Apoplastic Venom Allergen-like Proteins of Plant Parasitic Nematodes Modulate the Activation of Damage Triggered Immunity by Cell Surface Receptors
Jose Lozano-Torres: Laboratory of Nematology, Wageningen University
<div>Despite causing considerable damage to host tissue, nematodes establish persistent infections in both animals and plants. An elaborate repertoire of nematode effectors modulate damage-triggered immune responses. However, the mode of action of most of nematode immunomodulatory compounds is unknown. We discovered that the nematode effectors venom allergen-like proteins (VAPs) selectively suppress host immunity during the onset of parasitism. VAPs are uniquely conserved in secretions of all animal- and plant-parasitic nematodes, but their role in parasitism has remained elusive. Knocking-down the expression of Gr-VAP1 hampered the infectivity of <em>Globodera rostochiensis</em>. By contrast, heterologous expression of Gr-VAP1 and VAPs from <em>Heterodera schachtii</em> in plants resulted in the loss of basal immunity to multiple pathogens. Surprisingly, VAPs only affect the defense responses mediated by surface-localized immune receptors. The modulation of basal immunity by ectopic VAPs involves extracellular protease-based host defenses and jasmonic acid responses. Crystal structures of VAPs revealed lipid binding motifs which can bind palmitate and sterol both <em>in vitro </em>and <em>in vivo</em>. The delivery of VAPs into host tissue coincides with large modifications in the extracellular matrices by migratory nematodes. We, therefore, conclude that parasitic nematodes most likely utilize VAPs to suppress the activation of defenses by immunogenic breakdown products in damaged host tissue.</div>
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