School of Life Science & Technology, Tokyo Institute of Technology, Yokohama, 226-8501 Japan.
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, 113-0033 Japan.
Plant Cell Physiol. 2019 Dec 1;60(12):2660-2671. doi: 10.1093/pcp/pcz203.
Plants convert solar energy into chemical energy through photosynthesis, which supports almost all life activities on earth. Because the intensity and quality of sunlight can change dramatically throughout the day, various regulatory mechanisms help plants adjust their photosynthetic output accordingly, including the regulation of light energy accumulation to prevent the generation of damaging reactive oxygen species. Non-photochemical quenching (NPQ) is a regulatory mechanism that dissipates excess light energy, but how it is regulated is not fully elucidated. In this study, we report a new NPQ-regulatory protein named Day-Length-dependent Delayed-Greening1 (DLDG1). The Arabidopsis DLDG1 associates with the chloroplast envelope membrane, and the dldg1 mutant had a large NPQ value compared with wild type. The mutant also had a pale-green phenotype in developing leaves but only under continuous light; this phenotype was not observed when dldg1 was cultured in the dark for ≥8 h/d. DLDG1 is a homolog of the plasma membrane-localizing cyanobacterial proton-extrusion-protein A that is required for light-induced H+ extrusion and also shows similarity in its amino-acid sequence to that of Ycf10 encoded in the plastid genome. Arabidopsis DLDG1 enhances the growth-retardation phenotype of the Escherichia coli K+/H+ antiporter mutant, and the everted membrane vesicles of the E. coli expressing DLDG1 show the K+/H+ antiport activity. Our findings suggest that DLDG1 functionally interacts with Ycf10 to control H+ homeostasis in chloroplasts, which is important for the light-acclimation response, by optimizing the extent of NPQ.
植物通过光合作用将太阳能转化为化学能，为地球上几乎所有的生命活动提供支持。由于阳光的强度和质量在一天中会发生剧烈变化，因此各种调节机制有助于植物相应地调节其光合作用输出，包括调节光能积累以防止产生有害的活性氧物种。非光化学猝灭（NPQ）是一种调节机制，可耗散多余的光能，但它是如何被调节的还不完全清楚。在本研究中，我们报告了一种名为光周期依赖性延迟绿化 1（DLDG1）的新的 NPQ 调节蛋白。拟南芥 DLDG1 与叶绿体被膜结合，与野生型相比，dldg1 突变体具有较大的 NPQ 值。该突变体在发育中的叶片中也表现出浅绿色表型，但仅在连续光照下观察到；当 dldg1 在黑暗中培养≥8 小时/天时，不会观察到这种表型。DLDG1 是一种质体膜定位的蓝细菌质子外排蛋白 A 的同源物，该蛋白对于光诱导的 H+外排是必需的，并且其氨基酸序列与质体基因组编码的 Ycf10 也有相似性。拟南芥 DLDG1 增强了大肠杆菌 K+/H+反向转运蛋白突变体的生长迟缓表型，并且表达 DLDG1 的大肠杆菌的外翻膜囊泡显示出 K+/H+反向转运活性。我们的研究结果表明，DLDG1 与 Ycf10 功能相互作用，通过优化 NPQ 的程度来控制叶绿体中的 H+稳态，这对于光适应反应很重要。
