Preliminary Studuies On The Function Of Arabidopisis IQM4 Gene

Five calmodulin-binding protein?CaMBP?families have been found to possess the IQ motif?s?in plants,including myosin,CNGC,IQD,CAMTA and IQM family.Arabidopsis IQM4?AT2G26190?,a member of IQM family,was highly homologous to the reported IQM1,and the gene functions remain unknown.Therefore,characterization of IQM4 function will contribute to the comprehensive understanding of the IQM family during plant growth and development peroid.In this paper,transgenic P_IQM4:GUS lines were constructed and the expression profile of IQM4 was analyzed;molecular identification of candidate iqm4 mutants were performed through PCR and RT-PCR technique.The detailed phenotype characterization of two loss-of-function mutants and three overexpressions of IQM4 lines was performed.The iqm1iqm4 double mutant was constructed by genetic crossing and performed the phenotype characterization.The main results are as follows:1.Histochemical GUS staining showed that IQM4 was expressed strongly in embryo of mature seed,root and cotyledons of seedlings,rosette leaf and silique of mature plants.Exogenous ABA inhibited IQM4 expression levelof seedlings.2.Comparison to wild type,loss-of-function mutants iqm4-1 and iqm4-2 were significantly resistant to exogenous ABA on seed germination,but were undifferentiated to salt and osmosis stress;the stomatal aperture of iqm4 mutant was significantly smaller than that of Col during light-induced stomatal opening;however,there was no significant difference during darkness-induced stomatal closure.With the treatment of exogenous ABA,iqm4-1 seedlings exhibited higher expression level of ABI5 and lower of FUS3 and WRKY40.3.Comparison to wild type,overexpression lines of IQM4 showed significantly sensitive to exogenous ABA and Mannitol in seed germination;but were significantly resistant to salt stress.4.With treatment of exogenous ABA,the phenotype of iqm1iqm4 double mutant was the same to that of iqm4-1 and iqm4-2 mutant in seed germination rate,fresh weight per seedling,primary and lateral root growth of seedlings;the stomatal open and closure of iqm1iqm4 was also similar to that of iqm4-1 and iqm4-2;and there was different influence of IQM1 and IQM4 deletion on the gene expression levels of ABA signaling and stomatal regulation-related marker genes.These results suggested that Arabidopsis IQM4 plays an important role in the physiological process of ABA-inhibited seed germination.IQM4 was involved in light-induced stomatal opening.As the function of IQM4 was similar to IQM1,it was deduced that IQM4 and IQM1 play a role in the same signaling pathway.