Abstract
Brassinosteroids (BRs) are steroid hormones of plants that regulate plant growth and development. BRs bind to leucine-rich repeat kinase BRASSINOSTEROID-INSENSITIVE 1 (BRI1) localized to the plasma membrane, activate transcription factors in collaboration with cytosolic kinases and phosphatases, and regulate BR-responsive gene expression, but the details regarding the BR signaling pathway from perception to nuclear events remain unknown. To identify additional components involved in BR signal, we had analyzed various dwarf and semidwarf mutants from Arabidopsis mutant, which is insensitive to the BR synthetic inhibitor Brz. Brz causes deetiolation and dwarf phenotype similar to those of BR-deficient mutants. We had tried to screen mutants that showed to etiolate on medium containing Brz. Here we identify a bil4 (Brz-insensitive-long hypocotyl 4) mutant from activation tagging line. bil4 mutant exhibited outwardly curving, narrow leaves and shorter, thinner inflorescences. From genetic and functional analyses to bil4 mutant, we would like to clarify in detail the mechanism of brassinosteroid signaling transduction.
