Yue Cuinan, Wang Zhihui, Yang Puxiang
Jiangxi Sericulture and Tea Research Institute, Nanchang, 330043, China.
Jiangxi Key Laboratory of Tea Quality and Safety Control, Nanchang, 330203, China.
Bot Stud. 2021 Dec 11;62(1):21. doi: 10.1186/s40529-021-00329-2.
Light is the ultimate energy source of plant photosynthesis, which has an important impact on the growth, development, physiology and biochemistry of tea plant. Photosensitive etiolated tea plant belongs to a kind of colored leaf plant, which is a physiological response to light intensity. Compared with conventional green bud and leaf of tea plant, the accumulation of pigment compounds (chlorophyll and carotenoids, etc.) closely related to a series of reactions of photosynthesis in photosensitive etiolated tea plant is reduced, resulting in the difference of leaf color of tea. This specific tea resource has high application value, among which high amino acid is one of its advantages. It can be used to process high-quality green tea with delicious taste and attractive aroma, which has been widely attention. The mechanism of the color presentation of the etiolated mutant tea leaves has been given a high topic and attention, especially, what changes have taken place in the pigment compounds of tea leaves caused by light, which makes the leaves so yellow. At present, there have been a lot of research and reports.
We describe the metabolism and differential accumulation of key pigment compounds affecting the leaf color of photosensitive etiolated tea that are triggered by light, and discuss the different metabolism and key regulatory sites of these pigments in different light environments in order to understand the "discoloration" matrix and mechanism of etiolated tea resources, answer the scientific question between leaf color and light. It provides an important strategy for artificial intervention of discoloration of colored tea plant.
The differential accumulation of pigment compounds in tea plant can be induced phytochrome in response to the change of light signal. The synthesis of chlorophyll in photoetiolated tea plants is hindered by strong light, among which, the sites regulated by coproporphyrinogen III oxidase and chlorophyllide a oxidase is sensitive to light and can be inhibited by strong light, resulting in the aggravation of leaf etiolation. The phenomenon can be disappeared or weakened by shading or reducing light intensity, and the leaf color is greenish, but the increase of chlorophyll-b accumulation is more than that of chlorophyll-a. The synthesis of carotenoids is inhibited strong light, and high the accumulation of carotenoids is reduced by shading. Most of the genes regulating carotenoids are up-regulated by moderate shading and down-regulated by excessive shading. Therefore, the accumulation of these two types of pigments in photosensitive etiolated tea plants is closely related to the light environment, and the leaf color phenotype shape of photosensitive etiolated tea plants can be changed by different light conditions, which provides an important strategy for the production and management of tea plant.
光是植物光合作用的最终能量来源，对茶树的生长、发育、生理生化过程具有重要影响。光敏黄化茶树属于彩叶植物的一种，是对光照强度的一种生理响应。与常规的茶树绿色芽叶相比，光敏黄化茶树中与光合作用一系列反应密切相关的色素化合物（叶绿素、类胡萝卜素等）积累减少，导致茶叶叶色出现差异。这种特异的茶树种质资源具有较高的应用价值，其中高氨基酸含量是其优势之一。它可用于加工口感鲜美、香气诱人的优质绿茶，受到广泛关注。黄化突变体茶叶的呈色机制一直是热门话题并备受关注，尤其是光导致茶叶色素化合物发生了哪些变化，使得叶片如此发黄。目前已有诸多研究报道。
阐述光触发的影响光敏黄化茶树叶色的关键色素化合物的代谢及差异积累，探讨这些色素在不同光照环境下的不同代谢情况及关键调控位点，以了解黄化茶树种质资源的“变色”基质及机制，解答叶色与光照之间的科学问题。为彩叶茶树变色的人工干预提供重要策略。
茶树色素化合物的差异积累可由光敏色素响应光信号变化诱导产生。强光会阻碍光黄化茶树中叶绿素的合成，其中，原卟啉原III氧化酶和叶绿素酸酯a氧化酶调控的位点对光敏感，会被强光抑制，导致叶片黄化加剧。通过遮光或降低光照强度，该现象可消失或减弱，叶片呈绿色，但叶绿素b积累量的增加幅度大于叶绿素a。强光会抑制类胡萝卜素的合成，遮光会使类胡萝卜素积累量降低。多数调控类胡萝卜素的基因在适度遮光下上调表达，在过度遮光下下调表达。因此，这两类色素在光敏黄化茶树中的积累与光照环境密切相关，不同光照条件可改变光敏黄化茶树叶色表型形态，为茶树生产管理提供重要策略。
