Poster: Intracellular Signaling
Abs #
841: Up-regulation of phosphoinositide metabolism in plant cells constitutively expressing the type I inositol polyphosphate 5-phosphatase: Altering plant responses to stress.
In order to attenuate inositol 1,4,5-trisphosphate (InsP3) signaling and alter phosphoinositide (PI) metabolism in plants we have generated transgenic tobacco cells and Arabidopsis plants constitutively expressing the human type I inositol polyphosphate 5-phosphatase (InsP 5-ptase) an enzyme that specifically hydrolyzes InsP3. In animal cells, this enzyme is associated with the plasma membrane and is responsible for the rapid degradation of InsP3, effectively terminating a signal. We have shown previously that the transgenic tobacco cells have drastically reduced basal InsP3 levels compared with wild type cells and an increased flux through the phosphoinositide pathway (Perera et al., 2002,Plant Physiology 129: 1795-1806). Although the transgenic Arabidopsis plants expressing InsP 5-ptase grow normally under optimal growth conditions initial studies indicate differences in the response of the plants to gravistimulation and drought stress. The transgenic Arabidopsis plants are more resistant to drought and survive for up to a week after wild type plants have died from lack of water. A comparison of water loss from leaves of wild type and transgenic plants revealed that the transgenic plants had a 35 % decrease in the rate of water loss compared to the wild type plants. Our data suggests that altering phosphoinositide turnover affects the stress responses of the transgenic plants. We anticipate that the InsP 5-ptase expressing plants will provide a good model system for testing the involvement of InsP3-mediated signaling in plant stress responses and for elucidating the downstream events in this signaling pathway.
