Identification of a novel mutant allele, fzp‐15, involved in panicle branch pattern of rice (Oryza sativa)

Abstract

FRIZZY PANICLE (FZP) is involved in the development of panicle branching in rice. Herein, a novel mutant fzp‐15, demonstrating the sequential rounds of branching and severe defects in SM (spikelet meristem) formation, was identified. Map‐based cloning revealed that the abnormal panicle architecture of fzp‐15 resulted from an amino acid substitution (Glu (E) to Ala (A)) in the N‐terminal ERF domain of rice FZP protein. To generate new advantageous FZP alleles increasing grain numbers, CRISPR/Cas9 multiplex editing system was used to target the 5’ untranslation region (UTR) of FZP in 'Nipponbare' (NIP). The 85‐bp (−156 to ‐72 bp) or 149‐bp (−157 to ‐9 bp) deletion in the upstream region of FZP can significantly increase grain numbers without a decrease in grain size, while the 38‐bp deletion (−44 to −7 bp) in the upstream region of FZP has little effect in changing grain numbers. These results indicated that the 113‐bp fragment (−157 to −45 bp) upstream of FZP is important to its function and deletion of this region can be used to increase grain numbers in rice.