title: Transcript profiling of poplar leaves upon infection with compatible and incompatible strains of the foliar rust Melampsora larici-populina.
abstract: To understand key processes governing defense mechanisms in poplar (Populus spp.) upon infection with the rust fungus Melampsora larici-populina, we used combined histological and molecular techniques to describe the infection of Populus trichocarpa x Populus deltoides 'Beaupré' leaves by compatible and incompatible fungal strains. Striking differences in host-tissue infection were observed after 48-h postinoculation (hpi) between compatible and incompatible interactions. No reactive oxygen species production could be detected at infection sites, while a strong accumulation of monolignols occurred in the incompatible interaction after 48 hpi, indicating a late plant response once the fungus already penetrated host cells to form haustorial infection structures. P. trichocarpa whole-genome expression oligoarrays and sequencing of cDNAs were used to determine changes in gene expression in both interactions at 48 hpi. Temporal expression profiling of infection-regulated transcripts was further compared by cDNA arrays and reverse transcription-quantitative polymerase chain reaction. Among 1,730 significantly differentially expressed transcripts in the incompatible interaction, 150 showed an increase in concentration > or =3-fold, whereas 62 were decreased by > or =3-fold. Regulated transcripts corresponded to known genes targeted by R genes in plant pathosystems, such as inositol-3-P synthase, glutathione S-transferases, and pathogenesis-related proteins. However, the transcript showing the highest rust-induced up-regulation encodes a putative secreted protein with no known function. In contrast, only a few transcripts showed an altered expression in the compatible interaction, suggesting a delay in defense response between incompatible and compatible interactions in poplar. This comprehensive analysis of early molecular responses of poplar to M. larici-populina infection identified key genes that likely contain the fungus proliferation in planta. Sequences from the SSH library described in this article can be retrieved in GenBank under accession numbers CT 027996 to CT 029994 and CT 033829.
authors.affiliation: Unité Mixte de Recherche 1136 Institut National de la Recherche Agronomique, and UMR 1137 INRA/Nancy Université Ecophysiologie et Ecologie Forestières, Centre INRA de Nancy, F-54280 Champenoux, France.
authors.forename: Cécile
authors.initials: C
authors.lastname: Rinaldi
authors.forename: Annegret
authors.initials: A
authors.lastname: Kohler
authors.forename: Pascal
authors.initials: P
authors.lastname: Frey
authors.forename: Frédéric
authors.initials: F
authors.lastname: Duchaussoy
authors.forename: Nathalie
authors.initials: N
authors.lastname: Ningre
authors.forename: Arnaud
authors.initials: A
authors.lastname: Couloux
authors.forename: Patrick
authors.initials: P
authors.lastname: Wincker
authors.forename: Didier
authors.initials: D
authors.lastname: Le Thiec
authors.forename: Silvia
authors.initials: S
authors.lastname: Fluch
authors.forename: Francis
authors.initials: F
authors.lastname: Martin
authors.forename: Sébastien
authors.initials: S
authors.lastname: Duplessis
mesh_terms: D001487:Basidiomycota / Q000145:classification / Q000472:pathogenicity / Q000502:physiology*; D020869:Gene Expression Profiling; D018745:Genome, Plant; D006824:Hybridization, Genetic; D007113:Immunity, Innate / Q000235:genetics; D008031:Lignin / Q000378:metabolism; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology*; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D016133:Polymerase Chain Reaction; D032107:Populus / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology; D012333:RNA, Messenger / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D014774:Virulence
chemical_list: D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D008031:Lignin