OsEM2B Mediated Floral Organ Development Research In Rice

Rice is one of the most important food crops in the world, the development of flower organs directly affect the yield and quality of rice. In Arabidopsis thaliana, the study of flowers organs development is relatively perfect, putting forward the classical ABC model, the model think the development of flowers organs is regulated by ABC family of genes through interactions. In addition to the ABC model, whether there is other regulation of floral organ development style? With further research, a new way--epigenetic regulation, is found in Arabidopsis thaliana, participate in the development of flower organs.EMBRYONIC FLOWER (EMF), has a role of H3lysine methylation (H3K27me3) in histone modification in Arabidopsis thaliana. There are two EMF gene in Arabidopsis thaliana, EMF1and EMF2. Studies have shown that the EMF gene mainly involved in the development of floral meristem and control the expression of flower organ specific gene. The molecular mechanism indicates that EMF2act on the gene chromatin interact with EMF1protein by H3K27me3. Overall, there is another kind of flower organ regulation in Arabidopsis thaliana:by EMF2mediated H3K27me3epigenetic regulation.Rice, as a mode of monocot plants, formed a specific "ABC" model through a variety of floral organ mutants, but for whether there is any other way of regulation of floral organ development is rarely reported. OsEMF2b, a homologous gene of EMF2in rice, is whether can regulate the floral organ development though the way H3K27me3? We take OsEMF2b T-DNA insertion mutants as the research object, using the phenotypic observation, gene chip and Q-PCR experimental methods, to research OsEMF2b regulate the floral organ development. The preliminary results are summarized as bellow:1. Phenotypic observation:the osemf2b display serious flower organ defects, the defects are almost found in four wheel flower organ, mainly in the number of flower organs. Through the statistics ratio of flowers organs, we found that50.9%of flower appears a similar glum structure inside the lemma/palea, with about30.4%lemma absence. In the inner wheel flower organs, about82.6%of the flower appear lodicule missing, the degree of loss is1-2pieces, and about70.8%of stamens reduced, to reduce the number of2-4, carpel showed a cluster structure, accounting for21.7%. This suggests OsEMF2b involved in regulation of rice spikelet development.2. Gene chip expression results. To explore OsEMF2b expression background, we take gene chip analysis in seedling stage and in pillow from the zero periods. we use the expression level changes2times as the standard, we found that there are about111gene expression changes in seeding stage, and about8500gene in heading stage. This suggested OsEMF2b regulation has certain specific space and time. According to the osem/2b phenotype, there are three flower organs identity gene:OsMADS2, OsMADS6, OsMADS16, which expression decreased significantly in the mutant, respectively is44,53, and18times.3. Real-time quantitative PCR results. For the osemf2b flower organs mutation phenotype, we use real-time quantitative PCR technology to analyze the expression change trend of the flower organ identity gene:OsMADS2, OsMADS6, OsMADS16with the chip results. The results showed that the consistency between Quantitative PCR results and chip result was100%. At the same time we analyzed OsMADS2, OsMADS6, OsMADS16three genes expression in young panicle, results showed that the three genes expression decreased obviously, and the expression change trend is consistent with the chip results(seeding chip and heading stage chip), but decreased expression level increased.4. Regulation of flower development analysis.4.1OsEMF2b regulate OsMADS2expressionOsMADS2belongs to B clade gene in rice, control the lodicule and stamen development. In function of OsMADS2deletion mutants, found that the genes controlling cell along adaxial and abaxial division and differentiation, is cause parenchyma and must be special catheter lodicule development (YADAV et al.,2007). In osemf2b, OsMADS2expression was severely decreased the expression change to44times, consistent with our missing lodicule phenotype, showing that OsEMF2b regulate the expression of OsMADS2to control lodicule development.4.2OsEMF2b regulate OsMADS6expressionOsMADS6is AGAMOUS-Like (AGL6) gene, necessary to spikelet each round of floral organ development. Li found that in osmads6all flower organ except palea was changed, consistent with osemf2b phenotype which almost each wheel flower organ is changed, and at the same time the OsMADS6expression was strongly decreased in osemf2b, to53times. It shows that OsEMF2b regulate the expression of OsMADS6affecting the growth of spikelet.4.3OsEMF2b regulate OsMADS6expressionOsMADS16belongs to B clade gene in rice. Xiao use RNAi technology to study the function of OsMADS16, finding that lodicule and stamens was changed, the lodicules transforming into a similar lemma structure, and stamens into carpel. It shows that OsMADS16controls the lodicule and stamen development. In osemf2b OsMADS16decreased expression of up to17times, consistent with the missing lodicule and stamens phenotype. It suggests that OsEMF2b regulate the expression of OsMADS16to control lodicule and stamen development.4.4OsEMF2b has tissue and stage specificity for regulating the OsMADS2,OsMADS6, and OsMADS16The chip datas show that OsMADS2,OsMADS6, OsMADS16appear significant expression change in heading stage, but not in seeding stage, showing that OsEMF2b regulate OsMADS2,OsMADS6, OsMADS16for tissue specificity. At the same time, these genes have greater expression change in young panicle than in pillow from the zero periods, diplaying that the regulation of OsMADS2,OsMADS6, and OsMADS16has stage specificity.Overall, we think that in rice, there is another regulatory mechanism of flower development---OsEMF2b participation way of H3K27me3. Due to currently unable to make sure the role of OsEMF2b protein, aiming at phenotypic differences of flower development, according to the chips and quantitative PCR results, we can make sure the flower organ identity genes OsMADS2, OsMADS6, OsMADS16involved in this regulation. Proposed on this basis, the further research will take as follows:make the three genes over-express in osemf2b, observing the lemma, lodicule and stamens phenotype are whether recovered, at the same time taking CHIP technology to test H3K27me3level of these genes, make sure the regulation way of OsEMF2b.