Panicle Apical Abortion 7 Regulates Panicle Development in Rice ( Oryza sativa L.).

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 H 2 O 2 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.