A Venom Allergen-Like Protein, RsVAP, the First Discovered Effector Protein of Radopholus similis That Inhibits Plant Defense and Facilitates Parasitism

Abstract

Radopholus similis is a migratory endoparasitic nematode that is extremely harmful to host plants. Venom allergen-like proteins (VAPs) are members of the cysteine-rich secretory protein family that are widely present in plants and animals. In this study, we cloned a VAP gene from R. similis, designated as RsVAP. RsVAP contains an open reading frame of 1089 bp encoding 362 amino acids. RsVAP is specifically expressed in the esophageal gland, and the expression levels of RsVAP are significantly higher in juveniles than in other life stages of R. similis. This expression pattern of RsVAP was consistent with the biological characteristics of juveniles of R. similis, which have the ability of infection and are the main infection stages of R. similis. The pathogenicity and reproduction rate of R. similis in tomato was significantly attenuated after RsVAP was silenced. In tobacco leaves transiently expressing RsVAP, the pathogen-associated molecular pattern-triggered immunity (PTI) induced by a bacterial flagellin fragment (flg22) was inhibited, while the cell death induced by two sets of immune elicitors (BAX and Gpa2/RBP-1) was repressed. The RsVAP-interacting, ras-related protein RABA1d (LeRabA1d) was identified in tomato hosts by yeast two-hybrid and co-immunoprecipitation assays. RsVAP may interact with LeRabA1d to affect the host defense response, which in turn facilitates nematode infection. This study provides the first evidence for the inhibition of plant defense response by a VAP from migratory plant-parasitic nematodes, and, for the first time, the target protein of R. similis in its host was identified.

Aphelenchoides besseyi Ab-FAR-1 Interacts with Arabidopsis thaliana AtADF3 to Interfere with Actin Cytoskeleton, and Promotes Nematode Parasitism and Pathogenicity

“…Western blot analysis was performed with 1:5000 diluted primary antibodies (anti-Flag and anti-GFP; Proteintech, Chicago, IL, USA) and 1:5000 diluted goat anti-mouse IgG and HRP conjugate (Proteintech) as described previously [ 75 ]. The proteins were visualized using DAB Enhanced substrate kit (Solarbio, Beijing, China).…”

The function of plant PR1 and other members of the CAP protein superfamily in plant–pathogen interactions

“…Similarly, the VAL/VAP protein RsVAP, from the important migratory root endoparasitic nematode Radopholus similis , is highly induced in juveniles and its silencing decreases pathogenicity on tomato. On the other hand, overexpression of RsVAP in tobacco leaves inhibits a PTI response triggered by a bacterial flagellin‐derived peptide (flg22) and prevents a cell death response, suggesting that RsVAP represses the plant's basal immunity (Li et al, 2021 ).…”

Comparative genomics among cyst nematodes reveals distinct evolutionary histories among effector families and an irregular distribution of effector‐associated promoter motifs

“…A number of VAP variants were shown to be implicated in the suppression of both PAMP-and effector-triggered immunity (e.g., Li et al, 2021) for the burrowing nematode Radopholus similis. Our effector family selection also included families that (so far) appear to be specific to the cyst nematode lineages.…”