Quality Constituents And Albinism Analysis In The Young Leaves Of Albino Tea Cultivars

Under certain environment, leaves of some tea varieties become bleaching and their amino acid contents increase obviously compared to common green leaves. This kind of tea cultivars are quite precious because they are rare, tasteful and healthy. However, studies on genetic background and characteristic compounds and their biosynthesis mechanism of albino tea cultivars are seldom reported. In this study, SSR markers were employed for analysis of the difference of genetic background of four albino tea cultivars. The key quality compounds (free amino acids, catechins, caffeine) and pigment compounds (carotenoids and chlorophylls) were quantitatively and qualitatively determined using high performance liquid chromatography (HPLC). Moreover, the data were further analyzed using multivariate analysis approaches to reveal key genes and key enzymes responsible for terpenoid pigment biosynthesis. In addition, correlation between metabolite and gene expression profiles was analyzed to learn the molecular mechanisms of leaf albinism, thus for improving the yield and quality of albino tea.The results of this study showed that, the genetic background similarity between ’Tiantai huangcha’ and ’Huangjinya’,’Anji baicha’and’Yujinxiang’reached the maximum 0.7, while between’Tiantai huangcha’and’Yujinxiang’,’Huangjinya’and ’Yujinxiang’were only 0.4. Our results indicated that the four albino tea cultivars had different genetic background. Expression of genes such as CRTISO, PDS, VDE-1, VDE-2 and ZEP in terpenoid pathways changed significantly in the albino cultivar ’Yujinxiang’ compared to control cultivar ’Nongkangzao’. However, the expression of the genes in MVA and MEP pathways did not change in the albino and control cultivars except for HMGS and HDS, which were strongly expressed in’Yujinxiang’ relative to control cultivar. What is more, why gene IDI were strongly expressed in albino variety also need further discussion.Our results suggest that in albnio tea cultivars, high level of amino acids (especially theanine and glutamic acid), along with low levels of catechins and caffeine, contribute to the qualities of albino tea, which include reduced astringency and bitterness, along with a strong umami taste. Whereas increases were noted in the Chi a/b ratio and the contents of both zeaxanthin, we speculated that increased levels of Chl a/b ratio and zeaxanthin in albino leaves would be one of the adaptive responses to photooxidative stress for maintaining photosynthetic efficiency and capacity. Multivariate analysis identified EGCG and carotenoids (Lutein, β-Carotene) as the most important contributors to the metabolic profile variance between the albino and green tea cultivars. Catechins, carotenoids, caffeine and amino acids have the greatest contribution for the classification from metabolic level. We speculate that in the albino tea, inhibited of chlorophyll, carotenoid and caffeine synthesis dynamic promoted amino acid synthesis pathway.