A model for cell-type determination and differentiation in plants.

We are using trichome formation on the plant Arabidopsis thaliana as a model for the study of plant cell determination and differentiation. Several of the genes that are required for trichome formation are defined by mutations. Two mutations, ttg and gl1, prevent the initiation of trichome differentiation. Thus, these mutations define products that are involved in the signalling of trichome determination. Other mutations, gl2, gl3, dis1, and dis2, define genes that are involved in trichome maturation. Our immediate goal has been to isolate the genes defined by these mutations and determine the role that they play in trichome formation. Our general goals are (1) to identify counterparts to these genes that are involved in other cell type determination and differentiation processes; (2) to manipulate cell development by altering the normal expression of these genes; and (3) to determine if this information can be used to improve crop plants. Presently, most of our progress has centered on the GL1 gene, which has been isolated and characterized. We have found that GL1 is a myb-related gene that is uniquely required for trichome initiation. As in other plants, Arabidopsis has a family of myb-related genes. We are currently investigating the possibility that some of these other myb-related genes are also uniquely required for other types of cell determination events.