The Regulation Of Ethylene On Arsenic Tolerance In Wheat(Triticum Aestivum L.) And Its Mechanisms

Arsenic(As)is a highly toxic metalloid and it will inhibit plant growth and reduce the production of crops after entering plant cells.Therefore,understanding the tolerant mechanism of crops to As is particularly important for crop production.As an important hormone,ethylene mediates plant growth and development.Previous studies showed ethylene is induced by various stresses and participated in regulating the stress resistance of plants.However,it is unclear whether ethylene is involved in the regulation of crops tolerance to heavy metal stress.In the present study,wheat(Nannong 0686,NN0686)was used 1)to analyze the expression of genes related to ethylene biosynthesis and signal transduction in wheat seedlings under As stress using RNA-seq;2)to investigate the effects of ethylene on wheat As stress by supplying exogenous ethephon,ACC and CoCl2(an inhibitor of ACC oxidase);and 3)to over-express two wheat genes related to ethylene synthesis and signal transduction in Arabidopsis and to study the tolerance of transgenic Arabidopsis lines to As stress.The objective of the present study is to illustrate the alleviation of ethylene on crop As stress,and thus to provide an evidence and a basis for further study on the mechanisms of plants response to As.The main results of the present study are as follows:1)According to the results of RNA-seq,the positive regulatory factors of ethylene synthesis and signal pathways were up-regulated in root of wheat under As stress,especially for ACC oxidases and Nramp family genes in signal pathways.It is presumed that various genes and enzymes which are positively regulated ethylene synthesis in root of wheat were enhanced under As stress,thus ethylene was quickly synthesized to alleviate As toxic to wheat.2)Exogenous ethephon or ACC significantly increased root elongation,chlorophyll content and root activity,while reduced MDA content and As concentration of wheat under As stress,especially for exogenous ethephon.The reverse results have been observed after addition of CoCl2,a inhibitor of ethylene synthesis The results showed that ethylene enhanced wheat As tolerance,while serious As toxicity to wheat was found when ethylene synthesis was inhibited.3)Overexpression of 325700(a ACC oxidase gene)and 036000(a Nramp family gene)in Arabidopsis thaliana resulted in the enhancement of its As tolerant ability.Compared with Col-vec,the root elongation and chlorophyll content of overexpressed lines increased,while the MDA content and As concentrations decreased significantly under As stress,especially for the lines overexpressed ACC oxidase gene of wheat..The increase in the expression of homologous genes of 325700 and 036000 in Arabidopsis Col-0 was also observed under As exposure.The results showed that As induced the expression of genes related to ethylene synthesis and signalingin Arabidopsis.Overexpression of wheat 325700 and 036000 genes improved Arabidopsis tolerance to As.The above results showed wheat seedlings increased As resistance by enhancing ethylene synthesis or signal transduction under As stress.