Transcription factor OsWRKY72 controls rice leaf angle by regulating LAZY1-mediated shoot gravitropism

Abstract

Leaf angle is a major trait of ideal architecture, which is considered to influence rice (Oryza sativa) cultivation and grain yield. Although a few mutants with altered rice leaf inclination angle have been reported, the underlying molecular mechanism remains unclear. In this study, we showed that a WRKY transcription factor gene, OsWRKY72, was highly expressed in the leaf sheath and lamina joint. Phenotypic analyses showed that oswrky72 mutants have smaller leaf angles than the wild type (WT), while OsWRKY72 overexpression lines exhibited increased leaf angle. This observation suggests that OsWRKY72 functions as a positive regulator, promoting the enlargement of the leaf angle. Our bioinformatics analysis identified LAZY1 as the downstream gene of OsWRKY72. Electrophoretic mobility shift assays (EMSA) and dual luciferase analysis revealed that OsWRKY72 directly inhibits LAZY1 by binding to its promoter. Moreover, knocking out OsWRKY72 enhanced shoot gravitropism, which is in contrast to the phenotype of lazy1 plants. These results imply that OsWRKY72 regulates leaf angle through gravitropism by reducing the expression of LAZY1. In addition, OsWRKY72 could directly regulate the expression of other leaf angle-related genes, such as FLOWERING LOCUS T-LIKE 12 (OsFTL12) and WALL-ASSOCIATED KINASE 11 (OsWAK11). Our study indicates that OsWRKY72 contributes positively to the expansion of the leaf angle by interfering with shoot gravitropism in rice.