Poster: Signaling, cell-to-cell

Abs # 434: Increased tolerance to water stress in transgenic Arabidopsis plants constitutively expressing the type I inositol polyphosphate 5-phosphatase

Presenter:	Perera, Imara Y, imara_perera@ncsu.edu
Authors	Perera, Imara Y (A)   Randall, Candace  (A)   Hung, ChiuYueh  (A)   Boss, Wendy F (A)
Affiliations:	(A): North Carolina State University

In order to attenuate inositol 1,4,5-trisphosphate (InsP₃) signaling we have generated 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. Similarly, in transgenic plants, the InsP 5-ptase is localized to the plasma membrane and basal InsP₃ levels are reduced by 95% compared with wild type. Although the InsP 5-ptase transgenic plants grow normally under optimal growth conditions, they are more tolerant to drought and have a 30% decrease in the rate of water loss compared to wild type plants. Furthermore, the onset of water stress is delayed and the transgenic plants recover more quickly than the wild type after rehydration. No significant differences were detected in the responses of guard cells from wild type and transgenic plants to light or dark treatments. However, guard cells of transgenic plants were more responsive to exogenous ABA and less responsive to Ca²⁺. Although InsP₃ has been implicated in regulating guard cell closure and blocking InsP₃ synthesis has been shown to affect ABA responses, our results show that in this system, dampening InsP₃ did not compromise the ability to respond to ABA. In fact, the guard cells of InsP 5-ptase plants are more responsive to exogenous application of ABA and the induction of ABA-responsive genes is not compromised. We propose that the InsP 5-ptase plants could provide a useful system to dissect the cross talk between parallel signaling pathways and to evaluate the contribution of InsP₃-mediated signaling in plant responses to stress. (supported by NASA).