Abstract
Trichomes (epidermal hairs) function as a physical barrier against herbivores in Arabidopsis thaliana. Furthermore, wounded plants develop new leaves with increased trichome density. Such up-regulation of trichome density is dependent on both wound-inducible biosynthesis, and SCFCOI1 complex-mediated signaling of jasmonic acid. We developed a sensitized genetic screening to obtain mutants specifically defective in plastic regulation of trichome density. Here we report the characterization of a mutant, unarmed9 (urm9). urm9 could not normally increase their trichome density in response to wounding or jasmonic acid treatment. urm9 exhibited otherwise normal response to jasmonic acid, such as accumulation of anthocyanin pigment, supporting that URM9 gene is specifically involved in the regulation of trichome density. Double mutant analyses indicated that URM9 acts as a positive regulator of trichome differentiation in concert with GL1, GL3, and TTG1. Map based approach to clone URM9 is underway.
