LysM-RLK plays an ancestral symbiotic function in plants

Abstract

SummaryTo ensure their water and mineral nutrition, most land plants form arbuscular mycorrhiza (AM) with soil-borne Glomeromycota fungi1. This ∼450 million years old symbiosis was key in driving land colonisation by plants2. In angiosperms, AM is thought to be initiated via the perception by the host plant of AM-fungi derived chito- and lipochito-oligosaccharides leading to the activation of a conserved signalling pathway referred to as the Common Symbiosis Pathway3. Genetics in legumes and monocots have demonstrated that members of the Lysin motif Receptor-Like Kinase (LysM-RLK) family are important for the perception of these AM-fungi derived molecules, although none of the LysM-RLK mutants or combination of mutants described to date fully abolish AM4. This discrepancy with the phenotypes observed for components of the CSP, which fail to host AM fungi, might be the result of genetic redundancy between the multiple LysM-RLK paralogs found in these species. In contrast to angiosperms, the liverwortMarchantia paleaceacontains only four LysM-RLKs. In this study, we demonstrate the essential role of one LysM-RLK for AM inM. paleacea. Furthermore, we present evidence that Marchantia’s ability to respond to chito- or lipochito-oligosaccharides is not a predictor of its symbiotic ability, suggesting the existence of yet uncharacterized AM-fungi signals.HighlightsThe LysM-RLK LYKa is essential for arbuscular mycorrhiza inMarchantia paleaceaThe only LYR fromMarchantia paleaceais not required for arbuscular mycorrhizaLYKa and LYR are both required for chito- and lipochito-oligosaccharide signallingLipochito- and chito-oligosaccharide signalling is not essential for arbuscular mycorrhiza inMarchantia paleacea