Sequence adaptations in the intracellular domain of Symbiosis receptor-like kinase (SymRK) promoted infection thread progression in root nodule primordia

The uptake of nitrogen-fixing bacteria into living plant cells and the intracellular accommodation of arbuscular mycorrhiza (AM) fungi requires the plasma membrane-localised Symbiosis Receptor-like Kinase (SymRK). AM is widespread across terrestrial vascular plant lineages, while the nitrogen-fixing root nodule symbiosis (RNS) is restricted to one clade within the eurosids. This distribution led to the concept that SymRK was adopted during evolution to mediate RNS. Comparative analyses revealed that SymRK orthologs from the eurosid clade support RNS while SymRK from the phylogenetically distant species Solanum lycopersicum (tomato) does not. To dissect the molecular basis for this different