Research On The Function Of CsMESs Involved In The Chlorophyll Degradation Of Photosensitive Tea Plant ’Huang Kui’

Tea tree(Camellia sinensis(L.)O.Ktze)is a perennial evergreen woody plant belonging to the subtropical zone.During its growth and development,their leaf color can be yellow or white.In this context,some yellowed varieties were screened out,such as the ‘Huangjinya’ and ‘Huangkui’.Due to their unique and fresh taste,such tea products are selling well in the market.The molecular mechanism of plant yellowing or albino is far from perfect,and the regulatory genes of chlorophyll destruction,chloroplast disintegration,and photosynthetic system destruction are still unknown.‘Huangkui’,a yellow tea variety,has different leaf colors after germination,and we named it ‘G’,‘Y’ and ‘W’ according to the leaf color.It can be used as an excellent material for studying the yellowing mechanism of tea tree.In this paper,the differences of ‘Huangkui’ in pigment,chlorophyll fluorescence and chloroplast ultrastructure were explored.Through the analysis of transcriptome data,three candidate genes,Cs MES1,Cs MES2 and Cs MES3,which may be related to leaf color,were screened.The enzyme kinetics and gene function were discussed,which provided a theoretical basis for the development and utilization of high-quality tea plant varieties and the function research of chlorophyll degradation regulators in etiolated tea plants.The main results of gene function analysis are as follows:1.This paper firstly analyzed the pigment,chloroplast fluorescence and chloroplast ultrastructure of ‘Huangkui’ seedlings.It was found that the difference in leaf color of‘Huangkui’ was closely related to the pigment content and the completeness of chloroplast structure development.2.This paper also explored the response of ‘Huangkui’ seedlings(G,Y,W)to light through shading and high-light treatments.It was found that shading turned the color of ‘Y’ leaves green and made the contents of chlorophyll a and chlorophyll b increased,however,‘G’ and ‘W’ were not affected.Moreover,high light treatment will make the leaves of ‘G’ and ‘Y’ lighter,the pigment content will be reduced,and ‘W’ will die.That is,the lighter the leaf color,the stronger the sensitivity to light response.3.By qRT-PCR technology,the expression of Cs MESs in different varieties and tissues of tea plant,and the expression of tea plant under salt,Me JA,drought,cold and high light stress were detected.Experiments found that only the expression of Cs MES1 was consistently higher in plants with lighter leaves;The three Cs MESs were highly expressed in more mature tissues and organs,no matter in ‘Shuchazao’ or ‘Huangkui’.Taken together,we speculate that Cs MES1 is most likely involved in chlorophyll degradation.And the three Cs MESs may accelerate the degradation of chlorophyll under the stress of salt,Me JA,drought and cold.4.Through the study of the function of Cs MESs genes in tea plant,it was found that Cs MESs proteins are located in the cytoplasm;Cs MES1 protein can hydrolyze both pheophorbide a and Me IAA;The leaves of Cs MES1 overexpressed Arabidopsis thaliana have lighter color and low chlorophyll a content;When exogenously applied with Me IAA,the root length were shorter compared to the control;and when it was grown on the medium with Me JA,the amount of lateral roots were significantly increased compared to the control.It is indicated that Cs MES1 can participate in the chlorophyll degradation pathway,can also hydrolyze Me IAA,and can affect plant leaf color,pigment and growth.