The gene FLORAL ORGAN NUMBER1 regulates floral meristem size in rice and encodes a leucine-rich repeat receptor kinase orthologous to Arabidopsis CLAVATA1.
The regulation of floral organ number is closely associated with floral meristem size. Mutations in the gene FLORAL ORGAN NUMBER1 (FON1) cause enlargement of the floral meristem in Oryza sativa (rice), resulting in an increase in the number of all floral organs. Ectopic floral organs develop in the whorl of each organ and/or in the additional whorls that form. Inner floral organs are more severely affected than outer floral organs. Many carpel primordia develop indeterminately, and undifferentiated meristematic tissues remain in the center in almost-mature flowers. Consistent with this result, OSH1, a molecular marker of meristematic indeterminate cells in rice, continues to be expressed in this region. Although floral meristems are strongly affected by the fon1-2 mutation, vegetative and inflorescence meristems are largely normal, even in this strong allele. We isolated the FON1 gene by positional cloning and found that it encodes a leucine-rich repeat receptor-like kinase most similar to CLAVATA1 (CLV1) in Arabidopsis thaliana. This suggests that a pathway similar to the CLV signaling system that regulates meristem maintenance in Arabidopsis is conserved in the grass family. Unlike CLV1, which is predominantly expressed in the L3 layer of the shoot meristem, FON1 is expressed throughout the whole floral meristem, suggesting that small modifications to the CLV signaling pathway may be required to maintain the floral meristem in rice. In addition, FON1 transcripts are detected in all meristems responsible for development of the aerial part of rice, suggesting that genes sharing functional redundancy with FON1 act in the vegetative and inflorescence meristems to mask the effects of the fon1 mutation.
Suzaki
Takuya
T
Graduate School of Agricultural and Life Sciences, University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
Sato
Makoto
M
Ashikari
Motoyuki
M
Miyoshi
Masahiro
M
Nagato
Yasuo
Y
Hirano
Hiro-Yuki
HY
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry*; D003001:Cloning, Molecular; D035264:Flowers / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism / Q000648:ultrastructure; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D017403:In Situ Hybridization; D007930:Leucine / Q000032:analysis; D018519:Meristem / Q000254:growth & development* / Q000378:metabolism; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D012275:Oryza / Q000166:cytology / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D010641:Phenotype; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D020794:Receptor Protein-Tyrosine Kinases / Q000737:chemistry*; D020449:Repetitive Sequences, Amino Acid; D016415:Sequence Alignment
D029681:Arabidopsis Proteins; D010940:Plant Proteins; D020794:Receptor Protein-Tyrosine Kinases; C118166:CLV1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases; D007930:Leucine