Functional Analysis Of Chromatin Remodeling Complex SWR1 In Rice

Epigenetics is defined as the heritable changes in gene function with invariable DNA sequence during mitosis and/or meiosis period.The same genome can be transcribed into numerous epigenome through epigenetic modification.The various epigenome have important role in mammals and plants.In Arabidopsis(Arabidopsis thaliana L.)and rice(Oryza sativa L.),epigenetics is one of the hotspot for molecular biology.The term 'chromatin remodeling' is widely used to describe changes in chromatin structure that occur during regulatory processes.In the yeast and mammals,there are four different chromatin remodeling complexes,which are switching defective/sucrose non-fermenting(SWI/SNF)family,inositol requiring 80(INO80)family,chromodomain,helicase,DNA binding(CHD)family and imitationswitch(ISWI)family.These complexes all have specific protein structure with conserved function domains and involved in the control of gene expression,genome duplication,repair of DNA damage,and recombination of chromosomes.SWR1 complex is a subunit INO80 family,composed of SEF/AtSWC6,ARP6/AtSUF3 and PIE1 in Arabidopsis.The complex catalyzes the replacement of nucleosomal H2A with the H2A.Z variant on the FLOWERING LOCUSC(FLC)promoter,increase the expression of FLC.By the control of FLC,SWR1 complex is involved in regulation of flowering time in Arabidopsis.However,the functions of SWR1 complex in rice have not been known.To explore the function of SWR1 complex in rice,the method of reverse genetics was used in this study.The homologs of SEF,ARP6 and PIE1 genes in rice are obtained through BLAST.They are single copy genes in rice,termed OsSEF,OsARP6 and OsPIE1.The results of sequence alignment and phylogenetic analysis show that the three genes are evolutionary conserved.To conduct functional studies,over-expression and RNAi mutant were created by DNA recombination and transgenic technology.At the same time,we generate the gene specific promoter driven CDS fused to GFP transgenic lines and gene specific promoter driven the GUS reporter transgenic lines.Nuclear localization of the OsSEF,OsARP6 and OsPIE1 proteins are observed through the stable transgenic plants of Arabidopsis harboring the gene specific promoter driven CDS fused to GFP construct.The expression patterns of the three genes are also investigated by using GUS staining assay and quantitative RT-PCR.The three genes are expressed in all the tissues and organs tested,including newly emerging leaf,expending leaf,fully expended leaf,around the shoot apex,root,panicle,stem and sheath.The phenotype and molecular mechanisms are explored in their over-expression and RNAi mutants.The primary results revealed that SWR1 complex may participates in the control of heading date in rice.The more work need to be done to dissect the functions of OsSEF,OsARP6 and OsPIE1 in SWR1 complex of rice.