Atypical Receptor Kinase RINRK1 Required for Rhizobial Infection But Not Nodule Development in .

During the legume-rhizobium symbiotic interaction, rhizobial invasion of legumes is primarily mediated by a plant-made tubular invagination called an infection thread (IT). Here, we identify a gene in encoding a Leu-rich repeat receptor-like kinase (LRR-RLK), (), that is induced by Nod factors (NFs) and is involved in IT formation but not nodule organogenesis. A paralog, RINRK2, plays a relatively minor role in infection. is required for full induction of early infection genes, including Nodule Inception (), encoding an essential nodulation transcription factor. displayed an infection-specific expression pattern, and NIN bound to the promoter, inducing its expression. was found to be an atypical kinase localized to the plasma membrane and did not require kinase activity for rhizobial infection. We propose RINRK1 is an infection-specific RLK, which may specifically coordinate output from NF signaling or perceive an unknown signal required for rhizobial infection.