Functions Of Small G Protein RAB5 In Salt Tolerancein And Phenotypic Characterization And Gene Mapping Of A Thermo-sensitive Albino Mutant Tsa1 In Rice

This article contains two research projects,namely functions of small G protein RAB5 in salt tolerancein and phenotypic characterization and gene mapping of a thermo-sensitive albino mutant tsal in Rice.It has been reported that ARA6 one of RAB5 family gene in Arabidopsis play a regulatory function when response to salt stress.Also found ARA6 highly homologous genes RAB5b/d in Rice.By salt treating the transgenic Arabidopsis which overexpress RAB5b/dCA(constitutive active),we found that overexpressd RAB5b/dCA can enhance plant tolerance to salt stress,for further studying the function of RAB5 homologous genes in salt tolerance in Rice.Though transient expression in tobacco,we found that RAB5b/dCA co-localization with AtPIP2A which is plasma membrane marker.Indicate RAB5b/d mediate the vesicle transport from endosome to the plasma membrane pathway,which is difference from the traditional RAB5 small G protein RAB5a mediated pathway.But RAB5b/dWT(wild type)co-localization with AtVSR2,the marker of late endosome PVC,indicating the function of RAB5b/d,not only mediating the vesicle transport pathway from endosome to the plasma membrane,but also having additional functions.Further studies showed that RAB5b/d co-localization with the OsHKT1,a plasma membrane Na+/H+antiporter,we presumed RAB5b/d through regulating the transport proteins,like HKT1,which response to salt stress,involved in salt tolerance in Rice.Although people has made positive studies on salt tolerance in Rice,but the salt tolerance mechanism of Rice is far from been parsed,such as the relationship between vesicle transport with the salt tolerance in Rice is almost a research gap.This study has an important significance in providing better information for genetic improvement of Rice.We also found a thermo-sensitive albino mutant tsal which was obtained fromNingjing36 induced by Ethyl methane sulfonate(EMS).The mutant develops albinotic under low temperature(20-24℃),and the color of mutant leaves is comparable with wild-type under high temperature(32 ℃).Compared with wild type,the chlorophyll a and carotene content of mutant albinotic leaves obviously decrease under low temperature condition.Microscope observation showed that the quantity of normal chlorophyll is significant decreased in mutant.Besides,mutant cell developed a large number of small abnormal chloroplasts.Transmission electron microscopy observation found that the abnormal chloroplast in albinotictissue of mutant has no obvious thylakoid stack.These results indicated that tsal mutant has defect in the chloroplast development under low temperature.Genetic analysis indicated that the mutant phenotype was controlled by a single recessive nuclear gene.Genetic mapping of the mutant gene was conducted using 368 recessive individuals from F2 population of tsa1/NJ11,the target gene was finally located in a 163kb region on the chromosome 5.This study provide a basis work for map-based cloning and functional analysis of the target gene.