Current Understanding of Cell-Surface Immune Receptors for MAMPs and Plant Parasites in the Solanaceae Family.

Cell-surface receptors play a central role in plant defence by enabling the perception of microbial signatures upon initial contact, activating immune responses and protecting the plant against invasion. In solanaceous plants such as tomato, potato, pepper and their wild relatives, these receptors include pattern-recognition receptors (PRRs) that contribute to recognition of bacteria, fungi and oomycetes. PRR detection of conserved microbe-associated molecular patterns (MAMPs) initiates downstream defence responses that can include the formation of reactive oxygen species, the initiation of MAPK cascades, and the upregulation of defence genes, collectively known as pattern-triggered immunity (PTI). Additional immune receptors at the cell surface detect secreted pathogen virulence proteins and can provide race-specific resistance in the Solanaceae, contributing to a layered defence network that balances broad-spectrum recognition with pathogen-specific immune responses. This review highlights cell-surface immune receptors in the Solanaceae, including PRRs and additional extracellular surveillance proteins that recognize phytopathogens and phytoparasites. We focus on the overall diversity of receptors among solanaceous species, the role of co-receptors in receptor complexes, and downstream signalling networks activated upon MAMP perception. Additionally, we discuss the challenges of inter- and intraspecies receptor compatibility as a limiting step in genetic engineering approaches using solanaceous PRRs for broad-spectrum disease management.