Identification of an arbuscular mycorrhiza-specific phosphate transporter gene and characterization of its RNAi knockdown transformants

Abstract

Arbuscular mycorrhizal (AM) fungi are ancient symbionts on plant roots. AM fungi uptake phosphate (Pi) through extraradical mycelium that extends beyond rhizosphere and supplies Pi to plants. In return, plants supply photosynthates to AM fungi. An AM-specific Pi transporter gene of Lotus japonicus, a model legume, was identified and its knockdown transformants were prepared. Under Pi-limiting conditions, the transformants showed reduction of Pi uptake via AM roots. The transformants also exhibited reduced numbers of fungal arbuscules and vesicles, and an increased nuumber of plant root cells showing hypersensitive response-like symptom. Thus, sufficient Pi uptake through the AM-specific phosphate transporter is necessary for establishment of normal symbiosis including development of fungal structures and suppression of plant defense response.