A switch in Ca2+ spiking signature is concomitant with endosymbiotic microbe entry into cortical root cells of Medicago truncatula

During the initial stages of root colonization by either nitrogen-fixing rhizobia or arbuscular mycorrhizal (AM) fungi, the microsymbionts traverse outer root tissues within specialized intracellular compartments of plant origin, thus avoiding direct contact with the host cytoplasm and the activation of defence responses. In order to study the mechanisms underlying this unique form of transcellular infection we have developed in vivo experimental approaches based on confocal microscopy for the model legume Medicago truncatula with the objective of monitoring host cellular dynamics and associated intracellular signaling.