title: Responses of hybrid aspen over-expressing a PIP2;5 aquaporin to low root temperature.
abstract: Aquaporins mediate the movement of water across cell membranes. Plasma membrane intrinsic protein 2;5 from Populus trichocarpa×deltoides (PtdPIP2;5) was previously demonstrated to be a functionally important water conducting aquaporin. To study the relevance of aquaporin-mediated root water transport at low temperatures, we generated transgenic Populus tremula×alba over-expressing PtdPIP2;5 under control of the maize ubiquitin promoter, and compared the physiological responses and water transport properties of the PtdPIP2;5 over-expressing lines (PtdPIP2;5ox) with wild-type plants. We hypothesized that over-expression of PtdPIP2;5 would reduce temperature sensitivity of root water transport and gas exchange. Decreasing root temperatures to 10 and 5°C significantly decreased hydraulic conductivities (Lp) in wild-type plants, but had no significant effect on Lp in PtdPIP2;5ox plants. Recovery of Lp in the transgenic lines returned to 20°C from 5°C was faster than in the wild-type plants. Low root temperature did not induce major changes in transcript levels for other PIPs. When roots were exposed to 5°C in solution culture and shoots were exposed to 20°C, wild-type plants had significantly lower net photosynthetic and transpiration rates compared to PtdPIP2;5ox plants. Taken together, our results demonstrate that over-expression of PtdPIP2;5 in P. tremula×alba was effective in alleviating the effects of low root temperature on Lp and gas exchange.
authors.affiliation: Department of Renewable Resources, University of Alberta, Edmonton, AB, Canada.
authors.forename: Kapilan
authors.initials: K
authors.lastname: Ranganathan
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada.
authors.forename: Walid
authors.initials: W
authors.lastname: El Kayal
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada.
authors.forename: Janice E K
authors.initials: JE
authors.lastname: Cooke
authors.affiliation: Department of Renewable Resources, University of Alberta, Edmonton, AB, Canada. Electronic address: jzwiazek@ualberta.ca.
authors.forename: Janusz J
authors.initials: JJ
authors.lastname: Zwiazek
mesh_terms: D020346:Aquaporins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D003080:Cold Temperature; D015870:Gene Expression; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000502:physiology; D018520:Plant Shoots / Q000235:genetics / Q000502:physiology; D018526:Plant Transpiration / Q000502:physiology*; D032107:Populus / Q000235:genetics / Q000502:physiology*; D011401:Promoter Regions, Genetic / Q000235:genetics; D025801:Ubiquitin / Q000235:genetics; D014867:Water / Q000378:metabolism*; D003313:Zea mays / Q000235:genetics
chemical_list: D020346:Aquaporins; D010940:Plant Proteins; D025801:Ubiquitin; D014867:Water
keywords: Aquaporin; Hydraulic conductivity; Low root temperature; PIP2;5; Water transport