OsRacD, belonging to rice (Oryza sativa L. ssp. japonica) Rho family of the small GTPases, is a pivotal gene involved inrice photoperiod fertility conversion of photoperiod sensitive genic male sterile rice which influences the rice fertility viacontrolling the pollen tube growth. Using OsRacD as bait, two GDP dissociation inhibitor genes designated as OsRhoGDI1and OsRhoGDI2 were screened by yeast two-hybrid system. To further study the regulation mechanism of OsRhoGDIs,and also the relationships between OsRhoGDIs and OsRacD, the upstream regulation sequences of OsRhoGDI1 andOsRhoGDI2 were cloned by PCR, and the cis-elements in the promoters were predicted using internet tools in this study.The results showed that there were several kinds of response elements, such as phytohormone response elements, light-regulated elements and adversity induced elements in the promoters of OsRhoGDIs, some of which were similar.Comparing with the promoter of OsRacD, several pollen tube germination related elements were found. On one hand, theexpression and regulation mechanism of OsRhoGDIs were complex, they may be regulated by several signaling pathwayscommonly, and the regulation mechanisms were similar to some extent. On the other hand, it was suggested that thefertility of photoperiod sensitive genic male sterile rice may be controlled by the cooperative expression of OsRhoGDIsand OsRacD.
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