黄金芽’是光照敏感型黄化茶树品种—强光下新稍黄色、弱光下新稍绿色。目前对于其受光照强度诱导的叶片颜色变化机制还不清楚。在本研究中，作者以四年生的‘黄金芽’茶树品种为材料，设置两个处理，即自然光照处理（Y）和遮阳80%处理（Y+S），处理七天后分别对两个处理的材料的芽下第二叶进行取样，一部分进行叶片中叶绿素和类胡萝卜素含量的测定，一部分进行代谢组分检测，还有一部分进行iTRAQ/LC–MS/MS差异蛋白分析。结果显示遮阳处理下比光照下叶片中叶绿素a和b的含量分别提高5倍和4倍以上、类胡萝卜素含量提高将近2倍；对二者中叶绿素合成途径、类胡萝卜素合成途径、叶绿体光合系统等的关键基因、蛋白表达以及代谢组分分析表明‘黄金芽’在光照下叶片黄化主要是因为叶片中类囊体膜结构的缺失抑制了叶绿素的合成，其阻断位点位于叶绿体基质向类囊体膜的叶绿素合成过渡阶段，并且叶绿素降解的增加进一步导致叶绿素含量的减少；此外，光合系统相关蛋白的减少以及光合电子转移的受阻也导致了光照下‘黄金芽’叶片的光和效率，同时，光照下黄化叶片的叶黄素循环以及光系统循环电子运输的增强提高了黄化叶片的耐光性。

Abstract

‘Huangjinya’ (HJY) is a light-sensitive chlorotic tea cultivar (Camellia sinensis L.) that grows chlorotic shoots under sun-light conditions but its chlorotic shoots turn green under weak light conditions. However, the mechanisms responsible for light intensity-induced changes in leaf color remain unclear. In this study, we compared HJY plants with chlorotic leaves exposed to sun-light (Y) and HJY plants with green leaves exposed to both sun and shade (Y + S) on the basis of metabolite profiles, expression of proteins and genes in the pigment metabolic pathway and photosynthetic system. Our results showed that inhibition of chlorophyll synthesis and enhancement of chlorophyll degradation were the reasons for the decrease of chlorophyll content in Y. And the blocked sites were located in the transition stage of chlorophyll synthesis from chloroplast stroma to thylakoid membrane, i.e. from COPPIII to PPIX. In addition, the decrease of photosynthetic system-related proteins and the obstruction of photosynthetic electron transport in Y resulted in the decrease of photosynthetic efficiency. The tolerance of chlorotic leaves to sun-light conditions was enhanced by strengthening xanthophyll cycle and cyclic electron transport. Altogether, this study provides a better understanding of the mechanisms responsible for the chlorotic phenotype.