Research Interests
Cell and molecular biology. Understand plant growth, development, adaptation and reproduction through studies of membrane transport.
Membrane transport is essential for almost all cellular processes, and disruption often results in disease or death. New information, emerging from the study of completed genomes, has revealed a surprising degree of conservation of structure of many important membrane transporter families. Yet we do not know the substrates and mode of action of most membrane transporters, their regulation, and their impact on cellular and organ function. Model systems have several advantages. The genomes have been sequenced, and they can be genetically manipulated, thus simplifying the study of those transporters that are conserved among organisms. We are using plants and yeast to identify key transporters and to understand how organisms sense and respond to changes in nutrients and toxic compounds in the cell or in the environment.
The essential functions of Ca2+ depend on the spatial and temporal distribution of this ion within each cell. The dynamic changes of this ion within the cytosol and internal stores suggest that Ca channels and pumps are diverse and tightly regulated. Of multiple Ca-ATPases in Arabidopsis, only a few have been characterized. Major goals are to (1) identify and characterize Ca pumps after functional expression of plant genes in yeast mutants; (2) understand how expression and activity of transporters are regulated, and (3) understand the in vivo functions in plants. T-DNA disrupted mutants of pumps are being identified, thus allowing us to test for the first time whether growth, signaling responses, and male fertility are impaired. Proton pumps occupy a prominent position among all transporters in plants and yeast. Without the primary motive force to energize coupled carriers or ion channels, all other transport, and thus life, would cease. In spite of this, it is not understood how proton pumps are integrated into the signal transduction networks that govern growth and adaptation. A major proton pump (vacuolar H+-ATPase) acidifies the vacuole and endomembrane compartments, and provides the driving force for transport of many ions and metabolites across the vacuolar membrane. Novel H+-coupled cation transporters were uncovered in plant genomes, though their functions are largely unknown. A working model is that H+ pumps and monovalent cation/H+ exchangers (CHX) affect development, reproduction and tolerance to stress through their effect on endomembrane trafficking. One goal is to understand these functions at the biochemical and cellular level using a combination of biochemical, cellular, molecular, genetic and genomic tools. (The research programs have been supported by the National Science Foundation, USDA and the Department of Energy.)
Education
- Ph.D. Purdue University, 1975
