at the level of transcription, but the expression is fine-tuned by regulation of translation elongation. In plants and green algae, the D1 protein is encoded by a single psbA gene located in the chloroplast genome. In chloroplasts of Chlamydomonas reinhardtii the psbA gene expression is strongly regulated by mRNA processing, and particularly at the level of translation initiation. In chloroplasts of higher plants, translation elongation is the prevalent mechanism for regulation of the psbA gene expression. The pre-existing pool of psbA transcripts forms translation initiation complexes in plant chloroplasts even in darkness, while the D1 synthesis can be completed only in the light. Replacement of damaged D1 protein requires also the assistance by a number of auxiliary proteins, which are encoded by the nuclear genome in green algae and higher plants. Nevertheless, many of these chaperones are conserved between prokaryotes and eukaryotes. Here, we describe the specific features and fundamental differences of the psbA gene expression and the regeneration of the PSII reaction center protein D1 in cyanobacteria, green algae and higher plants. This article is part of a Special Issue entitled Photosystem II.
蓝细菌、绿藻和高等植物的光系统（PS）II容易受到光诱导的失活影响，D1蛋白是这种损伤的主要靶点。因此，由psbA基因编码的D1蛋白在一个称为PSII修复循环的多步骤过程中被降解并重新合成。在蓝细菌中，一个小基因家族编码各种功能不同的D1同工型。在这些生物体中，psbA基因表达的调控主要发生在转录水平，但通过翻译延伸的调控对表达进行微调。在植物和绿藻中，D1蛋白由位于叶绿体基因组中的单个psbA基因编码。在莱茵衣藻的叶绿体中，psbA基因表达受到mRNA加工的强烈调控，特别是在翻译起始水平。在高等植物的叶绿体中，翻译延伸是psbA基因表达调控的普遍机制。即使在黑暗中，植物叶绿体中预先存在的psbA转录本池也会形成翻译起始复合物，而D1的合成只能在光照下完成。受损D1蛋白的替换还需要许多辅助蛋白的协助，这些辅助蛋白在绿藻和高等植物中由核基因组编码。然而，这些伴侣蛋白中的许多在原核生物和真核生物之间是保守的。在这里，我们描述了蓝细菌、绿藻和高等植物中psbA基因表达的具体特征和根本差异以及PSII反应中心蛋白D1的再生。本文是名为“光系统II”的特刊的一部分。
