Functional Analysis Of GhROP6 In Cotton Responsive To Verticillium Dahliae

Verticillium wilt is a fungus disease affecting cotton production,hence identifying cotton resistance gene and exploring cotton resistance mechanism provide crutial basis for disease resistance breeding.ROP is a plant specific subfamily of RHO-GTPase,which plays a vital role in plant innate system and development.Based on the results of microarray data analysis,a gene sharing high similarity to At ROP6 in amino acid was isolated and named Gh ROP6.Through RACE amplification,we obtained the full-length sequence of the gene.Using virus-induced gene silencing,we preliminary analized the function of the gene and proved that it played important roles in interaction between cotton and Verticillium dahliae.The main results are as follows:1.The expression pattern analysis showed that GhROP6 expressed in every tested tissue of upland cotton with higher expression level in root,stem,petal and anther.The results of hormone treatment and inoculation with Verticillium dahliae show that Gh ROP6 is likely to be involved in response to JA pathway and the transcript level decreases when inoculated with V.dahliae.2.To explore the function of the gene,virus induced gene silencing was employed and the corresponding vector of Gh ROP6 was completed and transferred into Agrobacterium.To inhibit the expression of Gh ROP6 in cotton,we use agrobacterium-mediated cotton cotyledons injection.After two weeks of infiltration,cotton plants inoculated with V.dahliae strain V991 were used to analyze the influence of its resistance.The results showed that the Gh ROP6-silenced plants were more susceptible to V.dahliae compared to the TRV:00.And the gene expression analysis indicated that knock-down of Gh ROP6 might inhibit JA synthesis.3.In addtion,we also found that the content of lignin in GhROP6-silenced plants was much less compared to TRV:00 control plants and the expression level of genes involved in lignin systhesis was also decreased in Gh ROP6-silenced plants.Moreover,increased level of H2O2 was detected in Gh ROP6-silenced plants compared to control plants after the V.dahliae fungus invasion plants.4.The overexpression and RNA interference vectors of GhROP6 were completed respectively and transformed in upland cotton cv YZ1.The phenotypes of transgenic plants were characterized.Little roots,small plant architecture as well as unnormal flowering were found in Gh ROP6 silenced transgenetic cotton plants,which suggested that Gh ROP6 may play a vital role in cotton development,while overexpression of Gh ROP6 has little effect on cotton plants.All the above results indicated that GhROP6 might involve in defense response of cotton to V.dahliae by regulating multiple signaling pathways.However,the resistance mechanism mediated by Gh ROP6 need further study.