高茶氨酸茶树新品系‘福黄2号’黄化变异机理

The albino mechanism of a new theanine-rich tea cultivar ‘Fuhuang 2’

摘要:

为了探讨茶树黄化变异和高茶氨酸形成机理，文中选用‘福云6号’和高茶氨酸茶树新品系‘福黄2号’为试验材料，利用超微电镜、广泛靶向代谢组学、靶向代谢组学和转录组学联合分析了茶树黄化变异的相关色素、代谢组及转录组数据。结果表明，通过靶向测定主要生化成分，共鉴定到5种儿茶素、可可碱和咖啡碱，以及20种游离氨基酸，包括茶氨酸、谷氨酰胺、精氨酸和谷氨酸等，其中，‘福黄2号’的氨基酸含量显著高于‘福云6号’，茶氨酸含量高达57.37 mg/g。叶片的超微结构显示，‘福黄2号’叶绿体细胞结构模糊，基粒片层大部分排列散乱、间隙大，类囊体呈丝状。色素测定显示，叶绿素a和叶绿素b、类胡萝卜素、类黄酮等色素含量显著下降，叶绿素酶（chlorophyllase，CLH）、9-顺式-环氧类胡萝卜素双加氧酶（9-cis-epoxycarotenoid dioxygenase，NCED）、类黄酮3β-羟化酶（flavonoid 3β-hydroxylase，F3H）和类黄酮3'，5'-羟化酶（flavonoid 3'，5'-hydroxylase，F3'5'H）等相关关键调控基因发生显著变化。与‘福云6号’相比，‘福黄2号’中共鉴定出138个差异代谢物（significantly changed metabolites，SCMs）和658个差异表达基因（differentially expressed genes，DEGs），KEGG富集分析表明，SCMs和DEGs显著富集到与氨基酸生物合成、谷胱甘肽代谢以及三羧酸循环等途径。‘福黄2号’黄化表型可能是光合作用蛋白、叶绿素代谢基因和叶绿素含量的缺乏所致。高茶氨酸的积累可能由于黄化叶中低氮消耗，以及碳骨架的缺乏，氨基和氮资源被更有效地储存，使得氨基酸合成通路中的代谢物及相关基因表达上调，茶氨酸成为黄化叶中显著积累的含氮化合物。

Abstract:

To explore the mechanism of tea albino variation and high theanine formation, ‘Fuyun 6’ and a new theanine-rich tea cultivar ‘Fuhuang 2’ were as materials in this study, pigment content, metabolome and transcriptome of the two cultivars were analyzed by ultramicroelectron microscopy, widely targeted metabolomics, targeted metabolomics and transcriptomics. The results showed that five catechins, theobromine, caffeine, and 20 free amino acids, including theanine, glutamine, arginine, etc., were identified by targeted metabolomics. The amino acid content of ‘Fuhuang 2’ was significantly higher than that of ‘Fuyun 6’, and the theanine content was as high as 57.37 mg/g in ‘Fuhuang 2’. The ultrastructure of leaves showed that the chloroplast cell structure of ‘Fuhuang 2’ was fuzzy, most of the grana lamellae were arranged in disorder, with large gaps, and the thylakoids were filiform. The determination of pigments showed that compared with ‘Fuyun 6’, the contents of chlorophyll A and B, carotenoids, flavonoids and other pigments of ‘Fuhuang 2’ decreased significantly, some important pigment-related-genes, such as chlorophyllase (CLH), 9-cis-epoxycarotenoid dioxygenase (NCED), flavonoid 3β-hydroxylase (F3H) and flavonoid 3', 5'-hydroxylase (F3'5'H) were significantly changed. Compared with ‘Fuyun 6’, ‘Fuhuang 2’ identified 138 significantly changed metabolites (SCMs) and 658 differentially expressed genes (DEGs). KEGG enrichment analysis showed that SCMs and DEGs were significantly enriched in amino acid biosynthesis, glutathione metabolism and TCA cycle. In general, the albino phenotype of ‘Fuhuang 2’ may be caused by a deficiency in photosynthetic proteins, chlorophyll metabolism genes and chlorophyll content. The accumulation of high theanine in ‘Fuhuang 2’ may be due to the low nitrogen consumption in yellowed leaves and the lack of carbon skeleton, amino and nitrogen resources are stored more effectively, resulting in the up regulation of metabolites and related gene expression in the amino acid synthesis pathway, theanine has become a significant accumulation of nitrogen-containing compounds in yellowed leaves.