Benzothiadiazole‐primed defence responses and enhanced differential expression of defence genes in Vitis vinifera infected with biotrophic pathogens Erysiphe necator and Plasmopara viticola

Abstract

Benzothiadiazole (BTH), a salicylic acid analogue, strengthens plant defence mechanisms against a broad spectrum of pathogens. The role of pre-treatment with BTH in enhancing resistance against infection with various isolates of downy and powdery mildews (Plasmopara viticola and Erysiphe necator) was investigated in grapevine leaves. Tools were developed to better assess the defence status of the plant. In compatible interactions amongst a set of 19 genes, more than 57AE2% of differentiated transcripts from P. viticola infected-leaves (Pv-infected leaves) and 90% from E. necator-infected leaves (En-infected leaves) were down-regulated at 24 h post-inoculation (hpi), indicating a manipulation of host responses by the pathogens. BTH treatment enhanced grapevine defences, with pathogen growth inhibited by 61-98%, depending on the pathogen isolate. Treatment also triggered up-regulation of pathogenesis-related protein genes such as PR-1, PR-2, PR-3, PR-8 and PR-10 in Pv-infected leaves, and PR-3, PR-6 and PR-10 in En-infected leaves. Treatment with BTH also led to regulation of indole pathway transcripts; in particular, anthranilate synthase was down-regulated at 24 hpi in all infected leaves, then strongly up-regulated afterwards according to the rate of pathogen development. Quantitation of polyphenols and stilbenes showed that pterostilbene was specifically accumulated in pre-treated leaves and associated with biological efficacy and significant increases in PR protein gene transcripts. The temporal evolution of defence-related genes in pre-treated infected leaves suggests that grapevine responses vary depending on the inter-or intra-species variability of pathogens.

High-throughput gene-expression quantification of grapevine defense responses in the field using microfluidic dynamic arrays

“…An additional file shows the origin of the sequences and/or references used to find new candidate genes involved in grapevine defenses (Additional file 1). The strategy combines two approaches : the first was based on the comparison of new grapevine genomic data with known grapevine sequences previously selected from pathogen-related studies to which were added genes deployed in two recently developed molecular diagnostic tools (“grapevine - qPFD”, patent INRA FR 1055042/WO/2011/161388, CT/FR2011/051470 - INRA Angers - Brisset MN, [38] and “BioMolChem” chip, [26]). The sequences used in RT-qPCR were blasted against the most recent Vitis vinifera sequences (taxid = 29,760, [41]) using the Blast resource from the National Center for Biotechnology Information (https://blast.ncbi.nlm.nih.gov/Blast.cgi).…”

“…As the expected action of these potentially eliciting products is rather preventive than curative and because preliminary studies [26] showed that the pathogen diverts the plant metabolism in its favor and particular by blocking the deployment of its defenses, we chose a sampling protocol rather early in the season when the period of grapevine sensitivity against downy mildew is the strongest than later after the pathogen inoculation or once the epidemic is in place at a time when there was no real point in tracking the defense status of the vine. The grapevine defense reaction was analyzed 48 h after a second elicitor treatment applied in the vineyard.…”

“…Recently, two molecular diagnostic tools were designed that provide information about the defense status of grapevine: “qPFD” (quantitative RT-PCR microplate/DNA chip low density) which was first developed on the apple scab model ( Malus domestica / Venturia inaequalis ) and extended to grapevine and evaluates a set of nine groups representing 28 target genes (patent INRA WO 2011/161388, CT/FR2011/051470 - INRA Angers - Brisset MN) [38]; and “BioMolChem”chip which is based on 20 marker genes highly involved in grapevine defense mechanisms [26]. However, a more accurate diagnostic tool would certainly require a larger number of defense markers since genomic analyses have shown that induction of the plant immune system is linked to changes in the expression of thousands of genes [39].…”

Impact of abiotic stresses on the protection efficacy of defence elicitors and on metabolic regulation in tomato leaves infected by Botrytis cinerea

“…Based on literature, four agents for which the ability to induce plant defence mechanisms has been previously demonstrated were used here as positive "PDE controls": Bion 50WG®, BABA, Chitosan and methyl jasmonate (MeJA) (Amborabe et al 2004 ;Azami-Sardooei et al 2013 ;Dufour et al 2013 ;Eyre et al 2006 ;Zhu and Tian 2012 ). In addition to those "PDE controls", the protection efficacy against of seven potential PDE were investigated (coded A to G; Table 1 ).…”

“…Among available biocontrol strategies, the induction of resistant mechanisms, notably through the application of plant defence elicitors (PDE), represents a promising alternative to chemical fungicides (Ballester et al 2011 ). PDE can be defined as natural or synthetic compounds with no direct antifungal activity which, by mimicking natural signalling compounds, induce defence mechanisms in plants, in turn resulting in enhanced resistance to pests and pathogens upon attack (Fu and Dong 2013 ;Dufour et al 2013 ). Alternatively, some compounds do not immediately trigger plant defence mechanisms but provide resistance through a faster and/or stronger induction of defence mechanisms following pathogen and pest infection.…”