title: Adaptive mechanisms and genomic plasticity for drought tolerance identified in European black poplar (Populus nigra L.).
abstract: Summer droughts are likely to increase in frequency and intensity across Europe, yet long-lived trees may have a limited ability to tolerate drought. It is therefore critical that we improve our understanding of phenotypic plasticity to drought in natural populations for ecologically and economically important trees such as Populus nigra L. A common garden experiment was conducted using ∼500 wild P. nigra trees, collected from 11 river populations across Europe. Phenotypic variation was found across the collection, with southern genotypes from Spain and France characterized by small leaves and limited biomass production. To examine the relationship between phenotypic variation and drought tolerance, six genotypes with contrasting leaf morphologies were subjected to a water deficit experiment. 'North eastern' genotypes were collected at wet sites and responded to water deficit with reduced biomass growth, slow stomatal closure and reduced water use efficiency (WUE) assessed by Δ(13)C. In contrast, 'southern' genotypes originating from arid sites showed rapid stomatal closure, improved WUE and limited leaf loss. Transcriptome analyses of a genotype from Spain (Sp2, originating from an arid site) and another from northern Italy (Ita, originating from a wet site) revealed dramatic differences in gene expression response to water deficit. Transcripts controlling leaf development and stomatal patterning, including SPCH, ANT, ER, AS1, AS2, PHB, CLV1, ERL1-3 and TMM, were down-regulated in Ita but not in Sp2 in response to drought.
authors.affiliation: Centre for Biological Sciences, University of Southampton, Life Sciences Building, Southampton SO17 1BJ, UK.
authors.forename: Maud
authors.initials: M
authors.lastname: Viger
authors.affiliation: Centre for Biological Sciences, University of Southampton, Life Sciences Building, Southampton SO17 1BJ, UK.
authors.forename: Hazel K
authors.initials: HK
authors.lastname: Smith
authors.affiliation: UMR Ecologie et Ecophysiologie Forestières, INRA NANCY-Lorraine, 54280 Champenoux, France UMR Ecologie et Ecophysiologie Forestière, Université de Lorraine, BP 239, F-54506 Vandoeuvre, France.
authors.forename: David
authors.initials: D
authors.lastname: Cohen
authors.affiliation: Centre for Biological Sciences, University of Southampton, Life Sciences Building, Southampton SO17 1BJ, UK Present address: USDA Forest Service, National Forest Genetics Lab, 2480 Carson Road, Placerville, CA 95667, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Dewoody
authors.affiliation: Centre for Biological Sciences, University of Southampton, Life Sciences Building, Southampton SO17 1BJ, UK.
authors.forename: Harriet
authors.initials: H
authors.lastname: Trewin
authors.affiliation: Ministry of the Flemish Community, Research Institute for Nature and Forest (INBO), Geraardsbergen B-9500, Belgium.
authors.forename: Marijke
authors.initials: M
authors.lastname: Steenackers
authors.affiliation: INRA, Unité de Recherche Amélioration Génétique et Physiologie Forestières, 2163 avenue de la Pomme de Pin, CS 40001 Ardon, 45075 Orléans Cedex 2, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Bastien
authors.affiliation: Centre for Biological Sciences, University of Southampton, Life Sciences Building, Southampton SO17 1BJ, UK g.taylor@soton.ac.uk.
authors.forename: Gail
authors.initials: G
authors.lastname: Taylor
mesh_terms: D000222:Adaptation, Physiological; D018533:Biomass; D015536:Down-Regulation; D055864:Droughts; D005602:France; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D018745:Genome, Plant; D005838:Genotype; D007558:Italy; D010641:Phenotype; D018515:Plant Leaves / Q000254:growth & development; D054046:Plant Stomata; D018526:Plant Transpiration; D032107:Populus / Q000235:genetics* / Q000254:growth & development; D013030:Spain; D013312:Stress, Physiological; D014197:Trees; D014867:Water
chemical_list: D014867:Water
keywords: carbon isotope discrimination (Δ13C); microarray; stomatal number; water deficit