Abstract text: Plants integrate information from the cell wall to regulate growth and development, yet the origin and diversification of cell wall associated receptor networks remain unclear. Receptor-like proteins are transmembrane proteins with an extracellular domain and a short cytoplasmic tail functioning in diverse biological processes, including plant development and immunity1. In order to act in signalling, RLPs are required to interact with RLKs. Interestingly, RLPs involved in development, such as RLP44, which interacts with the cell wall and mediates the activation of brassinosteroid (BR) signalling in response to cell wall mediated cues2,3, are well conserved throughout land plants.

Here, we investigate the functional conservation of orthologues of RLP44 in different plant groups, focusing on cell wall feedback signalling in relation to cell wall composition. We found that the orthologue of RLP44 in Marchantia polymorpha, termed MpRLP44 is able to bind to the cell wall similar to Arabidopsis RLP44, a conserved ancestral role of RLP44, predating cell wall integration with BR signalling during plant evolution. Together, we propose a model that RLP44 originally act as a cell wall-associated signalling component providing an evolutionary framework for understanding cell wall-associated signalling modules contributed to the diversification of plant receptor networks.