Abstract

Land plants and beneficial arbuscular mycorrhizal (AM) fungi form life-long associations that depend on the reciprocal trade of essential soil minerals such as inorganic phosphate (Pi) in exchange for host photosynthates. As obligate biotrophs, AM fungi rely on plants for fatty acids, needed to form highly branched intracellular feeding structures called arbuscules and essential to complete their life-cycle. Transient invasion of arbuscules into root cortical cells result in greatly expanded membrane surfaces and provide a large symbiotic interface for symbiotic exchange. Although such synchronized intimacy between host and fungus must be the consequence of a precisely tuned exchange of signals, to date, host-signaling components operating at the plant-derived peri-arbuscular membrane (PAM) surrounding arbuscules have not been reported. Here, I describe a PAM -specific Ser/Thr receptor-like kinase that whilst not required for arbuscule establishment is indispensable for completion of the fungal life-cycle. Our results provide a first indication that the stage post-arbuscule development is critical for maintaining AM symbiosis.