title: Putative role of aquaporins in variable hydraulic conductance of leaves in response to light.
abstract: Molecular and physiological studies in walnut (Juglans regia) are combined to establish the putative role of leaf plasma membrane aquaporins in the response of leaf hydraulic conductance (K(leaf)) to irradiance. The effects of light and temperature on K(leaf) are described. Under dark conditions, K(leaf) was low, but increased by 400% upon exposure to light. In contrast to dark conditions, K(leaf) values of light-exposed leaves responded to temperature and 0.1 mm cycloheximide treatments. Furthermore, K(leaf) was not related to stomatal aperture. Data of real-time reverse transcription-polymerase chain reaction showed that K(leaf) dynamics were tightly correlated with the transcript abundance of two walnut aquaporins (JrPIP2,1 and JrPIP2,2). Low K(leaf) in the dark was associated with down-regulation, whereas high K(leaf) in the light was associated with up-regulation of JrPIP2. Light responses of K(leaf) and aquaporin transcripts were reversible and inhibited by cycloheximide, indicating the importance of de novo protein biosynthesis in this process. Our results indicate that walnut leaves can rapidly change their hydraulic conductance and suggest that these changes can be explained by regulation of plasma membrane aquaporins. Model simulation suggests that variable leaf hydraulic conductance in walnut might enhance leaf gas exchanges while buffering leaf water status in response to ambient light fluctuations.
authors.affiliation: Unité Mixte de Recherche 547, Physiologie Intégrée de l'Arbre Fruitier et Forestier, Institut National de la Recherche Agronomique, 63039 Clermont-Ferrand, France.
authors.forename: Hervé
authors.initials: H
authors.lastname: Cochard
authors.forename: Jean-Stéphane
authors.initials: JS
authors.lastname: Venisse
authors.forename: Têtè Sévérien
authors.initials: TS
authors.lastname: Barigah
authors.forename: Nicole
authors.initials: N
authors.lastname: Brunel
authors.forename: Stéphane
authors.initials: S
authors.lastname: Herbette
authors.forename: Agnès
authors.initials: A
authors.lastname: Guilliot
authors.forename: Melvin T
authors.initials: MT
authors.lastname: Tyree
authors.forename: Soulaiman
authors.initials: S
authors.lastname: Sakr
mesh_terms: D020346:Aquaporins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D003513:Cycloheximide / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant; D031324:Juglans / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D008027:Light; D018515:Plant Leaves / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D010940:Plant Proteins / Q000502:physiology*; D018526:Plant Transpiration; D012333:RNA, Messenger / Q000378:metabolism; D013696:Temperature; D014867:Water / Q000378:metabolism*
chemical_list: D020346:Aquaporins; D010940:Plant Proteins; D012333:RNA, Messenger; D014867:Water; D003513:Cycloheximide