Transcription factor involved in symbiotic nodule signaling in response to rhizobial Nod factors (NFs) (PubMed:17449807, PubMed:17827349). Binds to the GCC-box (NF-responsive box) of ENOD11 promoter. Acts as transcriptional activator of NF-responsive box-containing target gene promoters in root hairs (PubMed:17827349). Functions as a transcriptional regulator required for root infection by symbiotic rhizobia, infection thread (IT) formation and maintenance, and nodule development. Necessary for NF-induced gene expression and spontaneous nodulation activated by CCAMK. Functions downstream of CCAMK to activate nodulation gene expression (PubMed:17449807). Involved in early stages of root nodule development. Functions redundantly with ERN2. Is essential with ERN2 for the initiation of root hair infection, and nodule organogenesis and development. Required for accurate expression of the NF signaling genes ENOD11 and ENOD12 (PubMed:23077241, PubMed:27208242). Expressed in roots, root hairs and leaves (PubMed:17827349). Expressed in root epidermis and root hairs (PubMed:23077241). Induced in roots from 1 to 21 day after inoculation with Sinorhizobium meliloti (PubMed:17449807). Induced by Nod factors in root hairs (PubMed:17827349). No visible phenotype under normal growth conditions, but roots of mutant plants, are impaired in the interaction with rhizobia, and in infection thread (IT) initiation and maintenance. Belongs to the AP2/ERF transcription factor family. ERF subfamily. Truncated N-terminus.