title: Downy mildew resistance induced by Trichoderma harzianum T39 in susceptible grapevines partially mimics transcriptional changes of resistant genotypes.
abstract: BACKGROUND
  Downy mildew, caused by Plasmopara viticola, is one of the most severe diseases of grapevine and is commonly controlled by fungicide treatments. The beneficial microorganism Trichoderma harzianum T39 (T39) can induce resistance to downy mildew, although the molecular events associated with this process have not yet been elucidated in grapevine. A next generation RNA sequencing (RNA-Seq) approach was used to study global transcriptional changes associated with resistance induced by T39 in Vitis vinifera Pinot Noir leaves. The long-term aim was to develop strategies to optimize the use of this agent for downy mildew control.
  
  
  RESULTS
  More than 14.8 million paired-end reads were obtained for each biological replicate of T39-treated and control leaf samples collected before and 24 h after P. viticola inoculation. RNA-Seq analysis resulted in the identification of 7,024 differentially expressed genes, highlighting the complex transcriptional reprogramming of grapevine leaves during resistance induction and in response to pathogen inoculation. Our data show that T39 has a dual effect: it directly modulates genes related to the microbial recognition machinery, and it enhances the expression of defence-related processes after pathogen inoculation. Whereas several genes were commonly affected by P. viticola in control and T39-treated plants, opposing modulation of genes related to responses to stress and protein metabolism was found. T39-induced resistance partially inhibited some disease-related processes and specifically activated defence responses after P. viticola inoculation, causing a significant reduction of downy mildew symptoms.
  
  
  CONCLUSIONS
  The global transcriptional analysis revealed that defence processes known to be implicated in the reaction of resistant genotypes to downy mildew were partially activated by T39-induced resistance in susceptible grapevines. Genes identified in this work are an important source of markers for selecting novel resistance inducers and for the analysis of environmental conditions that might affect induced resistance mechanisms.
authors.affiliation: IASMA Research and Innovation Centre, Fondazione Edmund Mach, Via E, Mach 1, 38010, San Michele all'Adige (TN), Italy. michele.perazzolli@fmach.it
authors.forename: Michele
authors.initials: M
authors.lastname: Perazzolli
authors.forename: Marco
authors.initials: M
authors.lastname: Moretto
authors.forename: Paolo
authors.initials: P
authors.lastname: Fontana
authors.forename: Alberto
authors.initials: A
authors.lastname: Ferrarini
authors.forename: Riccardo
authors.initials: R
authors.lastname: Velasco
authors.forename: Claudio
authors.initials: C
authors.lastname: Moser
authors.forename: Massimo
authors.initials: M
authors.lastname: Delledonne
authors.forename: Ilaria
authors.initials: I
authors.lastname: Pertot
mesh_terms: D002874:Chromosome Mapping; D060467:Disease Resistance / Q000235:genetics*; D017343:Genes, Plant / Q000235:genetics; D005838:Genotype; D059014:High-Throughput Nucleotide Sequencing; D058977:Molecular Sequence Annotation; D044742:Peronospora / Q000502:physiology*; D010935:Plant Diseases / Q000276:immunology* / Q000469:parasitology; D017423:Sequence Analysis, RNA; D014158:Transcription, Genetic; D014242:Trichoderma / Q000502:physiology*; D027843:Vitis / Q000235:genetics* / Q000276:immunology / Q000382:microbiology / Q000469:parasitology