The regulation of genes involved in trichome development

Abstract

Arabidopsis thaliana is an organism that can be used as a model for most of the processes that occur in flowering plants. The leaf hairs, or trichomes, of Arabidopsis thaliana are macroscopic single cells that have been used as a model system for cell fate determination, cell expansion, cell cycle regulation, cell wall deposition, as well as other processes. Initiation of the trichome cell fate is controlled by a complex of genes including GLABRA1 (GL1), TRANSPARENT TESTA GLABRA (TTG), and GLABRA3 (GL3). This work examines the role of GL3 in trichome initiation and uses plants expressing varying levels of GL3 to determine if genes involved in trichome development are regulated by GL3. Though several genes are given a cursory examination, the regulation of two genes, an α-carbonic anhydrase and a novel cell-cycle regulator called SIAMESE, are given a thorough examination. The α-carbonic anhydrase At2g28210 was previously not known to be involved in trichome development. Its involvement in trichome development was discovered with the aid of an enhancer trap line with robust reporter gene expression in developing trichomes. Pharmacological studies indicate that this α-carbonic anhydrase may play a role in trichome expansion. SIAMESE (SIM) was first identified in a mutant screen in the Larkin lab. This dissertation demonstrates that this gene encodes a novel type of cell-cycle regulator with several homologs in Arabidopsis and other plant species. SIM and one of its homologs in Arabidopsis were shown to be expressed in a trichome-dependent manner. These investigations shed new light into the molecular process of trichome development.