ROPGEF5 Plays A Role In Root Vascular Tissue Development In Arabidopsis Thaliana

In Arabidopsis thaliana,ROPGEFs(Guanine Nucleotide Exchange Factor),as the upstream activation factor of the small G protein RAC/ROP,catalyzes the exchange of ROPs from the GDP-binding inactive form(GDP-ROPs)to the(GTP-binding active form(GTP-ROPs),and then participates in the regulation of plant growth,development and stress response.Arabidopsis contains 14 ROPGEFs genes(ROPGEF1-14)that encode ROPGEF proteins,which are characterized by a conserved PRONE domain.At present,serial studies have reported that ROPGEFs play important regulatory roles in plant growth and development.In this study,we reported that ROPGEF5 affected the development of root vascular tissue in Arabidopsis thaliana.The major results are presented as following:(1)Microarray profiling data showed that ROPGEF5 was widely expressed in embryo seedling root inflorescence meristem and silique etc.The expression pattern of ROPGEF5 was further verified by GUS histochemical staining of ROPGEF5 pro-GUS.ROPGEF5 homologs ROPGEF1 and ROPGEF6 they were also found to have similar expression patterns in root vascular tissues by GUS histochemical staining.(2)Through the analysis of the mutant phenotype by DICl microscope and laser confocal microscope,we found that ropgef5-1,ropgef5-2,ropgef5-3 all have root vascular development defects,indicating that ROPGEF5 plays a role in root vascular development.(3)The fluorescence signal intensity of PIN1pro-PIN1-GFP and DR5-GFP was obviously decreased,while the expression of ARR5pro-RFP was expanded.This results suggest that ROPGEF5 may play a role in root vascular development by regulating hormone signals.(4)By cytokinin treatment of the mutants ropgef5-2,ropgef5-3,ahp6-1 and wild type(WT),we found that the mutants were more sensitive to cytokinins than WT,and the ropgef5 mutants showed a similar phenotype to that of ahp6 mutant.In root,cytokinin and auxin are antagonistic to each other,indicating that ROPGEF5 may negatively regulatecytokinin signaling on its function of affecting vascular development.(5)Yeast two-hybrid experiment showed a direct interaction between ROPGEF5 and AHP6,and the the conserved PRONE domain directly interacts with AHP6.These results showed that ROPGEF5 plays an important role in root vascular tissue development.