Study : Rpv3-1 Locus Mediated Resistance to Grapevine Downy Mildew is Associated with Specific Host Transcriptional Responses and the Accumulation of Stilbenes
Rpv3-1 Locus Mediated Resistance to Grapevine Downy Mildew is Associated with Specific Host Transcriptional Responses and the Accumulation of Stilbenes
European grapevine cultivars (Vitis vinifera spp.) are highly susceptible to the downy mildew pathogen Plasmopara viticola. Breeding of resistant V. vinifera cultivars is a promising strategy to reduce the impact of disease management. Most cultivars that have been bred for resistance to downy mildew, rely on resistance mediated by the Rpv3 (Resistance to P. viticola) locus. However, despite the extensive use of this locus, little is known about the mechanism of Rpv3-mediated resistance. In this study, Rpv3-mediated defense responses were studied in Rpv3+ and Rpv3ˉ grapevine cultivars following inoculation with two distinct P. viticola isolates avrRpv3+ and avrRpv3ˉ, with the latter being able to overcome Rpv3 resistance. Based on comparative microscopic, metabolomic and transcriptomic analyses, our results show that the Rpv3-mediated resistance is associated with a defense mechanism that triggers synthesis of fungi-toxic stilbenes and programmed cell death (PCD), resulting in reduced but not suppressed pathogen growth and development. Functional annotation of the encoded protein sequence of genes significantly upregulated during the Rpv3-mediated defense response revealed putative roles in pathogen recognition, signal transduction and defense responses. Overall design: Gene expression profiles of a susceptible and a resitant grapevine cultivars in response to downy mildew infection at 6 hours post inoculation were generated by RNA-Seq, in duplicates.