摘要
The majority of terrestrial vascular plants are capable of forming mutualistic associations with obligate biotrophic arbuscular mycorrhizal （AM） fungi from the phylum Glomeromycota. This mutualistic symbiosis provides carbohydrates to the fungus, and reciprocally improves plant phosphate uptake. AM fungal trans- porters can acquire phosphate from the soil through the hyphal networks. Nevertheless, the precise func- tions of AM fungal phosphate transporters, and whether they act as sensors or as nutrient transporters, in fungal signal transduction remain unclear. Here, we report a high-affinity phosphate transporter GigmPT from Gigaspora margarita that is required for AM symbiosis. Host-induced gene silencing of GigmPT ham- pers the development of G. margarita during AM symbiosis. Most importantly, GigmPT functions as a phos- phate transceptor in G. margarita regarding the activation of the phosphate signaling pathway as well as the protein kinase A signaling cascade. Using the substituted-cysteine accessibility method, we identified residues A146 （in transmembrane domain [TNID] IV） and Va1357 （in TMD VIII） of GigmPT, both of which are critical for phosphate signaling and transport in yeast during growth induction. Collectively, our results pro- vide significant insights into the molecular functions of a phosphate transceptor from the AM fungus G. margarita.
The majority of terrestrial vascular plants are capable of forming mutualistic associations with obligate biotrophic arbuscular mycorrhizal （AM） fungi from the phylum Glomeromycota. This mutualistic symbiosis provides carbohydrates to the fungus, and reciprocally improves plant phosphate uptake. AM fungal trans- porters can acquire phosphate from the soil through the hyphal networks. Nevertheless, the precise func- tions of AM fungal phosphate transporters, and whether they act as sensors or as nutrient transporters, in fungal signal transduction remain unclear. Here, we report a high-affinity phosphate transporter GigmPT from Gigaspora margarita that is required for AM symbiosis. Host-induced gene silencing of GigmPT ham- pers the development of G. margarita during AM symbiosis. Most importantly, GigmPT functions as a phos- phate transceptor in G. margarita regarding the activation of the phosphate signaling pathway as well as the protein kinase A signaling cascade. Using the substituted-cysteine accessibility method, we identified residues A146 （in transmembrane domain [TNID] IV） and Va1357 （in TMD VIII） of GigmPT, both of which are critical for phosphate signaling and transport in yeast during growth induction. Collectively, our results pro- vide significant insights into the molecular functions of a phosphate transceptor from the AM fungus G. margarita.
