Poster: Late and Moved Abstracts

Abs # 1374: Regulation of aquaporin-mediated root water transport in aspen (Populus tremuloides)

Presenter:	Zwiazek, Janusz J., janusz.zwiazek@ualberta.ca
Authors	Zwiazek, Janusz J. (A)   Kamaluddin, Mohammed  (A)   Siemens, J. A. (A)   Voicu, Mihaela C. (A)   Wan, Xianchong  (A)
Affiliations:	(A): University of Alberta

We have studied the role of aquaporins in root water flow regulation of aspen (Populus tremuloides Michx.). Root hydraulic conductivity was strongly linked to root metabolism and was sensitive to both root respiration and protein synthesis inhibitors. In cycloheximide-treated roots, root hydraulic conductivity was inhibited withinn minutes by 85% compared with untreated roots. This inhibition was correlated with a decrease in the expression of a microsomal protein related to the PIP1 aquaporin. The initial response of roots to drought stress was an increase in root hydraulic conductivity followed by a rapid decrease under more severe water deficit conditions. These effects were due to decreased proportion of the cell-to-cell pathway and were likely mediated by the aquaporins. Under low oxygen (hypoxic) conditions, root hydraulic conductivity was severely inhibited and trigerred stomatal closure. However, an application of ethylene to the roots partly reversed these processes. Root hydraulic conductivity and the effect of ABA on root water flow properties were pH-dependent. Possible regulation mechanisms of aquaporin-mediated root water transport through transcriptional and phosphorylation/dephosphorylation processes as well as the role of pH in water flow regulation are discussed.