Studies On Mechanism Of Cell Wall Pectin And Hemicellulose Invovlved In The Fluorine Accumulation In Tea Leaves

Tea is an important economic crop in China,which is closely related to the development of tea industry,and tea plants(camellia sinensis(L.)O.Kuntze),as hyper-accumulator of fluorine,in which leaves is an important part of fluorine accumulation.Therefore,the health of drinking tea has received much attention.Previous studies have shown that the cell wall polysaccharide component may play an important role in fluorine accumulation of tea leaves.In this study,the physiological changes in tea plants that treated with different concentrations of fluorine were analyzed.30 differentially expressed genes of PMEs(6)and XETs(24)were screened according to the previous transcriptomics,and q RT-PCR and ELISA technologies were used to analyze related genes,protein expression and enzyme activities,which reveal the molecular mechanism of cell wall polysaccharides components in fluorine accumulation and provide a theoretical basis for the mechanism of fluorine enrichment in cell wall of tea leaves.The main results are as follows:1.Under different fluorine concentrations,the stress resistance physiological indicators in tea plants were changed.The tea plants of Fudingdabai and Echa10 were treated with different fluorine concentrations of 0,0.2 and 0.5 mmol/l for 28 days.The results showed that the root activity increased significantly when the fluorine concentration was 0.2mmol/l,and decreased when the fluorine concentration was0.5mmol/l.The cell membrane permeability decreased significantly when the fluorine concentration was 0.2 mmol/l,and increased significantly when the fluorine concentration was 0.5mmol/l.The contents of proline and soluble sugar in tea leaves increased with the increasing of fluorine concentration,which indicated that the treatment of certain concentration of fluorine could promote the growth,while the treatment of high fluorine had an adverse effect on the growth of tea plants.2.Under fluorine treatment,the content of fluorine in cell wall and polysaccharide components were changed.The fluorine content of tea leaves that mainly distributed in the cell wall increased significantly,which was 7-10 times higher than that in roots.The fluorine was mainly distributed in the cell wall.The fluoride content in the cell wall was significantly increased,which respectively accounted for 50-60%,60-70% and 65-75%.The fluorine content of pectin and hemicellulose increased significantly,The ratio of fluorine content in pectin and hemicellulose to total fluorine content in cell wall of Fudingdabai was respectively about 50% and 32.7%,the ratio of fluorine content in pectin and hemicellulose to total fluorine content in cell wall of Echa10 was respectively about 51.7% and 38.8%,which indicates that pectin and hemicellulose may play an important role in the fluorine accumulation of tea plants.3.The effect of fluorine on the gene expression,protein content and activity of PMEs in tea plants were measured.The results of q RT-PCR showed that the expressions of PMEs in the leaves were increasing continuously,which increased to the maximum at48 h or 72 h.The results of ELISA showed that the changes of protein content and activity were basically consistent with the expression of genes,However,there was no obvious changes of expression of PMEs in roots,which was not consistent with protein content and activity.It is speculated that fluorine promotes the expression of PMEs activity in tea leaves,which decrease content of high methylester pectin and promotes the production of carboxyl.So fluorine may enhance content of fluorine in pectin by interaction with carboxyl.4.The expression of XETs gene,protein content and activity in tea plants under fluorine treatment were measured,the expression of XETs genes in leaves showed a decreasing trend,and both were lower than the expression level of 0h,the expression of protein content and activity were basically consisitent with their gene expression,which also showed a decreasing trend,however,there was no obvious change of expression of XETs in roots,which was not consistent with the expression of protein content and activity.This may be related to the relative content of xyloglucan and XTHs under F treatment.When the xyloglucan content in the Golgi is higher than XTHs,XTHs mainly exist in the cell wall in the form of a complex with xyloglucan.The cell wall becomes tight and inhibits the growth of the cells,and the rest of the xyloglucan increases the F content in the hemicellulose by forming a complex with F in tea leaves.