title: Comparative transcriptomics of drought responses in Populus: a meta-analysis of genome-wide expression profiling in mature leaves and root apices across two genotypes.
abstract: BACKGROUND
  Comparative genomics has emerged as a promising means of unravelling the molecular networks underlying complex traits such as drought tolerance. Here we assess the genotype-dependent component of the drought-induced transcriptome response in two poplar genotypes differing in drought tolerance. Drought-induced responses were analysed in leaves and root apices and were compared with available transcriptome data from other Populus species.
  
  
  RESULTS
  Using a multi-species designed microarray, a genomic DNA-based selection of probesets provided an unambiguous between-genotype comparison. Analyses of functional group enrichment enabled the extraction of processes physiologically relevant to drought response. The drought-driven changes in gene expression occurring in root apices were consistent across treatments and genotypes. For mature leaves, the transcriptome response varied weakly but in accordance with the duration of water deficit. A differential clustering algorithm revealed similar and divergent gene co-expression patterns among the two genotypes. Since moderate stress levels induced similar physiological responses in both genotypes, the genotype-dependent transcriptional responses could be considered as intrinsic divergences in genome functioning. Our meta-analysis detected several candidate genes and processes that are differentially regulated in root and leaf, potentially under developmental control, and preferentially involved in early and long-term responses to drought.
  
  
  CONCLUSIONS
  In poplar, the well-known drought-induced activation of sensing and signalling cascades was specific to the early response in leaves but was found to be general in root apices. Comparing our results to what is known in arabidopsis, we found that transcriptional remodelling included signalling and a response to energy deficit in roots in parallel with transcriptional indices of hampered assimilation in leaves, particularly in the drought-sensitive poplar genotype.
authors.affiliation: INRA, Nancy Université, UMR1137 Ecologie et Ecophysiologie Forestières, IFR 110 EFABA, F-54280 Champenoux, France.
authors.forename: David
authors.initials: D
authors.lastname: Cohen
authors.forename: Marie-Béatrice
authors.initials: MB
authors.lastname: Bogeat-Triboulot
authors.forename: Emilie
authors.initials: E
authors.lastname: Tisserant
authors.forename: Sandrine
authors.initials: S
authors.lastname: Balzergue
authors.forename: Marie-Laure
authors.initials: ML
authors.lastname: Martin-Magniette
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Lelandais
authors.forename: Nathalie
authors.initials: N
authors.lastname: Ningre
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Renou
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Tamby
authors.forename: Didier
authors.initials: D
authors.lastname: Le Thiec
authors.forename: Irène
authors.initials: I
authors.lastname: Hummel
mesh_terms: D016000:Cluster Analysis; D055864:Droughts; D017753:Ecosystem; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D053263:Gene Regulatory Networks / Q000235:genetics; D017343:Genes, Plant / Q000235:genetics; D005819:Genetic Markers; D018745:Genome, Plant / Q000235:genetics*; D005838:Genotype; D018519:Meristem / Q000235:genetics*; D015201:Meta-Analysis as Topic; D058977:Molecular Sequence Annotation; D009928:Organ Specificity / Q000235:genetics; D018515:Plant Leaves / Q000235:genetics*; D032107:Populus / Q000235:genetics* / Q000502:physiology; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D005819:Genetic Markers