Expression level of ABERRANT PANICLE ORGANIZATION1 determines rice inflorescence form through control of cell proliferation in the meristem.
Two types of branches, rachis branches (i.e. nonfloral) and spikelets (i.e. floral), are produced during rice (Oryza sativa) inflorescence development. We previously reported that the ABERRANT PANICLE ORGANIZATION1 (APO1) gene, encoding an F-box-containing protein orthologous to Arabidopsis (Arabidopsis thaliana) UNUSUAL FLORAL ORGANS, suppresses precocious conversion of rachis branch meristems to spikelets to ensure generation of certain number of spikelets. Here, we identified four dominant mutants producing an increased number of spikelets and found that they are gain-of-function alleles of APO1. The APO1 expression levels are elevated in all four mutants, suggesting that an increase of APO1 activity caused the delay in the program shift to spikelet formation. In agreement with this result, ectopic overexpression of APO1 accentuated the APO1 gain-of-function phenotypes. In the apo1-D dominant alleles, the inflorescence meristem starts to increase in size more vigorously than the wild type when switching to the reproductive development phase. This alteration in growth rate is opposite to what is observed with the apo1 mutants that have a smaller inflorescence meristem. The difference in meristem size is caused by different rates of cell proliferation. Collectively, these results suggest that the level of APO1 activity regulates the inflorescence form through control of cell proliferation in the meristem.
Ikeda-Kawakatsu
Kyoko
K
Research Institute for Bioresources, Okayama University, Kurashiki, Okayama 710-0046, Japan.
Yasuno
Naoko
N
Oikawa
Tetsuo
T
Iida
Shigeru
S
Nagato
Yasuo
Y
Maekawa
Masahiko
M
Kyozuka
Junko
J
D001483:Base Sequence; D049109:Cell Proliferation; D048430:Cell Shape; D004251:DNA Transposable Elements / Q000235:genetics; D035264:Flowers / Q000166:cytology* / Q000235:genetics*; D018506:Gene Expression Regulation, Plant; D005799:Genes, Dominant; D017343:Genes, Plant; D018519:Meristem / Q000166:cytology* / Q000235:genetics; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional / Q000235:genetics; D050505:Mutant Proteins / Q000302:isolation & purification; D009154:Mutation / Q000235:genetics; D012275:Oryza / Q000166:cytology* / Q000235:genetics*; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics
D004251:DNA Transposable Elements; D050505:Mutant Proteins; D010940:Plant Proteins