Functional Analysis of the Phosphate Transporter Gene MtPT6 From Medicago truncatula

Abstract

Phosphorus is one of the essential macronutrients required by plant growth and development, but phosphate resources are finite and diminishing rapidly because of the huge need in global agriculture. In this study, 11 genes were found in the Phosphate Transporter 1 (PHT1) family of Medicago truncatula. Seven genes of the PHT1 family were available by qRT-PCR. Most of them were expressed in roots, and almost all genes were induced by low-phosphate stress in the nodule. The expression of MtPT6 was relatively high in nodules and induced by low-phosphate stress. The fusion expression of MtPT6 promoter-GUS gene in M. truncatula suggested that the expression of MtPT6 was induced in roots and nodules by phosphate starvation. In roots, MtPT6 was mainly expressed in vascular tissue and tips, and it was also expressed in cortex under low-phosphate stress; in nodules, it was mainly expressed in vascular bundles, cortical cells, and fixation zone cells. MtPT6 had a close relationship with other PHT1 family members according to amino acid alignment and phylogenetic analysis. Subcellular localization analysis in tobacco revealed that MtPT6 protein was localized to the plasma membrane. The heterologous expression of MtPT6 in Arabidopsis knockout mutants of pht1.1 and pht1.4 made seedlings more susceptible to arsenate treatment, and the phosphate concentrations in pht1.1 were higher in high phosphate condition by expressing MtPT6. We conclude that MtPT6 is a typical phosphate transporter gene and can promote phosphate acquisition efficiency of plants.

MtPT5 phosphate transporter is involved in leaf growth and phosphate accumulation of Medicago truncatula

“…It has been reported that there are 11 PHT1 transporters in M. truncatula ( Cao et al, 2020 ). We identified another two members (Mt4g083960 and Mt5g068140) by searching Ensemblplants.…”

“…MtPT4 is highly expressed in mycorrhizal roots, responsible for Pi acquisition from arbuscules ( Harrison et al, 2002 ). It is also expressed in plant root tip in the absence of the arbuscular mycorrhizal (AM) fungus and modulates root branching, whereas it does not significantly affect Pi accumulation in plants without AM symbiosis ( Cao et al, 2020 ). Recently, MtPT6 was reported to be involved in Pi uptake by heterologous expression of MtPT6 in Arabidopsis pht1;1 or pht1;4 mutant.…”

Physiological responses and transcriptomic changes reveal the mechanisms underlying adaptation of Stylosanthes guianensis to phosphorus deficiency

“…8). Numerous PT homologues are found to be enhanced by P deficiency in soybean [23], rice [47] and Medicago (Medicago truncatula) [48]. For example, in Arabidopsis, the transcripts of two Pi transporters (Pht1;1 and Pht1;4) are significantly increased in low P-treated roots, which are involved in Pi uptake [49,50].…”

Nitrogen and Phosphorus Signaling and Transport During Legume–Rhizobium Symbiosis

“…Therefore, different combinations of Pi transporters and Pi stress response factors form diverse regulatory networks in the N fixation and non-fixation zones to maintain Pi homeostasis in response to both systemic and local Pi availability for efficient symbiotic N fixation in soybean nodules ( Lu et al, 2020 ). Eleven members of the PT1 family have been identified in M. truncatula , and most of them were highly expressed under conditions of low Pi ( Cao et al, 2020 ). In addition to root epidermis, cortex, vascular tissues, and root tips, MtPT6 was also expressed in nodules, suggesting that it may play a role in Pi uptake from soil and transporting Pi to nodules from other tissues ( Cao et al, 2020 ).…”

“…Eleven members of the PT1 family have been identified in M. truncatula , and most of them were highly expressed under conditions of low Pi ( Cao et al, 2020 ). In addition to root epidermis, cortex, vascular tissues, and root tips, MtPT6 was also expressed in nodules, suggesting that it may play a role in Pi uptake from soil and transporting Pi to nodules from other tissues ( Cao et al, 2020 ). Pi deficiency induces the expression of purple acid phosphatase (PAPs) in root nodules, which leads to an enhanced acquisition and utilization of P in root nodules ( Li et al, 2017 ; Wang et al, 2020e ).…”