Rice GTPase OsRacB:Potential Accessory Factor in Plant Salt-stress Signaling

As the sole ubiquitous signal small guanosine triphosphate-binding protein in plants,Rop geneplays an important role in plant growth and development.In this study,we focus on the relationship betweenthe novel rice Rop gene OsRacB and plant salt tolerance.Results show that OsRacB transcription is highlyaccumulated in roots after treatment with salinity,but only slightly accumulated in stems and leaves under thesame treatment.Promoter analysis showed that OsRacB promoter is induced by salinity and exogenoussalicylic acid,not abscisic acid.To elucidate its physiological function,we generated OsRacB sense andantisense transgenic tobacco and rice.Under proper salinity treatment,sense transgenic plants grew muchbetter than the control.This suggests that overexpression of OsRacB in tobacco and rice can improve plantsalt tolerance.But under the same treatment,no difference could be observed between OsRacB antisenseplants and the control.The results indicated that OsRacB is only an accessory factor in plant salt tolerance.