As part of their immune system, plants have pattern recognition receptors (PRRs) that can detect a broad range of microbeassociated molecular patterns (MAMPs). Here, we identified a PRR of Arabidopsis thaliana with specificity for the bacterial MAMP eMax from xanthomonads. Response to eMax seems to be restricted to the Brassicaceae family and also varied among different accessions of Arabidopsis. In crosses between sensitive accessions and the insensitive accession Shakhdara, eMax perception mapped to RECEPTOR-LIKE PROTEIN1 (RLP1). Functional complementation of rlp1 mutants required gene constructs that code for a longer version of RLP1 that we termed ReMAX (for receptor of eMax). ReMAX/RLP1 is a typical RLP with structural similarity to the tomato (Solanum lycopersicum) RLP Eix2, which detects fungal xylanase as a MAMP. Attempts to demonstrate receptor function by interfamily transfer of ReMAX to Nicotiana benthamiana were successful after using hybrid receptors with the C-terminal part of ReMAX replaced by that of Eix2. These results show that ReMAX determines specificity for eMax. They also demonstrate hybrid receptor technology as a promising tool to overcome problems that impede interfamily transfer of PRRs to enhance pathogen detection in crop plants.

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Background With increased environmental concerns and restrictions of chemical control, the importance of other eco-friendly strategies for management of the nematodes is being substantially grown nowadays. One of the most well-known strategies that have attracted the attentions is biological control of these deleterious agents. In our previous study (Moslehi et al. in Egypt J Biol Pest Control 31:1–11, 2021), Bacillus wiedmannii AzBw1 was introduced as a robust antagonistic agent against root-knot nematode Meloidogyne arenaria. Present study addressed the possible mechanisms of action of this strain. Results Based on quantitative bioassays it was shown that the strain AzBw1 is able to produce considerable amount of siderophore, protease, and chitinase. In an in vitro assay conducted by bi-plate Petri dishes, it was shown that hatching of the nematode eggs, subjected to bacterial volatile compounds (BVCs) was 34% lower than those of mock-treated control eggs. On the other hand, mortality of BVC-treated juveniles was 33.5% higher than those of mock-treated control juveniles. The secretory proteins from the medium culture of strain AzBw1 were precipitated and fractionated by anion exchange chromatography (AEC). Fractions from AEC were checked for hydrolytic activity and nematicidal effect. It was found that the fractions with the highest protease activity have a strong nematicidal effect. In contrast, significant nematicidal effect in the fraction with Chitinase activity was detected. Conclusion The results suggested that protease activity played a key role in strain AzBw1 antagonism against root-knot nematode, M. arenaria. Finally, nonvolatile organic compounds were also extracted from the medium culture after removing secretory proteins and enzymes. Obtained results showed that these metabolites had also a strong anti-nematode effect.