ROLES OF THE GLABROUS1 AND TRANSPARENT TESTA GLABRA GENES IN ARABIDOPSIS TRICHOME DEVELOPMENT

Arabidopsis trichomes are branched, single-celled epidermal hairs. The se specialized cells provide a convenient model for investigating the specification of cell fate in plants. Two key genes regulating the ini tiation of trichome development are GLABROUS1 (GL1) and TRANSPARENT TE STA GLABRA (TTG). GL1 is a member of the myb gene family. The maize R gene, which can functionally complement the Arabidopsis ttg mutation, encodes a basic helix-loop-helix protein. We used constitutively expre ssed copies of the GL1 and R genes to test hypotheses about the roles of GL1 and TTG in trichome development. The results support the hypoth esis that TTG and GL1 cooperate at the same point in the trichome deve lopmental pathway. Furthermore, the constitutive expression of bath GL 1 and R in the same plant caused trichomes to develop on all shoot epi dermal surfaces. Results were also obtained indicating that TTG plays an additional role in inhibiting neighboring cells from becoming trich omes.