The objective of the proposed research is to identify and characterize cis-acting genetic elements that respond to signals regulating cell-specific gene expression in tissues. Dr. Mets will study the differentiation of bundle sheath and mesophyll cells within the leaves of plants of the genus Flaveria (Compositae) with Ca pathway of photosynthesis. He will characterize the relative levels and patterns of expression of members of the ribulose-1,5-bisphospate carboxylase small subunit multigene family (rbcS genes), expressed only in bundle sheath cells. Agrobacterium mediated transformation will be used to transfer rbcS genes from Ca species (Petunia and Ca or physiologically intermediate species of Flaveria) into Ca plants. Since the rbcS genes from the Ca sources are ordinarily expressed in all of the mesophyll cells of the leaf, he will be interested in seeing if the introduced genes can respond to the cell- specific control signals present in the Ca leaves. This will be studied by separating bundle sheath and mesophyll cells to determine their respective message contents. The board objective of the proposed experiments is to contribute to an understanding of mechanisms that regulate cellular differentiation. The two cell types examined here (bundle sheath and mesophyll cells of the leaves) show numerous qualitative as well as quantitative differences in expression of both nuclear and organellar genes.
