BnaC03.BIN2 regulates plant height by affecting the main inflorescence length and first effective branch height in Brassica napus L.

Rapeseed (Brassica napus L.) is one of the main oil crops in the world, and increasing its yield is of great significance for ensuring the safety of edible oil. Presently, improving rapeseed plant architecture is an effective way to increase rapeseed yield with higher planting density. However, the regulatory mechanism of rapeseed plant architecture is poorly understood. In this study, a dwarf rapeseed mutant dwarf08 (df08) is obtained by ethyl methane sulfonate (EMS)-mutagenesis. The decrease in plant height of df08 is mainly caused by the reduction in main inflorescence length and first effective branch height and controlled by a single semi-dominant gene. The hybrid plants (F₁) show a semi-dwarf phenotype. Through map-based cloning and transgenic assay, we confirm that the nonsynonymous single nucleotide variant (SNV) (C to T) in BnaC03.BIN2, which is homologous with Arabidopsis (Arabidopsis thaliana) BIN2, is responsible for the dwarfism of df08. BnaC03.BIN2 interacts with BnaBZR1/BES1 and involves in brassinosteroids (BRs) signal transduction. Proline to Leucine substitution in 284 (P284L) enhances the protein stability of BnaC03.bin2-D, disrupts BRs signal transduction and affects the expression of genes regulating cell division, leading to dwarfism of df08. This study provides a new insight for the mechanism of rapeseed plant height regulation and creates an elite germplasm that can be used for genetic improvement of rapeseed architecture.