Influence Of Light On Catechins Biosynthesis In Tea Plant

The content of tea polyphenols and catechins is an important indicator of the quality of tea. Catechins are derived from the phenylpropanoid biosynthetic pathways and flavoniods synthesis pathway with a dozen of enzymes involving in. Studies had shown that light could affect the content of tea polyphenols and catechins in tea plant. Most of the genes responsible for catechins biosynthesis in tea have been cloned so far.To further elucidate the impacts of different light intensity and quality on tea polyphenols and each component of catechins, this study discussed from two aspects including different light intensity and quality obtained by shade nets and transparent plastic films covered with different colors.On the one hand, total polyphenols and six kinds of catechins including C, EC EGC, EGCG, GCG, ECG in one bud and one leaf of tea plant were analyzed by UV spectrophotometry and high-performance liquid chromatography(HPLC); on the other hand, by utilizing RT-PCR technique,we dectected the expression level of 12 genes related to catechins biosynthesis, such as PAL, C4 H,CHS. Main research results are as follows:The light intensity can affect content of total polyphenols and each component of catechins. The accumulation of tea polyphenols benefited from the increase of light intensity. But tea plant responded to different low light intensity are related to varieties and development period.The compositions of catechins responded differently to light intensity. C, GCG had no obvious response to low light intensity. But low light intensity can inhibit synthesis of other catechins and reduce the content of total catechins. Non-galloylated catechins EGC and EC were more influenced by low light intensity. Besides the weaker the light intensity, the lower the content of EGCG, total catechins in 1B1 L and EC, total catechins in 1B3 L.Polyphenols can be reduced in particular developmental stages by red, purple and blue light. The trends of yellow light were not pronouncedEC、EGC、ECG content was decreased during three stages under red light treatment, but the rest components had no obvious response to red light. Purple and yellow light only had inhibitory effect on ECG in some degree. The amount of EGC, EC, ECG and total catechins decreased under blue light and the content of GCG and EGCG also decreased in new shoots at early developing stages but C is not obvious changed.Most catechin-related genes were affected by light intensity. But genes had different response modes. The lower light intensity was, the more genes were affected and genes responded also sooner. The gene expression of CHI, F3 H and ANR remarkably increased in 1B2 L but ANS was significantly decreased in 1B3 L under SN treatment. Under DN treatment PAL and ANR were up-regulated in 1B1 L and F3 H was increased at 1B1 L and 1B2 L, but F3’5’H, ANS and ANR down-regulated in 1B3 L.Different wavelengths of visible light have different effects on genes associated with catechins biosynthesis. Red light promoted expressions of C4 H F3’H and ANS in 1B1 L. F3’H was promoted in 1B2 L. Purple light enhanced the expression of ANS gene in 1B1 L. F3 H and F3’H were promoted and F3’5’H was inhibited at the second stage. Purple light increased expressions of C4 H and F3 H in 1B3 L.Yellow light inhibited F3 H expression in 1B1 L.In 1B2 L Yellow light promote the expressions of F3’H and F3 H but decreased expression of F3’5’H. Blue light promote the expression of F3 H and F3’H in the second period and increased expression of F3’H but suppressed ANS in 1B3 L.