Perception of the novel MAMP eMax from different Xanthomonas species requires the Arabidopsis receptor-like protein ReMAX and the receptor kinase SOBIR

As part of their innate immune system plants carry a number of pattern recognition receptors (PRR s) that can detect a broad range of microbe-associated molecular patterns (MAM Ps). In a recently published article(1) we described a novel, proteinaceous MAM P termed eMax (enigmatic MAM P of Xanthomonas) that derives from Xanthomonas and gets recognized by the receptor-like protein ReMA X (RECEPTOR OF eMax) of Arabidopsis thaliana. ReMA X has no ortholog in Nicotiana benthamiana and this species does not respond to eMax even when transformed with ReMA X. However, interfamily transfer of eMax perception was successful with a chimeric form of ReMA X where the C-terminal part of the protein was replaced by the corresponding part of the tomato RLP EIX2 (ETH YLENE IN DUCIN G XYLANA SE2). In this addendum we describe the difficulties with the purification and identification of the MAM P eMax and we present data demonstrating that functionality of ReMA X, much like that of related RLPs, depends on the presence of the receptor kinase SOBIR (SUPPRESSOR OF BIR 1-1).