The Regulatory Mechanism Of ACOS5, An Important Gene For Sporopollenin Synthesis, In Tapetum Cells

Pollen wall is the outermost layer of the pollen grain.Its hard and viscid structure plays an important role in the process of protection,communication and recognition,which guarantee the seed plants able to survive and develop in the complex land environment.The defective pollen wall leads to male sterility which provides crucial breeding tools to harness hybrid vigor.The sporopollenin is thought to be the major composition of sexine,which component is complex.Currently,multiple genes involved in sporopollenin synthesis have been reported.The function of a key member in sporopollenin synthesis pathway,ACOS5,has been reported.However,the regulatory mechanism of these enzymes has not been clarified.In this paper,(1)we analyzed the expression level of ACOS5 in tdf1,ams,ms188 and ms1 mutant anther and found the expression level of ACOS5 severely reduced in tdf1 and ams,a slight decrease in ms188 and have some increase in ms1.(2)Chromatin immunoprecipitation(Ch IP)and Electrophoretic Mobility Shift Assays(EMSA)assays showed that all of TDF1,AMS,MS188 are can combined with ACOS5 promoter region.(3)Transient expression system in tobacco proved that MS188 can directly activate ACOS5 expression.(4)When MS188 driven by the AMS promoter is expressed in ams mutant,the expression level of ACOS5 recovered normally.Taken together,these results indicated that both AMS and MS188 paticipated in the sporopollenin synthesis pathway.The AMS function in binding the promoter of targets,and recruiting MS188 to activite the targets' expression.