Thum K E, Kim M, Christopher D A, Mullet J E
Department of Biochemistry and Biophysics, Texas A & M University, College Station, Texas 77843, USA.
Plant Cell. 2001 Dec;13(12):2747-60. doi: 10.1105/tpc.010345.
The reaction center core of photosystem II is composed of two chlorophyll binding proteins, D1 and D2, that are encoded by the chloroplast genes psbA and psbD. These chlorophyll binding proteins are damaged during photochemistry, especially under high irradiance. Photosystem II function is maintained under these conditions through turnover and resynthesis of D1 and D2. Blue light-activated transcription of psbD from a special light-responsive promoter is part of the repair system. In this study, light-activated chloroplast and psbD transcription were studied after dark adaptation of 21-day-old light-grown Arabidopsis plants. Illumination of dark-adapted plants with red light increased chloroplast transcription activity and transcription from the psbD light-responsive promoter. Blue light further increased chloroplast transcription activity and stimulated differential transcription from the psbD light-responsive promoter. Photoreceptor mutants showed that blue light-specific activation of chloroplast transcription and the psbD light-responsive promoter involve cryptochrome 1 (cry1) or cryptochrome 2 (cry2) and phytochrome A (phyA). Blue light-induced activation of the psbD light-responsive promoter was normal in det2-1 and hy5-1 but attenuated in det3-1. Therefore, cry1/cry2/phyA-mediated blue light activation of the psbD light-responsive promoter in 21-day-old Arabidopsis plants does not involve hy5, a transcription factor that mediates other phyA and blue light-induced responses.
光系统II的反应中心核心由两个叶绿素结合蛋白D1和D2组成，它们由叶绿体基因psbA和psbD编码。这些叶绿素结合蛋白在光化学过程中会受到损伤，尤其是在高光照强度下。在这些条件下，通过D1和D2的周转和重新合成来维持光系统II的功能。从一个特殊的光响应启动子对psbD进行蓝光激活转录是修复系统的一部分。在本研究中，对21日龄光照培养的拟南芥植株进行暗适应后，研究了光激活的叶绿体和psbD转录。用红光照射暗适应的植株会增加叶绿体转录活性以及从psbD光响应启动子的转录。蓝光进一步增加叶绿体转录活性，并刺激从psbD光响应启动子的差异转录。光受体突变体表明，叶绿体转录和psbD光响应启动子的蓝光特异性激活涉及隐花色素1（cry1）或隐花色素2（cry2）以及光敏色素A（phyA）。蓝光诱导的psbD光响应启动子激活在det2 - 1和hy5 - 1中正常，但在det3 - 1中减弱。因此，在21日龄拟南芥植株中，cry1/cry2/phyA介导的psbD光响应启动子的蓝光激活不涉及hy5，hy5是一种介导其他phyA和蓝光诱导反应的转录因子。
