| Tea is the three most popular nonalcoholic beverage worldwide for its unique flavor and healthful properties.As a characteristic non-protein amino acid in tea plants,theanine(y-glutamylethylamine)accounts for about 1-2%of the dry weight of fresh leaves of tea plants and it has a fresh taste and a variety of biological activities and health functions.Previous research indicated that a large amount of theanine is synthesized and accumulated in the young roots and buds of tea plants.However,as one of the major free amino acids,its physiological function is still unclear.Tea plants accumulate high concentrations of theanine,while tea plants are well adapted to high H+and Al3+concentrations.Whether there is any intriguing link between highly tolerance to Al3+and H+and highly accumulation of theanine in tea plant roots.In the present work,by physiological and biochemical tools,molecular biology,transcriptome and other technical methods,this study preliminarily discussed the influence of the change of theanine content in the roots of tea trees under aluminum acid stress,combined with aluminum acid resistance indicators and related gene expression,to elucidate the mechanism of acid-tolerant aluminium that theanine may participate in tea plants.The main conclusions of this experiment are as follows:1.By comparing and analyzing the difference of theanine and aluminium accumulation patterns in different organs of tea plant,we found that the content of theanine in adventitious roots was significantly higher than other tissues.And the content of aluminum in adventitious roots was significantly higher than that in other organs,followed by that in mature leaves.2.To compare the differences of theanine and ion content in the roots of hydroponic tea seedlings under aluminum acid stress,.The results showed that compared with the control group(0 mM Al),in the treatment of 0.4 and 2.5 mM Al,the tea roots absorbed and accumulated relatively high concentration of aluminum.In 0.4 mM Al treatment,theanine content was increased 1.70 times at 72 h compared with control,and in 2.5 mM Al treatment,it was significantly increased 1.30 times higher at 24 h and 48 h,respectively.Our study also found that the accumulation of procyanidins synthesized in the root tissues were significantly increased by 3.20 times under the stress of high aluminum treatment(2.5 mM Al).3.To elucidate the molecular mechanism,transcriptome sequencing analysis and qRT-PCR results showed that in 2.5 mM Al treatment,,the expression of the key gene CsGSII-1.1 was extremely significantly increased by 2.60 and 1.50 times at 24h and 48 h,respectively.The expression level of CsGSII-1.2 was significantly increased by about 1.50 times at 24 h and 48 h,and the expression level of CsGSII-1.3 was extremely significantly increased by 1.40 times at 48 h in the theanine metabolism.The expression levels of CsDFR was significantly increased by 2.60 and 2.00 times at 12 and 48 h,while the expression levels of CsANR and CsANS were increased by 1.50 and 1.90 times respectively at 12 h.The expressions of transporters related to aluminum stress,such as CsALMT1 and CsALMT2 were significantly increased by 3.30 and 3.90 times respectively at 48 h.CsALS1.9 expression was significantly increased by 1.30 and 2.10 times at 12 and 24 h,and CsALS3 expression was extremely significantly increased by 3.20 times at 12 h.The expression level of CsAIVT1 was significantly increased by 2.30 and 1.90 times at 24 and 48 h,respectively.4.Through transcriptome data analysis and sequence comparison,we cloned four CsSTOP transcription factors in tea plants and named them as CsSTOP1a,CsSTOP 1b,CsSTOP 2a and CsSTOP 2b.Tissue specificity analysis showed that CsSTOP1a and CsSTOP1b were expressed in different organs of tea plant,while CsSTOP2a and CsSTOP2b were specifically expressed in roots.In high-concentration aluminum treatment,CsSTOP1a,1b and 2b were significantly up-regulated by 4.2 and 1.7 and 2.6 times at 12 h after treatment,respectively.While CsSTOP2a was increased by about 1.6 times at 24 h after treatment.5.Wheat was treated by aluminum and theanine were added to the nutrient solution and the results showed that aluminum significantly inhibited the root elongation of wheat,while theanine had no effect on the normal growth of wheat.We continued to treated with different concentrations of aluminum and theanine in wheat,and citric acid as the positive control,we recorded the changes of root length 1 and 3 days after treatment.We found that when the concentration of Theanine and Al was 3:1,the inhibition of root elongation with aluminum could be effectively alleviated at 3 days. |
