9505687 Sack Stomata consist of two guard cells surrounding a pore that regulates gas exchange through the aerial plant epidermis. Little is known about the genes that regulate stomatal patterning, determination and differentiation. Two recessive Arabidopsis mutants have been isolated, too many mouths (tmm) and four lips (flp), each with extra adjacent stomata. Both affect stomatal production and determination more than patterning or differentiation. ttm appears to affect both precursor cell formation and activity and may be an important regulator of stomatal production. The research proposed has three objectives overall. First, to understand the phenotypes better, Dr. Sack will attempt to: a) isolate new alleles, b) characterize the distribution of the stomatal phenotypes throughout the plant, c) determine whether tmm and flp induce ectopic expression of stomatal genes, d) analyze the extent of pore development in mutants, e) determine whether substomatal placement and size is affected, and f) characterize cell lineages involved in the development of wild type stomata and of stomatal clusters. A second objective is to isolate new mutants and loci affecting stomatal development. The third major objective is to do fine mapping to choose appropriate cloning strategies. These mutants are likely to help answer basic questions of plant cell development such as how cells are selected for specific fates, as well as how differentiation is initiated and executed. In the long term, knowledge of the genetics and molecular biology of stomatal development would be quite valuable given the importance of stomata for plant productivity. ***
