The objective of this proposal is to expand the analysis of a gene that is required for the initiation of trichome differentiation. This gene, GL1, was isolated and initially characterized during the previous granting period. It was found that the predicted polypeptide encoded by GL1 is homologous to the Myb class of transcriptional activators. Interestingly, the gene appears to be expressed in stipules, which develop at the base of the leaves, but not in leaf primordia where trichomes develop. This result suggests that GL1 may be involved in the production of a diffusible signal that activates trichome formation. Experiments are proposed to confirm or negate the stipule-derived, trichome morphogen hypothesis. The PI also examine the mechanism behind the reduction in trichome formation that is found in plants that contain a 35S-GL1 gene. Other experiments are designed to identify the sequences that mediate the temporal and spatial regulation of GL1, to begin to identify genes that encode proteins that interact with GL1 promoter or that directly interact with the GL1 protein. In addition, experiments are planned to determine if GL1 is regulated appropriately in other plant species and to begin the characterization of other members of the Arabidopsis myb gene family.
