Kinase activity of OsBRI1 is essential for brassinosteroids to regulate rice growth and development

► A classic rice mutant Fn189 is characterized by semi-dwarfism and erect leaf. ► Physiological and morphological assays showed that Fn189 is less sensitive to BRs. ► Fn189 is a novel allelic mutant of the D61 gene encoding the BRs receptor OsBRI1. ► The I834F substitution caused dramatically reduced kinase activity of OsBRI1.