9. Nodulation

We have long been interested in the topics of signal transduction and molecular exchanges between Rhizobium and host cells during nodule development in legume plants. We have discovered different genes that play key roles in the perception of the Rhizobium-derived Nodulation factor (Nod factor) signal by the host cells of the model plant Lotus japonicus. Among many interesting new discoveries is the characterization of the nad1 (Nodules with Activated Defense 1) mutant that does not allow Rhizobium cells to multiply and survive inside the developing nodules (Wang et al., 2016). This mutant is of special interest and importance to us, because the gene (NAD1) is found to serve as a master regulator in turning off the cell defense systems in order to allow the ‘invading’ Rhizobium cells to survive and propagate inside the infection threads during normal Rhizobium infection. The discovery of NAD1, an ER-membrane protein, as a master regulator of plant defense system has added another key piece to the Jigsaw puzzle in our understanding of the regulation of plant defense systems that are capable of distinguishing a ‘friendly symbiont’ from ‘deadly pathogens’