膜质代谢变化在‘白鸡冠’茶树叶片白化中的作用机制研究

Camellia Sinensis cv. Baijiguan has a considerable economic value due to its special albino phenotype and unique characteristics of tea quality. It`s also one of the most important and scarce tea germplasm resources in Fujian Province. As a kind of tea germplasm which albino bud and leaf can be inherited stably, Baijiguan is also a good material for tea variety innovation and breeding. This project carries out the research in Baijiguan about membrane lipid metabolic pathways and key genes related to chloroplast development based on lipidomics and transcriptomics. To analyze the changes of leaf lipid metabolism before and after shading conditions in Baijiguan, and detect leaf membrane lipid composition in albino tea plant, and prove lipid metabolic pathways in this study. The expression of key genes related to leaf membrane lipid metabolic pathways and chloroplast development will be identified to clear the key enzyme genes involved in membrane lipid metabolic pathways in albino tea plants. This research can provide scientific support to reveal the physiological and genetic molecular regulatory mechanism in albino leaf character of Camellia Sinensis cv. Baijiguan deeply and systemically, and have a great significance for the scientific appraisal and utilization of the important and scarce tea germplasm resources in Fujian Province，and these also have an important guiding role for the research about tea breeding innovation and utilization and tea product innovation in future.

‘白鸡冠’茶树因其特异性白化性状和独具特色的茶叶品质特征而颇具经济价值，也是福建省优异、珍稀的重要茶树种质资源之一。作为一种可稳定遗传的茶树白化芽叶种质，‘白鸡冠’茶树也是品种创新和育种的良好材料。本项目基于脂质组学和转录组学开展白鸡冠茶树新梢白化膜脂类代谢途径及叶绿体发育关键基因的研究，分析遮荫前后及遮荫条件下‘白鸡冠’茶树叶片的脂类代谢变化，探明茶树白化叶片的膜脂组成、脂质代谢途径，通过研究茶树白化叶片膜脂类代谢途径及叶绿体发育关键基因的表达，明确参与白化茶树膜脂类代谢途径的关键酶基因。本研究为深入和系统的揭示白鸡冠茶树叶片白化性状的生理和遗传调控机制提供科学支撑，对科学鉴定和利用福建优异珍稀茶树种质资源具有重要意义，也对今后在茶树育种创新利用研究领域和茶叶产品开发创新具有重要的指导作用。

‘白鸡冠’茶树是武夷山“四大名丛”之一，自发现并利用至今已有三百余年的历史，以其新梢芽叶的典型白化性状而得名并为人熟知。本研究先鉴定并明确其芽叶白化类型为光照敏感型白化茶树，再结合田间实验开展茶树的的不同光照处理，测定不同光强处理白鸡冠茶树叶片叶绿素SPAD值、SOD、POD、 CAT酶活性，结果显示白鸡冠能够积极响应光照调控而表现自我防御性状变化，其防御酶活性普遍高于肉桂，响应光照调控变化显著，酶活性与叶色变化相关。.采用脂质组学技术对白鸡冠新梢第二叶的脂质成分进行了检测，共检测出156种极性脂，结果表明绿叶对照茶树品种肉桂在所有处理下脂质含量无显著差异，白鸡冠茶树在正常光照下以及遮阴处理恢复光照后，MGDG/DGDG较对照低，膜脂/叶绿素比值较对照啊高，导致类囊体膜不完整，叶绿素减少，叶色白化。遮荫后MGDG、DGDG和PG等参与类囊体膜重建的脂质，含量显著降低；表明光照通过影响白鸡冠的膜脂组成而影响叶色。.本研究还构建了与光敏型白化茶树白鸡冠第二叶在遮荫和恢复光照条件下出现的复绿与白化表型相关联的共表达基因网络，得到15个与复绿和白化密切相关的基因模块，从中筛选出了4个基因（CSS0019351、CSS0045917、CSS0031492、CSS0036305）和3个转录因子（CSS0046793、CSS0018417、CSS0023211），发现其基因功能与拟南芥等植物中已报道的叶绿体形成和叶绿素合成通路紧密相关。对相关基因进行荧光定量表达验证，发现不遮荫的白化叶和恢复光照后的叶片中膜脂合成基因PLD、plc、DGK、MGD和DGD的表达下降，使膜脂含量降低，膜结构不稳定，导致叶绿素降解基因CLH、SGR、PPH、PAO和RCCR表达上升，降解加速，叶色白化；遮荫后膜脂合成基因表达升高，膜结构重建，叶绿素降解基因表达降低，叶色转绿，说明白鸡冠白化期叶绿素降解加速导致叶片白化，且该过程是一个可逆反应。克隆获得白鸡冠茶树CsPPH基因（NCBI登录号：MK359094）和3条CsCLHs基因cDNA全长序列，进一步研究表明CsCLHs在白化叶中高表达。