Grapevine DMR6-1 Is a Candidate Gene for Susceptibility to Downy Mildew

Abstract

Grapevine (Vitis vinifera) is a valuable crop in Europe for both economical and cultural reasons, but highly susceptible to Downy mildew (DM). The generation of resistant vines is of critical importance for a sustainable viticulture and can be achieved either by introgression of resistance genes in susceptible varieties or by mutation of Susceptibility (S) genes, e.g., by gene editing. This second approach offers several advantages: it maintains the genetic identity of cultivars otherwise disrupted by crossing and generally results in a broad-spectrum and durable resistance, but it is hindered by the poor knowledge about S genes in grapevines. Candidate S genes are Downy mildew Resistance 6 (DMR6) and DMR6-Like Oxygenases (DLOs), whose mutations confer resistance to DM in Arabidopsis. In this work, we show that grapevine VviDMR6-1 complements the Arabidopsis dmr6-1 resistant mutant. We studied the expression of grapevine VviDMR6 and VviDLO genes in different organs and in response to the DM causative agent Plasmopara viticola. Through an automated evaluation of causal relationships among genes, we show that VviDMR6-1, VviDMR6-2, and VviDLO1 group into different co-regulatory networks, suggesting distinct functions, and that mostly VviDMR6-1 is connected with pathogenesis-responsive genes. Therefore, VviDMR6-1 represents a good candidate to produce resistant cultivars with a gene-editing approach.

Application of the NanoString nCounter System as an Alternative Method to Investigate Molecular Mechanisms Involved in Host Plant Responses to Plasmodiophora brassicae

“…DMR6 , which encodes a putative 2OG-Fe (II) oxygenase, is significantly induced by pathogen or SA treatment and regulates SA homoeostasis by hydroxylating SA into 2,5-DHBA [ 42 ]. It has been a promising target for gene editing as a susceptibility factor to increase plant resistance to broad-spectrum diseases [ 43 , 44 , 45 ]. Multiple B. napus transcripts for DMR6 were upregulated at different time-points in response to P. brassicae pathotypes 5X and 3A [ 34 , 38 ], including the transcript for BnaC07g29940D, which was validated with the NanoString assay ( Figure 2 ).…”

The Role of Italy in the Use of Advanced Plant Genomic Techniques on Fruit Trees: State of the Art and Future Perspectives

“…To produce pathogen-tolerant grape plants, which require lower pesticide treatments, many efforts have been focused on the development of several genome-editing approaches applied on susceptibility genes [ 112 ] and on other important genes involved in the regulation of the responses to biotrophic pathogens [ 113 ]. The loss-of-function mutation, mediated by CRISPR/Cas9, of susceptibility genes to powdery and downy mildew was the most used strategy [ 114 , 115 ]. In parallel, a cisgenic approach was developed to introduce resistance to Plasmopara viticola (RPV3-1 locus) [ 116 ] into elite wine grape cultivars (e.g., Glera, Sangiovese, Chardonnay, and Pinot noir).…”

Vitis vinifera plants edited in DMR6 genes show improved resistance to downy mildew

“…In grapevine, the DMR6-DLO family consists of two highly similar genes ( VviDMR6-1 and VviDMR6-2 ) and three encoding DMR6-like oxygenases ( VviDLO1, 2 and 3 ). A recent analysis of the grapevine DMR6 and DLO networks of transcriptionally co-regulated genes revealed a consistent group of defense-associated genes that are co-regulated with VviDMR6-1 and VviDMR6-2 , and that over-expression of VviDMR6-1 restores susceptibility to DM of the of the Arabidopsis dmr6-1 resistant mutant (Pirrello et al, 2022).…”