Functional Characterization of Acer Truncatum PHT1 Family Phosphate Transporter Genes and Their Involvement in Arbuscular Mycorrhizal Symbiosis

Acer truncatum Bunge, an economically significant species, is often growth-limited by phosphorus availability. Phosphate transporters, especially the PHT1 family, are crucial for plant phosphorus absorption, transport, and redistribution. This study aimed to elucidate the role of Acer truncatum PHT1 genes in phosphorus transport. We cloned five PHT1 family genes (AtPT1, AtPT2, AtPT4, AtPT9, and AtPT11) and investigated their expression and function under varying phosphorus regimes in the context of arbuscular mycorrhizal (AM) symbiosis with Rhizophagus irregularis. Real-time quantitative PCR revealed differential gene expression patterns in response to AM colonization and phosphorus levels. Functional characterization through yeast complementation, tobacco overexpression, subcellular localization, and GUS reporter gene assays confirmed the plasma membrane localization and typical PHT1 family traits of these transporters. AM colonization upregulated AtPT4 and AtPT11, with AtPT11 having a specific induction pattern for mycorrhizal phosphorus acquisition. AtPT4 was linked to phosphorus uptake via mycorrhizal symbiosis, AtPT1 is involved in phosphorus remobilization within plant tissues, AtPT2 in phosphorus transport and remobilization (suppressed by AM colonization), and AtPT9 in phosphorus uptake and transport efficiency under high-phosphorus conditions. These findings provide insights into the molecular mechanisms underlying phosphorus homeostasis in Acer truncatum and its mycorrhizal interactions.