Trial to screen for brassinosteroid signaling mutant from Arabidopsis activation-tag lines.

Abstract

Brassinosteroids are steroid hormones that play an essential role in plant growth and development. Brz (brassinazole) is the first specific inhibitor for brassinosteroid biosynthesis. Target of Brz220 is the cytochrome P450 enzyme encoded by DWF4. In the light, plants treated with Brz220 display dwarfism with the dark-green leaves. In the dark, Brz causes deetiolation phenotype with short hypocotyls and open cotyledons, similar to those of BR-deficient mutants. We tried to screen hypocotyl-elongation mutants in the dark with Brz, which can be anticipated as brassinosteroid signaling-accelerated mutants. As a result, we identified Brz insensitive mutant bil1 from EMS-mutation lines, and bil5 from fast neutron-mutation lines. In order to clarify in detail the mechanisms of brassinosteroid signal transduction, we are trying to screen new bil mutants from Arabidopsis activation-tag lines.