LAUSR

Abstract Inflorescence structure of rice, including the number and length of branches, and the density of the spikelet, can greatly affect the number of grains per panicle, which is one of the key factors in yield compositions. Here we identified five allelic mutants sb1-1/2/3/4/5 that related to branch development of rice. In these mutants, the branch meristem fate was prolonged sharply, resulting in delay of transition from branches to spikelets, and then increased the numbers of branches and spikelets per panicle. SB1 encodes a nuclear RING-like domain protein of SHI/LRP/SRS family and strongly expressed in branch meristems. The results of protein interaction and chromatin immunoprecipitation further suggested that SB1 directly repressed the expression of DEP1, TAW1, MOC1 and IPA1 by interacting with a co-repressor complex to affect acetylation level of histone H3 on target regions. Thus, we proposed that SB1 is a transcription repressor of branch meristem activity by widely and negatively regulating a series of genes that maintain branch meristem fate.