Research In Organic Acids And Cell Wall Pectin Methylesteration Involved In Aluminum Resistance/Toxicity In Tea Plant [Camellia Sinensis(L.) Kuntze] Roots

In recent years,more and more serious problems of soil acidification in tea garden appear,as a consequence of high levels of activated aluminum(Al)by soil acidification,which cannot be ignored.Therefore,it is important that Al resistance/detoxication was investigated in tea plant.On the one hand,it can be further understanding of Al.in the physiological and biochemical changes in the tea plant organs for servicing to the development of tea production in China.On the other hand,it provides an important theoretical support for cultivating new varieties.Two-year-old rooted cuttings of tea cv.Longjing-changye were used with Al treatment(0,0.1,0.4,2,or 4 mM)to measure elongation and activities in roots and protein,chlorophyll and MDA contents,physiological characterization(SOD,POD and CAT activities)in tea plant leaves to investigate the mechanism of Al resistance/detoxication.With the increased Al,the elongation and activities in roots and protein,chlorophyll and MDA contents,physiological characterization(SOD,POD,and CAT activities)in tea plant leaves was increased,and then decreased at last.The results suggest that low concentration of Al can promote growth of tea plants and high level of Al inhibit growth of tea plants foreshadowing to investigate the mechanism of aluminum resistance/detoxication in tea plant.To determine whether Al was eliminated in root apex by Al-induced secretion of organic acids,organic acids exudated in the root were quantified in vivo,The data showed that organic acids of root exudes,including oxalate,glycolic acid,eitrate and malate increased following increased Al concentration,as well as increased in roots.The activities of GO,MDH and CS and the levels of their genes expression were the same trend of their contents.These results indicated that the content of organic acids of root exudes and roots were susceptible by their related enzymes regulated by relevant genes of these enzymes.These may be the reason of Al resistance/detoxication in tea plant.Compared with other tussues,Al content in roots were highest in tea plant tissues after AI treatments.With increasing Al concentration,the proportion of Al in the root tip cell wall increased,as well as Al distribution in the root tip,which can be observed using the hematoxyl in staining and microtechnic.And decreasing methyl-ester pectin containing increasing low-methyl-ester pectin and decreasing high-methyl-ester pectin,which was detected the method of immunofluorescence localization of pectin using two kinds of antibodies LM19 and LM20,and increasing expression of CsPME genes were observed with increasing Al concenttration.These results show that root cell wall is an important part for Al resistance/detoxication in tea plant,and the pectin methyl-ester regulated by CsPME genes plays an important role in cell wall extension to response the Al resistance/detoxication.In conclusion,organic acids and cell wall pectin methylesteration are involved in Al resistance/detoxication in tea plant.With increasing Al concentration,Al stimulates the relevant genes of organic acids,which is regulate enzymes to increase the content of organic acids of root exudes and organic acids in roots,and the CsPME family genes,which is regulate PME activities to transform high-methyl-ester pectin into low-methyl-ester pectin,involving in Aluminum resistance/detoxication in tea plant.