RESUMEN
Grain number per panicle (GNP) is an important agronomic trait that contributes to rice grain yield. Despite its importance in rice breeding, the molecular mechanism underlying GNP regulation remains largely unknown. In this study, we identified a previously unrecognized regulatory gene that controls GNP in rice, Oryza sativa REPRODUCTIVE MERISTEM 20 (OsREM20), which encodes a B3 domain transcription factor. Through genetic analysis and transgenic validation we found that genetic variation in the CArG box-containing inverted repeat (IR) sequence of the OsREM20 promoter alters its expression level and contributes to GNP variation among rice varieties. Furthermore, we revealed that the IR sequence regulates OsREM20 expression by affecting the direct binding of OsMADS34 to the CArG box within the IR sequence. Interestingly, the divergent pOsREM20IR and pOsREM20ΔIR alleles were found to originate from different Oryza rufipogon accessions, and were independently inherited into the japonica and indica subspecies, respectively, during domestication. Importantly, we demonstrated that IR sequence variations in the OsREM20 promoter can be utilized for germplasm improvement through either genome editing or traditional breeding. Taken together, our study characterizes novel genetic variations responsible for GNP diversity in rice, reveals the underlying molecular mechanism in the regulation of agronomically important gene expression, and provides a promising strategy for improving rice production by manipulating the cis-regulatory element-containing IR sequence.
Asunto(s)
Grano Comestible/genética , Oryza/genética , Oryza/metabolismo , Proteínas de Plantas/metabolismo , Sitios de Carácter Cuantitativo , Alelos , Domesticación , Grano Comestible/crecimiento & desarrollo , Regulación de la Expresión Génica de las Plantas , Genes de Plantas/genética , Secuencias Invertidas Repetidas , Fitomejoramiento/métodos , Proteínas de Plantas/genética , Regiones Promotoras GenéticasRESUMEN
Rice tiller angle is a key agronomic trait that contributes to ideal plant architecture and grain production. LAZY1 (LA1) was previously shown to control tiller angle via affecting shoot gravitropism, but the underlying molecular mechanism remains largely unknown. In this study, we identified an LA1-interacting protein named Brevis Radix Like 4 (OsBRXL4). We showed that the interaction between OsBRXL4 and LA1 occurs at the plasma membrane and that their interaction determines nuclear localization of LA1. We found that nuclear localization of LA1 is essential for its function, which is different from AtLA1, its Arabidopsis ortholog. Overexpression of OsBRXL4 leads to a prostrate growth phenotype, whereas OsBRXLs RNAi plants, in which the expression levels of OsBRXL1, OsBRXL4, and OsBRXL5 were decreased, display a compact phenotype. Further genetic analysis also supported that OsBRXL4 controls rice tiller angle by affecting nuclear localization of LA1. Consistently, we demonstrated that OsBRXL4 regulates the shoot gravitropism through affecting polar auxin transport as did LA1. Taken together, our study not only identifies OsBRXL4 as a regulatory component of rice tiller angle but also provides new insights into genetic regulation of rice plant architecture.