Figure 1.

Early nodulation gene cascades in legumes. Flavonoids released by the plants are detected by compatible bacteria in the rhizosphere leading to production of Nod factors (NF), which are perceived by a dimer receptor made up of LysM type receptor kinases NFR1 and NFR5 at the root epidermis. This triggers the downstream gene cascade including those involved in nucleoporin, cation channels, calcium spiking, early nodulin expression and cytokinin signalling leading to cortical and pericycle cell divisions, and concomitant bacterial infection.