Convergent evolution of plant pattern recognition receptors sensing cysteine-rich patterns from three microbial kingdoms

Plants deploy pattern recognition receptors to detect microbe- and damage-associated molecular patterns. Arabidopsis thaliana receptor-like protein RLP30 contributes to innate immunity to the necrotrophic fungus Sclerotinia sclerotiorum by recognizing SCLEROTINIA CULTURE FILTRATE ELICITOR 1 (SCFE1). Here we show that the S. sclerotiorum small cysteine-rich protein SCP1 accounts for elicitor activity of SCFE1. RLP30 recognizes SCP1 and its homologs from divergent fungi and oomycetes, as well as an SCP1-unrelated and conserved pattern from bacterial Pseudomonads. Stable expression of RLP30 in Nicotiana tabacum confers enhanced immunity to bacterial, fungal, and oomycete pathogens. Unlike Arabidopsis, which requires intact SCP1 for RLP30-mediated immunity, other Brassicaceae and Solanaceae respond to smaller immunogenic SCP1 epitopes. We conclude that Arabidopsis RLP30 recognizes immunogenic patterns from three microbial kingdoms and that mechanistically different SCP1 perception has evolved in other plant species, likely as a result of convergent evolution.