Regulation of signal transduction and bacterial infection during root nodule symbiosis

Among plant–microbe interactions, root nodule symbiosis is one of the most important beneficial interactions providing legume plants with nitrogenous compounds. Over the past years a number of genes required for root nodule symbiosis has been identified but most recently great advances have been made to dissect signalling pathways and molecular interactions triggered by a set of receptor-like kinases. Genetic and biochemical approaches have not only provided evidence for the cross talk between bacterial infection of the host plant and organogenesis of a root nodule but also gained insights into dynamic regulation processes underlying successful infection events. Here, we summarise recent progress in the understanding of molecular mechanisms that regulate and trigger cellular signalling cascades during this mutualistic interaction.

Research highlights
► LysM receptors are required for perception of bacterial and fungal LCOs.
► Intracellular bacterial infection occurs in the absence of Nod Factor receptors.
► Symbiotic receptors are regulated by ubiquitinating enzymes.
► Activation of CCaMK is the core of early signalling events.
► Molecular scaffolds and membrane rafts are required for symbiosis.