The essential functions of Ca2+ depend on the spatial and temporal distribution of this ion within each cell.  The dynamic changes of Ca within the cytosol and internal stores suggest that Ca channels and pumps are diverse and tightly regulated.  Of the 14 Ca-ATPases in Arabidopsis, only a few have been characterized.  Major goals are (1) to 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 are being identified, thus allowing us to test for the first time whether growth, signaling and responses to stress are impaired.

Proton pumps occupy a prominent position among 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.  Among other functions, this pump has been implicated in morphogenesis, and tolerance to salt and drought stress.  A long term goal is to understand these functions at the biochemical and cellular level.  The laboratory is using a combination of biochemical, biophysical, immunological, molecular and genetic tools.