Myrosinase TGG1 Is Involved In Drought Resistance In Arabidosis Thaliana

Glucosinolate, an important secondary matebolite which is rich in nitrogen and sulfur elements, extensively exists in cruciferae plants with multiple biological effects like resisting pest and disease damage, creating peculiar flavor and preventing & curing cancers as well as comprehensive research values and economic values. However, as glucosinolate itself is a kind of inert substance, most of its biological functions need to be completed by relying on its own hydrolyzate. Myrosinase is hydrolytic enzyme of glucosinolate, and in general condition, the two separately exist in different positions of plant cells. When the plant suffers mechanical damage, spatial isolation between myrosinase and glucosinolate will be broken, and the two will meet, which generates reaction, and then nontoxic glucosinolate will be hydrolyzed into various toxic hydrolyzates which will exert different biological effects. TGG1, the most important kind of myrosinase with the broadest existence scope and the largest expression quantity among myrosinase family, mainly exists on overground part, and besides, it together with TGG2 in the same family has functional redundancy.TGG1 is the most important known variety in the family of myrosinase gene. As shown by a growing number of researches, TGG1 can be involved in many other aspects of physiological process besides controlling the glucosinolate catabolism and thus enabling the plant to make preventive reaction to the biotic stress such as the pest. According to some researches, the absence of TGG1 gene will hinder the ABA-induced closure of the stomata. Hence, it can be inferred that TGG1 is likely to be related to the water metabolism of the plant and also participate in the drought-resistance reaction. This research will make an experiment to verify the assumption.By constructing TGG1 over-expression vector driven by 35 S promoter, this study shifted TGG1 into Arabidopsis thaliana with inflorescence dip dyeing method mediated by agrobacterium and obtained transgenic plant homozygote with stable expression. Taking wild-type transgenic plant with over expression of TGG1 as experimental material, this paper conducted drought stress experiment, and experimental results showed that:(1) Under drought stress simulated by 150 mmol/L mannitol, 35: TGG1 seeds could basically sprout with relatively vigorous growth momentum; while WT seeds could hardly sprout, and few sprouting plants were quite fragile with growth speed obviously slower than that of 35S:TGG1.(2) Under arid environment simulated by mannitols of two concentration gradients—150 mmol /L and 250 mmol /L,both average relative electric conductivities of 35S:TGG1 were significantly lower than those of wild type, which proved that their damage degree was lower than that of wild type.(3) Relative dehydration rate of detached leaf of 35S:TGG1 was significantly slower than that of wild type, and withering degree of WT detached leaf after 5 h was obviously greater than that of 35S:TGG1.(4) Under natural drought stress, relative dehydration rate of 35S:TGG1 was significantly slower than that of wild type, while average survival rate after rehydration was significantly higher than that of wild type.(5) Stoma observation results indicated that stoma of transgenic plant with over expression of TGG1 had higher sensitivity to ABA treatment, and stoma closing degree was significantly higher than that of wild type plant.Above research results indicated that over expression of TGG1 gene could significantly improve drought resistance of Arabidopsis thaliana, and its resistance mechanism might be related to closing degree of stoma under stress.Previous research emphasis of glucosinolate degradation was mainly put on biological stresses like pest and disease damage, while effect of glucosinolate degradation in abiotic stress had drawn little concern. This research testified that glucosinolate degradation was closely related to drought resistance of plants, over expression of TGG1 could accelerate stoma closing by enhancing its sensitivity to ABA, and then significantly intensify drought resistance of plants,which will provide the theoretical basis and data reference for the role of glucosinolate and its metabolite in the abiotic stress as well as the relevant molecular mechanism.