P-421 - Mediation of NF-Induced Root Hair Deformation and Rhizobial Infection by the RALF-FER-AHA module

In the legume-rhizobia symbiotic nitrogen fixation process, compatible rhizobia attach to host root hairs, initiating root hair deformation and curling. This eventually leads to the formation of a tunnel-like structure in the root hairs known as an infection thread (IT), through which bacteria into nodule primordia. Rhizobial secreted nodulation factor (NF) is known to induce root hair deformation (RHD), with only the NF receptors, and not other NF signaling transduction components, being involved in this process. Here we have discovered that RAPID ALKALIZATION FACTOR （RALF）and plasma membrane H+-ATPase（AHA）are both induced by NFs. Mutation of these genes or the RALF receptor FERNONIA（FER） resulted in reduced root hair deformation and fewer infection events. Furthermore, the expression AHA in ralf mutant could restore infection defect, indicating that RALF-FER-AHA operate within the same signaling pathway. Through RNA-seq analysis，we observed a reduction in the expression of numerous cell wall-related genes in ralf and aha mutant. These findings underscore the regulatory role of RALF-FER-AHA in NF-induced RHD and rhizobial infection in Lotus japonicus.