title: Influence of evaporative demand on aquaporin expression and root hydraulics of hybrid poplar.
abstract: When light levels and evaporative demand increase, dynamic physiological changes in roots may be required to restore the water balance at the whole plant level. We hypothesized that a dynamic increase in root hydraulic conductance (L(P)) and aquaporin (AQP) expression could moderate the transpiration-induced drop in water potential (Ψ), allowing continued gas exchange in hybrid poplar (Populus trichocarpa × deltoides) saplings. Fifty-six AQPs have been identified in poplar, but little information about their expression patterns in roots is available, especially from a whole-plant water relations perspective. We measured AQP expression and L(P) in plants subjected to different levels of light and evaporative demand. Shaded plants had only one-tenth the root area of plants growing at higher light levels. Shade-grown saplings experiencing a sudden increase in light exhibited a threefold higher L(P) than plants remaining in shade. This dynamic increase in L(P) corresponded with increased transcript abundance of 15 AQPs out of a total of 33 genes simultaneously assessed by quantitative RT-PCR. The tissue-level localization of transcripts of four AQPs was studied with in situ hybridization. Comprehensive expression profiling in conjunction with physiological and morphological measurements is a valuable reference for future studies on AQP function in poplar.
authors.affiliation: Department of Renewable Resources, 442 ESB, University of Alberta, Edmonton, AB, Canada T6E 2E3.
authors.forename: Adriana M
authors.initials: AM
authors.lastname: Almeida-Rodriguez
authors.forename: Uwe G
authors.initials: UG
authors.lastname: Hacke
authors.forename: Joan
authors.initials: J
authors.lastname: Laur
mesh_terms: D000064:Acclimatization; D020346:Aquaporins / Q000235:genetics / Q000378:metabolism*; D055592:Biophysical Phenomena; D002678:Chimera; D018506:Gene Expression Regulation, Plant; D017403:In Situ Hybridization; D008027:Light; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000502:physiology; D032107:Populus / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D012333:RNA, Messenger; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D020346:Aquaporins; D010940:Plant Proteins; D012333:RNA, Messenger