The objective of this proposal is to characterize the expression and distribution of an excreted phosphate starvation inducible (epsi) acid phosphatase. Specific prioritized goals of the proposal are: 1. To isolate cDNA and genomic clones of the epsi- APase. 2. To characterize the regulation of epsi-APase mRNA during induction by Pi starvation. 3. To study, via immunological methods, the expression and distribution of the epsi-APase in plant cells and whole plants in the presence and absence of phosphate. My laboratory has shown that, in tomato, phosphate starvation inducible (psi) metabolism involves changes in gene expression, protein synthesis, protein secretion, ion transport and biomass distribution. Therefore, (psi) metabolism provides an excellent system with which to study the interactive and pleiotropic regulatory events that govern the relationship between gene expression and metabolism. One of the most dramatic psi responses is the synthesis and secretion of a specific acid phosphatase (APase). Cloning the epsi-APase gene(s) is an essential first step towards understanding psi metabolism in higher plants. We now have all the experimental tools necessary to conduct the proposed research including methods for large scale isolation and purification of APase, several highly sensitive enzyme activity assays and cDNA libraries synthesized from message isolated from cells at various stages of Pi starvation. Plants try to maintain a homeostatic cellular environment despite great variations in the external environment. One important aspect of external variations is the availability of essential mineral nutrients in the soil. In response to shortages of essential nutrients, plants respond in many ways both to reduce the demand for such nutrients and to increase the capacity of the plant to scavenge nutrients from the environment. It is of great interest and importance to know how nutrient shortages are perceived and how plants respond to alleviate the problem. This proposal focuses on how higher plants respond to shortages of the essential element phosphorous. Results from this work will help us in understanding how various responses to nutrient stress are initiated and coordinated.//
