Screening In Arabidopsis RopGEFs Genes As Upstream Activators In The ROP10-dependent ABA Signaling Pathway

Rho-related GTPases of plants (ROPs) function as molecular switches inplant growth and development. They participate in controlling many signaltransduction pathways. Research shows that ROPs are involved in the ABAsignaling by suppressing the ABA-induced responses including stomatal closure,root elongation and seed germination. Plant RopGEFs (guanine nucleotideexchange factors) are identified as ROP activator proteins in Arabidopsis. Theactivation of GTPase needs the catalysis of GEFs with the conversion frominactive GDP-GTPase into active GTP-GTPase. ROP10, a member of ROPs, isinvolved in ABA signaling as a specific negative regulator of Abscisic Acidresponses in Abrabidopsis. However, the functions of RopGEFs in development orstress response of plant are still unclear.The corresponding RopGEF gene expression in ropgefs was analyzed byReal-time fluorescence quantitative PCR to verify that these mutants are reallyT-DNA insert homozygous. The expression profiles of ROP10and MYB2genes inwild type (Col-0) and ropgefs seedlings in response to different concentration ofABA were detected. The results showed that mRNA expression levels of ROP10were lower than Col-0in ropgef12and13but consistent with Col-0in ropgef14.The mRNA expression levels of ROP10were influenced little in ropgef12and13but largely in ropgef4、11and14. Meanwhile, comparing to the T-DNA insertionmutant of ROP10(rop10-1), under1and50μM ABA treatment, the MYB2geneexpression profile in ropgef12and13was similar to rop10-1, while was differentwith rop10-1in ropgef4、11and14.The phenotypes such as seed germination, seedling root growth and waterloss of these mutants and Col-0were observed responsing to exogenous ABA. Thephenotypes in ropgef4、11、12、13and14have no significant differences withCol-0, while ropgef14has the same sensitivity compared with Col-0. Comparedwith the gene expression profile and phenotype analysis, it can be predicted thatRopGEF12and13may participate in ABA signal transduction, but RopGEF14may be not involved in this pathway dependently. What’s more, the functions ofRopGEFs genes might be redundant. The results provide certain basis for furtherresearch on the role of RopGEFs family and mechanism of regulation in ABAsignal transduction.