Abstract
SummaryPlant pathogens secrete effector molecules during host invasion to promote colonization. However, some of these effectors become recognized by host receptors to mount a defence response and establish immunity. Recently, a novel resistance was identified in wild tomato, mediated by the single dominant V2 locus, to control strains of the soil‐borne vascular wilt fungus Verticillium dahliae that belong to race 2. With comparative genomics of race 2 strains and resistance‐breaking race 3 strains, we identified the avirulence effector that activates V2 resistance, termed Av2. We identified 277 kb of race 2‐specific sequence comprising only two genes encoding predicted secreted proteins that are expressed during tomato colonization. Subsequent functional analysis based on genetic complementation into race 3 isolates and targeted deletion from the race 1 isolate JR2 and race 2 isolate TO22 confirmed that one of the two candidates encodes the avirulence effector Av2 that is recognized in V2 tomato plants. Two Av2 allelic variants were identified that encode Av2 variants that differ by a single acid. Thus far, a role in virulence could not be demonstrated for either of the two variants.
Highlights
In nature, plants are continuously threatened by potential plant pathogens
pathogen- or microbe-associated molecular patterns (P/MAMPs) are perceived by cell surfacelocalized pattern recognition receptors (PRRs) to trigger pattern-triggered immunity (PTI), while effectors are recognized by cytoplasmic receptors that are known as resistance (R) proteins to activate effector-triggered immunity (ETI) (Jones and Dangl, 2006)
To identify Av2 as the V. dahliae gene that mediates avirulence on tomato V2 plants, we pursued a comparative genomics strategy by searching for genomic regions that are absent from all race 3 strains
Summary
Plants are continuously threatened by potential plant pathogens. most plants are resistant to most potential plant pathogens due to an efficient immune system that becomes activated by any type of molecular pattern that accurately betrays microbial invasion (Dangl and Jones, 2001; Cook et al, 2015). The recognition by plants of Avrs and of non-race-specific elicitors, presently known as pathogen- or microbe-associated molecular patterns (P/MAMPs), was combined in the ‘zig-zag’ model (Jones and Dangl, 2006). In this model, P/MAMPs are perceived by cell surfacelocalized pattern recognition receptors (PRRs) to trigger pattern-triggered immunity (PTI), while effectors are recognized by cytoplasmic receptors that are known as resistance (R) proteins to activate effector-triggered immunity (ETI) (Jones and Dangl, 2006). A more recent model, termed the invasion model, recognizes that the functional separation of
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