Study On The Mechanism Of Summer Tieguanyin Tea’s(Camellia Sinensis(L·)O.Kuntze) Quality Under Different Shading Conditions

Tea,one of Chinese traditional drink,is also commonly used as a traditional Chinese medicine(TCM).To date,the main medicinal ingredients extracted from tea leaves are known to have the ability to regulate blood lipid,resist atherosclerosis and the lipid peroxidation,enhance the immune function and inhibit tumor development.Anxi county has the LARgest production of Oolong tea in China.Anxi Tieguanyin tea(Camellia sinensis(L.)O.Kuntze)is generally harvested four times a year,according to the harvest season each harvested tea is named as spring tea,summer tea,mid-summer tea and fall tea,respectively.Summer tea has the highest yield with low quality,in turn this limit the tea producing in China.In this paper,five-year old Tieguanyin tea plants(Camellia sinensis(L.)O.Kuntze)was employed as materials,the physiological,RT-PCR and proteomics methods were applied to analyze the change of tea quality,the expressing level of the key genes related to the synthesis of Catechins and differential proteins under different shading treatments The following results were gotten.1.Chlorophyll a and chlorophyll b content in the leaf of tea plants under shading treatment in the summer-tea growing period increased and the ratio of chlorophyll a/b decreased,indicating that shading treatment was beneficial for summer tea to improve photosynthetic efficiency.2.Superoxide dismutase(SOD)activity and malondialdehyde(MDA)content in the leaf of tea plants under shading treatments significantly decreased,indicating that shading was helpful for the tea tree to avoid high light stress.3.HPLC result showed that the affeine and non ester catechins content in the leaf of tea plants under shading reduced,while free amino acids,ester catechins and and total catechins content increased significantly.This result implied that shading was not only beneficial to reduce the content of substances affecting tea taste,but also conducive to the accumulation of some active substances.4.RT-PCR results indicated that shading significantly lowered the expression of the genes LAR,CHS,F3H,DFR and F3’5’H except ANR in the leaf of tea plants,which were related to catechins synthesis pathwayLAR.These genes were down-regulated to inhibit the synthesis of catechins,especially non ester catechins.But the down-regulation of these catechin-related genes might have nothing to do with the accumulation of ester type catechins..5.In the leaf of tea plants under shading treatments,some proteins related with antioxidant,energy metabolism,cell motility,amino acid metabolism and photosynthesis were differentially expressed,10 of which were up-regulated,such as ribulose-1,5-bisphosphate carboxylase/oxygenase,chaperonin 60 subunit beta 2,oxygenase activase B,etc.And 4 of them were down-regulated,such as superoxide dismutase,s-adenosylmethionine synthetase,etc.This results were consistence with the finding in physiological experiment.In conclusion,shading promise to the photosynthesis of tea plants,weaken the antioxidant system and reduce the content of substances which were related to the tea flavor.