LAUSR

The mechanisms underlying the ability of plants to differentiate between pathogens and commensals in their environment are currently unresolved. It has been suggested that spatio-temporal regulation of pattern recognition receptor (PRR) content may be one of the components providing the plant with the ability to distinguish between pathogens and non-pathogenic microbes. The LeEIX PRRs recognize xylanases derived from beneficial or commensal plant colonizers of Trichoderma species, including the xylanase known as EIX. Here, we investigated possible general roles for PRRs from the LeEIX locus in immunity and pathogen resistance in tomato. Mutating the inhibitory PRR LeEIX1, or overexpressing the activating PRR LeEIX2, resulted in resistance to a wide range of pathogens, and increased basal and elicited immunity. LeEIX1 knockout caused increases in the expression level of several tested PRRs including FLS2, as well as bacterial pathogen resistance coupled with an increase in flg22-mediated immunity. The wild tomato relative S. pennellii contains inactive LeEIX PRR variants. S. pennellii does not respond to elicitation with the LeEIX PRRs ligand, EIX. Given that EIX is derived from a mostly non-pathogenic microbe, the connection of its PRRs to disease resistance has not previously been directly investigated. Here, we observed that compared to S. lycopersicum cv M82, S. pennellii was more sensitive to several fungal and bacterial pathogens. Our results suggest that the LeEIX locus may determine resistance to fungal necrotrophs, while the resistance to biotrophs is effected in combination with a gene / QTL not within the LeEIX locus.