title: The polycomb group gene EMF2B is essential for maintenance of floral meristem determinacy in rice.
abstract: Polycomb Repressive Complex 2 (PRC2) represses the transcriptional activity of target genes through trimethylation of lysine 27 of histone H3. The functions of plant PRC2 have been chiefly described in Arabidopsis, but specific functions in other plant species, especially cereals, are still largely unknown. Here we characterize mutants in the rice EMF2B gene, an ortholog of the Arabidopsis EMBRYONIC FLOWER2 (EMF2) gene. Loss of EMF2B in rice results in complete sterility, and mutant flowers have severe floral organ defects and indeterminacy that resemble loss-of-function mutants in E-function floral organ specification genes. Transcriptome analysis identified the E-function genes OsMADS1, OsMADS6 and OsMADS34 as differentially expressed in the emf2b mutant compared with wild type. OsMADS1 and OsMADS6, known to be required for meristem determinacy in rice, have reduced expression in the emf2b mutant, whereas OsMADS34 which interacts genetically with OsMADS1 was ectopically expressed. Chromatin immunoprecipitation for H3K27me3 followed by quantitative (q)RT-PCR showed that all three genes are presumptive targets of PRC2 in the meristem. Therefore, in rice, and possibly other cereals, PRC2 appears to play a major role in floral meristem determinacy through modulation of the expression of E-function genes.
authors.affiliation: Plant Biology Department, University of California Davis, 1 Shields Ave, Davis, CA 95616, USA.
authors.forename: Liza J
authors.initials: LJ
authors.lastname: Conrad
authors.forename: Imtiyaz
authors.initials: I
authors.lastname: Khanday
authors.forename: Cameron
authors.initials: C
authors.lastname: Johnson
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Guiderdoni
authors.forename: Gynheung
authors.initials: G
authors.lastname: An
authors.forename: Usha
authors.initials: U
authors.lastname: Vijayraghavan
authors.forename: Venkatesan
authors.initials: V
authors.lastname: Sundaresan
mesh_terms: D047369:Chromatin Immunoprecipitation; D035264:Flowers / Q000235:genetics*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D006657:Histones / Q000378:metabolism; D026161:MADS Domain Proteins / Q000235:genetics / Q000378:metabolism; D018519:Meristem / Q000235:genetics / Q000502:physiology*; D008745:Methylation; D009154:Mutation; D012275:Oryza / Q000235:genetics* / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D063146:Polycomb-Group Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D006657:Histones; D026161:MADS Domain Proteins; D010940:Plant Proteins; D063146:Polycomb-Group Proteins
keywords: EMF2B; MADS box; Oryza sativa; floral meristem; polycomb