Regulation of Phosphoinositide Metabolism and Early Responses to Osmotic Stress

North Carolina State University, Raleigh NC

Investigators

Abstract

SUMMARY Polyphosphorylated inositol lipids provide a means for plants to transmit signals within and between cells as well as being key regulators of cellular metabolism in their own right. Plants as sessile organisms respond to most environmental stimuli by altering their pattern of growth. Sustained increases in PI metabolism correlate positively with cell elongation in maize pulvini and with pollen tube growth, and yet little is known about the regulation of plant inositol phospholipid biosynthesis. Phosphatidylinositol 4 monophosphate (PtdIns4P) is the most abundant of the polyphosphorylated lipids in plants. Thus the investigator hypothesizes that it is a key regulator of plant signal transduction. There are two genes encoding PtdIns 4-kinase (PtdIns4K), the enzyme that synthesizes PtdIns4P. One isoform, PtdIns4Kalpha, copurifies with F-actin in plants and has a PH (pleckstrin homology) domain. This preliminary results lead to the hypothesis that the PH domain regulates PtdIns4Kalpha activity and coordinates membrane signaling with actin filament formation. The molecular and biochemical tools are available to test these hypotheses. The goals of this project are: 1. To isolate PtdIns4Kalpha knockout mutants of Arabidopsis, to characterize them biochemically and genetically (micro-array profiling) and to monitor their response to osmotic stress; 2. To identify plant proteins which bind specifically to AtPtdIns4Kalpha. These data are essential to understand how plants as sessile organisms use the PI pathway to sense and respond to external stimuli. By identifying proteins that interact with the lipid kinases, this research will begin to build a network of interacting signaling.