Fig. 5.

Proposed model depicting putative LCO-receptor kinases on the plasma membrane and the cross-talks between different symbiotic signaling pathways in Medicago. NF are perceived with high stringency by NF receptor (NFP) and its putative heteromultimeric partner, an NFR1 homolog. This accounts for majority of signal transduction events. However, NF-induced, but NFP-independent signaling responses suggest the existence of other receptor complexes. Differential transcriptional regulation of these candidate genes by both NF and GSE in NFP-independent manner suggests the existence of Myc factor receptor, which is capable of perceiving NF. Interestingly, NFP-independent, but NF-specific transcriptional responses suggest the existence of NF-specific “cryptic” signaling receptor in Medicago. Although a majority of these transcriptional responses are dependent on DMI3, GSE-induced DMI3-independent transcriptional regulation of candidate genes, suggest the existence of parallel signaling pathway, which is independent of well established signaling pathway comprising DMI genes.