Abstract

Bacterial pathogens and most nitrogen-fixing rhizobia employ type III effectors (T3Es) as potent tools to manipulate plant signaling pathways, thereby facilitating infection and colonization. However, how rhizobial T3Es regulate legume symbiosis remains elusive. Here, we show that NopM, a T3E from Sinorhizobium fredii NGR234, contributes to infection and nodulation in Lotus japonicus Gifu. The loss of nopM in an NGR234 ΔnopT mutant reduced infection and nodulation in L. japonicus , and expression of NopM under the control of L. japonicus NIN promoter enhanced these processes. NopM associated with the NF receptors NFR1 and NFR5 and physically interacted with their cytosolic domains in vitro , and selectively mediated ubiquitination of NFR5. Expression of NopM in hairy roots of NFR5 -HA transgenic plants correlated with increased NFR5 protein abundance relative to the inactive NopM variant. Taken together, our work suggests that NopM-dependent effects on symbiosis are associated with increased NFR5 abundance, expanding our understanding of rhizobial T3E functionality and the co-evolution of legume-rhizobium symbiosis.