title: SUPERWOMAN1 and DROOPING LEAF genes control floral organ identity in rice.
abstract: We analyzed recessive mutants of two homeotic genes in rice, SUPERWOMAN1 (SPW1) and DROOPING LEAF (DL). The homeotic mutation spw1 transforms stamens and lodicules into carpels and palea-like organs, respectively. Two spw1 alleles, spw1-1 and spw1-2, show the same floral phenotype and did not affect vegetative development. We show that SPW1 is a rice APETALA3 homolog, OsMADS16. In contrast, two strong alleles of the dl locus, drooping leaf-superman1 (dl-sup1) and drooping leaf-superman2 (dl-sup2), cause the complete transformation of the gynoecium into stamens. In these strong mutants, many ectopic stamens are formed in the region where the gynoecium is produced in the wild-type flower and they are arranged in a non-whorled, alternate pattern. The intermediate allele dl-1 (T65), results in an increase in the number of stamens and stigmas, and carpels occasionally show staminoid characteristics. In the weakest mutant, dl-2, most of the flowers are normal. All four dl alleles cause midrib-less drooping leaves. The flower of the double mutant, spw1 dl-sup, produces incompletely differentiated organs indefinitely after palea-like organs are produced in the position where lodicules are formed in the wild-type flower. These incompletely differentiated organs are neither stamens nor carpels, but have partial floral identity. Based on genetic and molecular results, we postulate a model of stamen and carpel specification in rice, with DL as a novel gene controlling carpel identity and acting mutually and antagonistically to the class B gene, SPW1.
authors.affiliation: Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Nagasawa
authors.forename: Masahiro
authors.initials: M
authors.lastname: Miyoshi
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Sano
authors.forename: Hikaru
authors.initials: H
authors.lastname: Satoh
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Hirano
authors.forename: Hajime
authors.initials: H
authors.lastname: Sakai
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Nagato
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D035263:Flowering Tops / Q000502:physiology*; D035264:Flowers / Q000235:genetics / Q000254:growth & development; D018506:Gene Expression Regulation, Plant; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D012275:Oryza / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D018398:Homeodomain Proteins; D010940:Plant Proteins