Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama, Japan.
Department of Molecular Microbiology, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo, Japan.
Plant Cell Physiol. 2019 Feb 1;60(2):367-375. doi: 10.1093/pcp/pcy218.
Orange carotenoid protein (OCP) plays a vital role in the thermal dissipation of excitation energy in the photosynthetic machinery of the cyanobacterium Synechocystis sp. PCC 6803. To clarify the role of OCP in the protection of PSII from strong light, we generated an OCP-overexpressing strain of Synechocystis and examined the effects of overexpression on the photoinhibition of PSII. In OCP-overexpressing cells, thermal dissipation of energy was enhanced and the extent of photoinhibition of PSII was reduced. However, photodamage to PSII, as monitored in the presence of lincomycin, was unaffected, suggesting that overexpressed OCP protects the repair of PSII. Furthermore, the synthesis de novo of proteins in thylakoid membranes, such as the D1 protein which is required for the repair of PSII, was enhanced in OCP-overexpressing cells under strong light, while the production of singlet oxygen was suppressed. Thus, the enhanced thermal dissipation of energy via overexpressed OCP might support the repair of PSII by protecting protein synthesis from oxidative damage by singlet oxygen under strong light, with the resultant mitigation of photoinhibition of PSII.
橙色类胡萝卜素蛋白 (OCP) 在蓝藻集胞藻 PCC 6803 的光合作用机器中发挥着重要作用，可消散激发态能量。为了阐明 OCP 在保护 PSII 免受强光方面的作用，我们构建了 OCP 过表达的集胞藻突变株，并研究了 OCP 过表达对 PSII 光抑制的影响。在 OCP 过表达的细胞中，能量的热耗散增强，PSII 的光抑制程度降低。然而，在林可霉素存在下监测到的 PSII 光损伤不受影响，表明过表达的 OCP 保护 PSII 的修复。此外，在强光下，OCP 过表达的类囊体膜中新合成的蛋白质，如修复 PSII 所必需的 D1 蛋白，增强，而单线态氧的产生受到抑制。因此，通过过表达 OCP 增强的能量热耗散可能通过保护蛋白质合成免受单线态氧的氧化损伤来支持 PSII 的修复，从而减轻 PSII 的光抑制。
