A new mechanism of vacuolar phosphorus transporter regulating root nodule symbiosis and phosphorus adaptation in legumes discovered in Northwest Agriculture and Forestry

Recently, the research group of Associate Professor Liu Jinlong from the School of Grassland Technology published a research paper entitled “VPT-like genes modulate Rhizobium-legume symbiosis and phosphorus adaptation” online on “The Plant Journal”. Yang Rongchen, Yan Jun, and Li Chun, master graduates of the School of Grass Industry, are the co-first authors, and Associate Professor Liu Jinlong is the corresponding author.

Vacuole phosphate transporters (VPTs) are essential for phosphorus adaptation in plants, but their roles in rhizobia-legume symbiosis are poorly understood. Here, we systematically investigated the functions of VPT1 homologues (MtVPTs) in Medicago truncatula in rhizobia-legume symbiosis and phosphorus adaptation. The results showed that MtVPT2 and MtVPT3 mainly responded positively to low and high phosphorus, respectively. However, both mtvpt2 and mtvpt3 mutants exhibit high phosphate-sensitivity and low-phosphate-tolerant stalk types. mtvpt3 significantly increased root-to-shoot phosphate transfer efficiency, while mtvpt2 significantly decreased root-to-shoot phosphate transfer efficiency, and decreased and increased root cytoplasmic phosphorus concentrations, respectively. Low phosphorus stress could induce the expression of MtVPT2 and MtVPT3 in root nodules (Fig. 1a). Mutations of MtVPT2 and MtVPT3 significantly reduced nodule number and nitrogenase activity under different phosphorus conditions (Fig. 1b). The cytoplasmic P concentration of mtvpt2 and mtvpt3 mutants was significantly lower than that of wild type, especially in tissues near the nodule base, which may be due to the long-distance transport of P and insufficient supply of cytosolic P (Fig. 1c). Under low P stress, mtvpt2 and mtvpt3 cannot maintain stable cytosolic P levels in the nodule nitrogen fixation zone like wild type. These results suggest that MtVPT2 and MtVPT3 may regulate phosphorus adaptation and the symbiotic process between rhizobia and legumes by regulating long-distance phosphorus transport, which may provide new ideas for genetic improvement of efficient phosphorus uptake and utilization in alfalfa and other legumes .

The research was funded by the National Natural Science Foundation of China, the China Postdoctoral Science Foundation, and the school’s experimental technology research and laboratory management innovation project.

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