Project description:Tiller angle is a key factor determining rice plant architecture, planting density, light interception, photosynthetic efficiency, disease resistance, and grain yield. The distribution of auxin and shoot gravitropism play important roles in regulating tiller angles of rice. Several tiller angle-associated genes have been cloned. However, the mechanisms underlying tiller angle control are far from clear. In this study, we isolate bta1-1, a mutant with an enlarged tiller angle throughout its life cycle. A detailed analysis reveals that BTA1 has multiple functions because several major agronomic traits, including tiller and panicle number, biomass production, secondary branch number per panicle, panicle weight, grain size, and grain weight, are increased in bta1-1 plants. Moreover, BTA1 is a positive regulator of shoot gravitropism in rice. Shoot responses to gravistimulation are disrupted in bta1-1 under both light and dark conditions. Gene cloning reveals that bta1-1 is a novel mutant allele of LA1. LA1 is able to rescue the tiller angle and shoot gravitropism defects observed in bta1-1. BTA1/LA1 is required to regulate the expression of auxin transporters and signaling factors that control shoot gravitropism and tiller angle. High-throughput mRNA sequencing is performed to elucidate the molecular and cellular functions of BTA1/LA1. The results show that BTA1/LA1 may have multiple functions in regulating nucleosome and chromatin assembly, and protein and DNA interactions. Our results provide new insight into the mechanisms whereby BTA1/LA1 controls shoot gravitropism and tiller angle in rice.
