Abstract
Brassinosteroids (BRs) are plant steroid hormones that regulate plant growth and development. To identify detail molecular mechanism of brassinosteroid signaling, we tried to screen mutants from the Arabidopsis activation tagging lines by using Brz (brassinazole), which is the specific inhibitor of brassinosteroid biosynthesis. Brz causes deetioation and dwarf phenotypes that are similar to the phenotypes of BR-deficient mutants. To analyze BR signaling, we tried to screen Brz insensitive mutants bil (Brz-insensitive-long hypocotyl), which showed longer hypocotyls than the wild type with Brz in the dark. Here we identified new bil semidominant mutant bil3 from activation tagging line, which shows longer hypocotyl with Brz at the germination stage, and a slender dwarf phenotype related to excessive epinastic leaves and thin inflorescences at growth stage in the light. In the adult, compared with the wild strain, bil3 shows that the number of inflorescences is about 1.3 times, the number of branches is about 2.2 times, and the number of siliques is about 2.2 times.
