A novel frameshift mutant allele, fzp-10, affecting the panicle architecture of rice

Abstract

The rice FRIZZY PANICLE (FZP) locus on chromosome 7, in which an ERF and acidic domain are present, is concerned with the regulation of spikelet meristem identity and the determination of panicle architecture. Many fzp mutants drastically alter panicle morphology with higher-order rachis-branches developing successively instead of the development of floral organs in these mutants. A new mutant showing the same fzp phenotype was induced by γ-ray irradiation of seeds of a rice cultivar “Gimbozu”. Examination of this fzp-like mutant for its allelism to a known allele of fzp-1, nucleotide sequence, and panicle and agronomic characteristics clearly indicated that the allele of this fzp-like mutant is located in FZP. Because there is a previously identified allele called fzp-9, we designated this new allele as fzp-10. fzp-10 has a single nucleotide (cytosine) deletion between the ERF domain and the acidic domain, which results in a frameshift mutation and a premature stop codon, thereby altering the C-terminus of the encoded protein. The degree of higher-order branching in the panicles was significantly reduced in the fzp-10 mutant compared with that of fzp-1. Moreover, the fzp-10 mutant showed highly depressed culm and panicle lengths and panicle number, as well as delayed heading dates compared with its wild type and also with fzp-1. fzp-10 has several new characteristics, its altered nucleotide position and severity of phenotype alteration, and, therefore, could be a new gene resource to examine the function of FZP and the determination of rice panicle architecture.