Insights into Symbiotic Plant-Fungal Communication using Innovative Imaging Approaches
R. ROTH (1), S. Hillmer (2), K. Schumacher (3), J. Skepper (4), U. Paszkowski (5) (1) University of Cambridge, United Kingdom; (2) EMCF@COS, Germany; (3) COS, Germany; (4) CAIC, England; (5) University of Cambridge, England

To accommodate arbuscular mycorrhiza fungi (AMF) most land plants initiate monumental cellular reprogramming within the inner root cortex culminating in the development of complex tree-shaped feeding structures called arbuscules. Surrounding the arbuscule is a host-derived membrane called the peri-arbuscular membrane (PAM) that facilitates nutrient exchange and potentiates communication between plant and fungus. The extent to which host and symbiont membranes are tailored for dialogue and our understanding of how membrane proteins are delivered and retained within the PAM remain unclear. The aim of this work was to pioneer innovative imaging approaches for rice roots colonized by Rhizophagus irregularis to 1.) Investigate to what extend structural adaptations of membranes shape the plant-fungal interface and 2.) Monitor functionally distinct PAM-specific protein dynamics during arbuscule development. Using high-pressure freezing, transmission electron microscopy and 3-D tomography we uncover novel membrane structures produced at the symbiotic interface. This points to extensive structural adaptation and unconventional secretion to facilitate communication between host and fungus. Analyses of membrane proteins associated with symbiosis using deep-tissue whole mount multi-photon confocal microscopy shows that Phosphate Transporter 11 (PT11) protein is secreted transiently and to distinct PAM foci adjacent to growing hyphal tips. We postulate that these PAM foci represent areas of heightened fungal phosphate delivery and uptake via PT11 into the plant cortical cell. Our data provide novel insights into the spatio-temporal regulation of functionally diverse membrane proteins during arbuscule development and point to highly regulated functional foci at the PAM that facilitate plant-fungal communication during symbiosis.

Abstract Number: C13-3, P2-61
Session Type: Concurrent