VPT‐like genes modulate Rhizobium–legume symbiosis and phosphorus adaptation

Abstract

SUMMARYAlthough vacuolar phosphate transporters (VPTs) are essential for plant phosphorus adaptation, their role in Rhizobium–legume symbiosis is unclear. In this study, homologous genes of VPT1 (MtVPTs) were identified in Medicago truncatula to assess their roles in Rhizobium–legume symbiosis and phosphorus adaptation. MtVPT2 and MtVPT3 mainly positively responded to low and high phosphate, respectively. However, both mtvpt2 and mtvpt3 mutants displayed shoot phenotypes with high phosphate sensitivity and low phosphate tolerance. The root‐to‐shoot phosphate transfer efficiency was significantly enhanced in mtvpt3 but weakened in mtvpt2, accompanied by lower and higher root cytosolic inorganic phosphate (Pi) concentration, respectively. Low phosphate induced MtVPT2 and MtVPT3 expressions in nodules. MtVPT2 and MtVPT3 mutations markedly reduced the nodule number and nitrogenase activity under different phosphate conditions. Cytosolic Pi concentration in nodules was significantly lower in mtvpt2 and mtvpt3 than in the wildtype, especially in tissues near the base of nodules, probably due to inhibition of long‐distance Pi transport and cytosolic Pi supply. Also, mtvpt2 and mtvpt3 could not maintain a stable cytosolic Pi level in the nodule fixation zone as the wildtype under low phosphate stress. These findings show that MtVPT2 and MtVPT3 modulate phosphorus adaptation and rhizobia–legume symbiosis, possibly by regulating long‐distance Pi transport.

Nodulation Signaling Pathway 1 and 2 Modulate Vanadium Accumulation and Tolerance of Legumes

“…However, MtVPT3 mutations can also endow plants with V tolerance, but the mechanism of the effect may be different from that of vpt1 . The mutation of MtVPT3 can increase the efficiency of P transport from roots to shoots, [ 24 ] but this also means that it inevitably will increase the absorption and transportation of V. As expected, V concentrations in mtvpt3 shoots were higher than in wild‐type R108 under V stress (Figure S14c , Supporting Information). Unexpectedly, the concentrations of total P and Pi in mtvpt3 shoots were lower than those in R108 (Figure S14d , Supporting Information), which is different from the previously reported results under normal conditions.…”

“…Recently, our research has shown that mutations in MtVPT2 can reduce the efficiency of P transport from roots to shoots. [ 24 ] Arabidopsis thaliana VPT1 is closely related to MtVPT2 , and mutations to it may reduce the efficiency of V transport from roots to shoots. Therefore, vpt1 showed a phenotype of tolerance in shoots and sensitivity in roots under V stress.…”

“…Unexpectedly, the concentrations of total P and Pi in mtvpt3 shoots were lower than those in R108 (Figure S14d , Supporting Information), which is different from the previously reported results under normal conditions. [ 24 ] However, the decrease in Pi concentration means that less Pi is likely to be stored in the vacuole, which favors more P in the cytoplasm to counter V toxicity. Higher P levels in the environment are more conducive to the survival of plants under V stress, which to some extent reflects the role of P in resistance to V toxicity (Figures S4 and S17 , Supporting Information).…”

Influence and Role of Fungi, Bacteria, and Mixed Microbial Populations on Phosphorus Acquisition in Plants

“…Some studies have also found that vacuolar transporters (VPTs), mutants vpt2 and vpt3, significantly reduce the numbers of nodules and nitrogenase activity under different phosphate conditions. VPT2 and VPT3 may regulate phosphorus adaptation and Rhizobium legume symbiosis by regulating long-distance Pi transport [118]. Additionally, in Medicago truncatula, the phosphate transporter gene MtPT6 was found to be expressed in shoots, roots, and nodules, and responded to low-phosphate stress.…”