Identification and characterization of a novel PAMP from a widespread microbial virulence factor and its perception system in Arabidopsis

Abstract

NEP1-like proteins (NLPs) are phytotoxins and microbial virulence factors secreted by bacteria, oomycetes and fungi capable of exerting immune responses in dicot plant species. Previously, this immunogenic activity has been linked to cytotoxicity, supposedly through toxin-mediated release of endogenous signals of danger called DAMPs (damage-associated molecular patterns). Here, immunogenic activity could be traced back to a 20 amino acid stretch within a Phytophthora parasitica-derived NLP, designated as nlp20. Immunogenic orthologous sequences can be found in NLPs of bacteria, oomycetes and fungi; a unique distribution pattern of all known PAMPs to date. Nlp20 is perceived by the Arabidopsis LRR-RP (leucine-rich repeat receptor protein) RLP23, likely forming a tripartite receptor complex with the LRR-RK-type (leucine-rich repeat receptor kinase) co-receptors SERK3/BAK1 (somatic embryogenesis receptor 3/BRI1-associated kinase 1) and SOBIR1/EVR (suppressor of BIR1-1/evershed) to facilitate downstream signaling. SOBIR1/EVR interacts constitutively and independent of nlp20 with RLP23, whereas SERK3/BAK1 gets recruited into the receptor complex in a nlp20-dependent fashion only. Interfamily transfer of RLP23 into the crop potato confers disease resistance against devastating pathogens such as Phytophthora infestans and Sclerotinia sclerotiorum, turning RLP23 into a promising candidate for future engineering of durable broad-spectrum disease resistance in important crops.