The long-term goal of this research is to understand the molecular machinery responsible for the formation of viable pollen grains. During pollen development, a callose wall is synthesized between the primary cell wall and plasma membrane in the mother cells of pollen and the tetrads of microspores. Callose is also present in mature pollen grains and is the major component of the pollen tube wall. Formation of the callose wall is vital for pollen development and male fertility in flowering plants. Three genetic loci affecting the synthesis of this callose wall have been isolated and characterized in Arabidopsis. Mutations in these genes result in male sterile phenotypes associated with a common defect in reduced callose deposition during pollen formation. They encode a microsporogenesis-specific callose synthase (CalS5), a novel Rhomboid-like protease and a receptor-like protein kinase. The immediate objective of this project is to further characterize the ClaS5 complex and determine whether it is regulated by the protease and protein kinase during pollen formation. The identification of components of the CalS5 complex and regulation of CalS5 by phosphorylation and proteolytic activation will be studied using both biochemical and proteomic approaches. Additional genetic loci involved in callose wall synthesis will be identified and characterized using genetic as well as genomic techniques.
Intellectual Merit: The results anticipated from this research will provide significant new insights into mechanisms by which callose synthesis is regulated at the molecular level, and will also advance our understanding of plant reproduction. This project will add to our understanding of callose synthesis pathways which are not only important in pollen production, but also in host responses to pathogen infection. At the same time, these studies will give us new insights into the functions of Rhomboid-like proteases and receptor-like kinases which until now, have been poorly characterized in plants.
Broader Impacts: The proposed project will provide an opportunity to train graduate students and postdoctoral associates in the areas of biochemistry, and cell and developmental biology in plants. It will also provide a platform to integrate research expertise from other fields and newly developed resources such as glycan arrays into plant research. The PIs laboratory will actively participate in the University-wide outreach programs, and will accept one to two K-12 students and/or high school science teachers for two weeks to three months during each summer. This project will also provide excellent training opportunities for undergraduats who take Biochemistry and Plant Biochemistry courses which the PI teaches to participate in GFP-tagged protein localization, and suppressor screens and mapping projects in the PIs laboratory.
