Down-regulation of RFL, the FLO/LFY homolog of rice, accompanied with panicle branch initiation.
FLORICAULA (FLO) of Antirrhinum and LEAFY (FLY) of Arabidopsis regulate the formation of floral meristems. To examine whether same mechanisms control floral development in distantly related species such as grasses, we isolated RFL, FLO-LFY homolog of rice, and examined its expression and function. Northern analysis showed that RFL is expressed predominantly in very young panicle but not in mature florets, mature leaves, or roots. In situ hybridization revealed that RFL RNA was expressed in epidermal cells in young leaves at vegetative growth stage. After the transition to reproductive stage, RFL RNA was detected in all layers of very young panicle including the apical meristem, but absent in the incipient primary branches. As development of branches proceeds, RFL RNA accumulation localized in the developing branches except for the apical meristems of the branches and secondary branch primordia. Expression pattern of RFL raised a possibility that, unlike FLO and LFY, RFL might be involved in panicle branching. Transgenic Arabidopsis plants constitutively expressing RFL from the cauliflower mosaic virus 35S promoter were produced to test whether 35S-RFL would cause similar phenotype as observed in 35S-LFY plants. In 35S-RFL plants, transformation of inflorescence meristem to floral meristem was rarely observed. Instead, development of cotyledons, rosette leaves, petals, and stamens was severely affected, demonstrating that RFL function is distinct from that of LFY. Our results suggest that mechanisms controlling floral development in rice might be diverged from that of Arabidopsis and Antirrhinum.
Kyozuka
J
J
Laboratory of Plant Molecular Genetics, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, 630-01 Japan. junko@bs.aist-nara.ac.jp
Konishi
S
S
Nemoto
K
K
Izawa
T
T
Shimamoto
K
K
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000378:metabolism; D029681:Arabidopsis Proteins; D001483:Base Sequence; D017931:DNA Primers; D018506:Gene Expression Regulation, Plant; D015723:Gene Library; D018519:Meristem; D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000096:biosynthesis* / Q000737:chemistry*; D030821:Plants, Genetically Modified; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors
D029681:Arabidopsis Proteins; D017931:DNA Primers; C111245:FL protein, Oryza sativa; C083654:FLO protein, Antirrhinum majus; C074747:LFY protein, Arabidopsis; D010940:Plant Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors