Nature 553, 342–346 (2018)

Each plant cell contains hundreds of plasma membrane receptors that are constantly on the lookout for environmentally produced or endogenous signals. Members of the largest receptor subfamily display extracellular leucine-rich repeats (LRRs) as their sensing antenna and an intracellular kinase domain as their signalling switch, creating molecular bridges between the outside and inside of the cell. We know a few examples of these receptor kinases binding to each other through the LRR domain, forming active heterodimer complexes. Youssef Belkhadir and colleagues have now mapped the full interaction network.

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The authors tested all pairwise interactions for 200 Arabidopsis LRR extracellular domains to build an almost complete map. They validated the robustness and biological relevance of these interactions through various approaches, including genetics. New receptors acting in immunity and growth were discovered, and receptors with small LRR domains were found to be quite promiscuous. Genetically removing one of these central nodes indirectly disrupted biological responses controlled by other receptors, showing that the network’s overall stability is important.

We used to think of membrane receptors as isolated entities, at most interacting with one co-receptor, each starting an isolated downstream signalling pathway. This work not only identifies new candidates to explore individually, but exposes a much more complex view of an interconnected grid of receptors influencing each other to correctly integrate and process extracellular information.