Morphological and molecular characterization of a new frizzy panicle mutant, "fzp-9(t)", in rice (Oryza sativa L.).

The spikelet identity gene "fzp" (frizzy panicle) is required for transformation of the floral meristems to inflorescent shoots. In fzp mutants, spikelets are replaced by branches and spikelet meristems produce massive numbers of branch meristems. We have isolated and characterized a new fzp mutant derived from anther culture lines in rice and designated as fzp-9(t). The fzp-9(t) mutant showed retarded growth habit and developed fewer tillers than those of the wild-type plant. The primary and secondary rachis branches of fzp-9(t) appeared to be normal, but higher-order branches formed continuous bract-like structures without developing spikelets. The genetic segregation of fzp-9(t) showed a good fit to the expected ratio of 3: 1. The sequence analysis of fzp-9(t) revealed that there is a single nucleotide base change upstream of the ERF (ethylene-responsive element-binding factor) domain compare to wild-type plant. The mutation point of fzp-9(t) (W66G) was one of the six amino acids of the ERF domain that contributed to GCC box-specific binding. The premature formation of a stop codon at the beginning of the ERF domain might cause a non-functional product.