Flowering plant immune repertoires expand under mycorrhizal symbiosis

Abstract

Immune perception in flowering plants is mediated by a repertoire of cytoplasmic and cell‐surface receptors that detect invading microbes and their effects on cells. Here, we show that several large families of immune receptors exhibit size variations related to a plant's competence to host symbiotic root fungi (mycorrhiza). Plants that do not participate in mycorrhizal associations have significantly smaller immune repertoires, while the most promiscuous symbiotic hosts (ectomycorrhizal plant species) have significantly larger immune repertoires. By contrast, we find no significant increase in immune repertoire size among legumes competent to form a symbiosis with nitrogen‐fixing bacteria (rhizobia). To explain these observations, we hypothesize that plant immune repertoire size expands with symbiote species diversity.

The mysterious non‐arbuscular mycorrhizal status of Brassicaceae species

“…Interestingly, Brassicaceae species including Brassica napus and A. thaliana express lesser NBS‐LRRs, particularly in roots, as compared to other plant species, where root NBS‐LRRs were strongly expressed (Munch et al, 2018). The non‐mycorrhizal status of Brassicaceae seems to be associated with a much smaller plant NBS‐LRR repertoire compared to the mycorrhizal species harbouring a larger family of immune receptors (Kramer et al, 2019).…”