title: Poplar trees reconfigure the transcriptome and metabolome in response to drought in a genotype- and time-of-day-dependent manner.
abstract: BACKGROUND
  Drought has a major impact on tree growth and survival. Understanding tree responses to this stress can have important application in both conservation of forest health, and in production forestry. Trees of the genus Populus provide an excellent opportunity to explore the mechanistic underpinnings of forest tree drought responses, given the growing molecular resources that are available for this taxon. Here, foliar tissue of six water-deficit stressed P. balsamifera genotypes was analysed for variation in the metabolome in response to drought and time of day by using an untargeted metabolite profiling technique, gas chromatography/mass-spectrometry (GC/MS).
  
  
  RESULTS
  Significant variation in the metabolome was observed in response the imposition of water-deficit stress. Notably, organic acid intermediates such as succinic and malic acid had lower concentrations in leaves exposed to drought, whereas galactinol and raffinose were found in increased concentrations. A number of metabolites with significant difference in accumulation under water-deficit conditions exhibited intraspecific variation in metabolite accumulation. Large magnitude fold-change accumulation was observed in three of the six genotypes. In order to understand the interaction between the transcriptome and metabolome, an integrated analysis of the drought-responsive transcriptome and the metabolome was performed. One P. balsamifera genotype, AP-1006, demonstrated a lack of congruence between the magnitude of the drought transcriptome response and the magnitude of the metabolome response. More specifically, metabolite profiles in AP-1006 demonstrated the smallest changes in response to water-deficit conditions.
  
  
  CONCLUSIONS
  Pathway analysis of the transcriptome and metabolome revealed specific genotypic responses with respect to primary sugar accumulation, citric acid metabolism, and raffinose family oligosaccharide biosynthesis. The intraspecific variation in the molecular strategies that underpin the responses to drought among genotypes may have an important role in the maintenance of forest health and productivity.
authors.affiliation: Faculty of Forestry, University of Toronto, 33 Willcocks St., Toronto, ON, M5S 3B2, Canada. erin.hamanishi@utoronto.ca.|Centre for the Analysis of Genome Evolution and Function, University of Toronto, 25 Willcocks St., Toronto, ON, M5S 3B2, Canada. erin.hamanishi@utoronto.ca.
authors.forename: Erin T
authors.initials: ET
authors.lastname: Hamanishi
authors.affiliation: Department of Wood Science, University of British Columbia, 4030-2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada. genoalily@gmail.com.
authors.forename: Genoa L H
authors.initials: GL
authors.lastname: Barchet
authors.affiliation: Department of Wood Science, University of British Columbia, 4030-2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada. rebecca.dauwe@u-picardie.fr.|Current address: Département des sciences agronomiques et écologiques, Université de Picardie Jules Verne, Amiens, 80039 cedex, France. rebecca.dauwe@u-picardie.fr.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Dauwe
authors.affiliation: Department of Wood Science, University of British Columbia, 4030-2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada. shawn.mansfield@ubc.ca.
authors.forename: Shawn D
authors.initials: SD
authors.lastname: Mansfield
authors.affiliation: Faculty of Forestry, University of Toronto, 33 Willcocks St., Toronto, ON, M5S 3B2, Canada. malcolm.campbell@utoronto.ca.|Centre for the Analysis of Genome Evolution and Function, University of Toronto, 25 Willcocks St., Toronto, ON, M5S 3B2, Canada. malcolm.campbell@utoronto.ca.|Department of Cell & Systems Biology, University of Toronto, 25 Willcocks St., Toronto, ON, M5S 3B2, Canada. malcolm.campbell@utoronto.ca.|Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON, M1C 1A4, Canada. malcolm.campbell@utoronto.ca.
authors.forename: Malcolm M
authors.initials: MM
authors.lastname: Campbell
mesh_terms: D016000:Cluster Analysis; D055864:Droughts; D004734:Energy Metabolism / Q000235:genetics; D008401:Gas Chromatography-Mass Spectrometry; D053263:Gene Regulatory Networks; D005838:Genotype; D055442:Metabolome; D032107:Populus / Q000235:genetics / Q000378:metabolism*; D018749:RNA, Plant / Q000032:analysis / Q000302:isolation & purification / Q000378:metabolism; D013997:Time Factors; D059467:Transcriptome
chemical_list: D018749:RNA, Plant