title: Melampsora larici-populina transcript profiling during germination and timecourse infection of poplar leaves reveals dynamic expression patterns associated with virulence and biotrophy.
abstract: Melampsora larici-populina is responsible for poplar leaf rust disease and causes severe epidemics in poplar plantations in Europe. The poplar rust genome has been recently sequenced and, in order to find the genetic determinants associated with its biotrophic lifestyle, we generated a whole-genome custom oligoarray and analyzed transcript profiles of M. larici-populina during the infection timecourse in poplar leaves. Different stages were investigated during the asexual development of the rust fungus, including resting and germinating urediniospores and seven in planta stages in the telial host. In total, 76% of the transcripts were detected during leaf infection as well as in urediniospores, whereas 20% were only detected in planta, including several transporters and many small secreted proteins (SSP). We focused our analysis on gene categories known to be related to plant colonization and biotrophic growth in rust pathogens, such as SSP, carbohydrate active enzymes (CAZymes), transporters, lipases, and proteases. Distinct sets of SSP transcripts were expressed all along the infection process, suggesting highly dynamic expression of candidate rust effectors. In contrast, transcripts encoding transporters and proteases were mostly expressed after 48 h postinoculation, when numerous haustoria are already formed in the leaf mesophyll until uredinia formation, supporting their role in nutrient acquisition during biotrophic growth. Finally, CAZymes and lipase transcripts were predominantly expressed at late stages of infection, highlighting their importance during sporulation.
authors.affiliation: Institut National de la Recherche Agronomique, Champenoux, France. duplessi@nancy.inra.fr
authors.forename: Sébastien
authors.initials: S
authors.lastname: Duplessis
authors.forename: Stéphane
authors.initials: S
authors.lastname: Hacquard
authors.forename: Christine
authors.initials: C
authors.lastname: Delaruelle
authors.forename: Emilie
authors.initials: E
authors.lastname: Tisserant
authors.forename: Pascal
authors.initials: P
authors.lastname: Frey
authors.forename: Francis
authors.initials: F
authors.lastname: Martin
authors.forename: Annegret
authors.initials: A
authors.lastname: Kohler
mesh_terms: D001487:Basidiomycota / Q000201:enzymology / Q000235:genetics* / Q000472:pathogenicity / Q000502:physiology*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D015966:Gene Expression Regulation, Fungal; D020411:Oligonucleotide Array Sequence Analysis; D010935:Plant Diseases / Q000382:microbiology*; D018515:Plant Leaves / Q000382:microbiology*; D032107:Populus / Q000382:microbiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013172:Spores, Fungal / Q000502:physiology
chemical_list: D005656:Fungal Proteins