Abstract
The number of grains per panicle significantly contributes to rice yield, but the regulatory mechanism remains largely unknown. Here, we reported a loss-of-function mutant, panicle apical abortion 7 (paa7), which exhibited panicle abortion and degeneration of spikelets on the apical panicles during the late stage of young panicle development in rice. High accumulations of H2O2 in paa7 caused programmed cell death (PCD) accompanied by nuclear DNA fragmentation in the apical spikelets. Map-based cloning revealed that the 3 bp "AGC" insertion and 4 bp "TCTC" deletion mutation of paa7 were located in the 3'-UTR regions of LOC_Os07g47330, which was confirmed through complementary assays and overexpressed lines. Interestingly, LOC_Os07g47330 is known as FRIZZY PANICLE (FZP). Thus, PAA7 could be a novel allele of FZP. Moreover, the severe damage for panicle phenotype in paa7/lax2 double mutant indicated that PAA7 could crosstalk with Lax Panicle 2 (LAX2). These findings suggest that PAA7 regulates the development of apical spikelets and interacts with LAX2 to regulate panicle development in rice.