title: Vat, an Amazing Gene Conferring Resistance to Aphids and Viruses They Carry: From Molecular Structure to Field Effects.
abstract: We review half a century of research onCucumis meloresistance toAphis gossypiifrom molecular to field levels. TheVatgene is unique in conferring resistance to bothA. gossypiiand the viruses it transmits. This double phenotype is aphid clone-dependent and has been observed in 25 melon accessions, mostly from Asia. It is controlled by a cluster of genes including CC-NLR, which has been characterized in detail. Copy-number polymorphisms (for the whole gene and for a domain that stands out in the LLR region) and single-nucleotide polymorphisms have been identified in theVatcluster. The role of these polymorphisms in plant/aphid interactions remains unclear. TheVatgene structure suggests a functioning with separate recognition and response phases. During the recognition phase, the VAT protein is thought to interact (likely indirectly) with an aphid effector introduced during cell puncture by the aphid. A few hours later, several miRNAs are upregulated inVatplants. Peroxidase activity increases, and callose and lignin are deposited in the walls of the cells adjacent to the stylet path, disturbing aphid behavior. In aphids feeding onVatplants, Piwi-interacting RNA-like sequences are abundant and the levels of other miRNAs are modified. At the plant level, resistance to aphids is quantitative (aphids escape the plant and display low rates of reproduction). Resistance to viruses is qualitative and local. Durability of NLR genes is highly variable.A. gossypiiclones are adapted toVatresistance, either by introducing a new effector that interferes with the deployment of plant defenses, or by adapting to the defenses it triggered. Viruses transmitted in a non-persistent manner cannot adapt toVatresistance. At population level,Vatreduces aphid density and genetic diversity. The durability ofVatresistance toA. gossypiipopulations depends strongly on the agro-ecosystem, including, in particular, the presence of other cucurbit crops serving as alternative hosts for adapted clones in fall and winter. At the crop level,Vatresistance decreases the intensity of virus epidemics whenA. gossypiiis the main aphid vector in the crop environment.
authors.affiliation: Génétique et Amélioration des Fruits et Légumes, INRA Montfavet, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Boissot
authors.affiliation: Pathologie Végétale, INRA Montfavet, France.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Schoeny
authors.affiliation: Centre de Biologie pour la Gestion des Populations, UMR CBGP, INRA Montferrier-sur-Lez, France.
authors.forename: Flavie
authors.initials: F
authors.lastname: Vanlerberghe-Masutti
keywords: Aphis gossypii; Cucumis melo; NLR resistance gene; durability; melon; resistance deployment; resistance to insects; resistance to viruses