The soybean mycorrhiza-inducible phosphate transporter gene, GmPT7, also shows localized expression at the tips of vein endings of senescent leaves

Co-inoculation of Soybean Seedling with Trichoderma asperellum and Irpex laceratus Promotes the Absorption of Nitrogen and Phosphorus

Soybean are one of the main oil crops in the world. The study demonstrated that co-inoculation with Trichoderma asperellum (Sordariomycetes, Hypocreomycetidae) and Irpex laceratus (Basidiomycota, Polyporales) isolated from Kosteletzkya virginica can promote the growth of soybean seedlings. The two fungi were found to produce various enzymes, including cellulase, amylase, laccase, protease, and urease. Upon inoculation, T. asperellum mainly colonized within the phloem of the roots in soybean seedlings, while I. laceratus mainly in the xylem and phloem of the roots. Physiological parameters, such as plant height, root length, and fresh weight, were significantly increased in soybean seedlings co-inoculated with T. asperellum and I. laceratus. Moreover, the expression of key genes related to N and P absorption and metabolism was also increased, leading to improved N and P utilization efficiency in soybean seedlings. These results indicate that the two fungi may have complementary roles in promoting plant growth, co-inoculation with T. asperellum and I. laceratus can enhance the growth and nutrient uptake of soybean. These findings suggest that T. asperellum and I. laceratus have the potential to be used as bio-fertilizers to improve soybean growth and yield.

Cooperative interactions between nitrogen fixation and phosphorus nutrition in legumes

Legumes such as soybean are considered important crops as they provide proteins and oils for humans and livestock around the world. Different from other crops, leguminous crops accumulate nitrogen (N) for plant growth through symbiotic nitrogen fixation (SNF) in coordination with rhizobia. A number of studies have shown that efficient SNF requires the cooperation of other nutrients, especially phosphorus (P), a nutrient deficient in most soils. During the last decades, great progress has been made in understanding the molecular mechanisms underlying the interactions between SNF and P nutrition, specifically through the identification of transporters involved in P transport to nodules and bacteroids, signal transduction, and regulation of P homeostasis in nodules. These studies revealed a distinct N-P interaction in leguminous crops, which is characterized by specific signaling cross talk between P and SNF. This review aimed to present an updated picture of the cross talk between N fixation and P nutrition in legumes, focusing on soybean as a model crop, and Medicago truncatula and Lotus japonicus as model plants. We also discuss the possibilities for enhancing SNF through improving P nutrition, which are important for high and sustainable production of leguminous crops.

Multi-omics analysis of the regulatory effects of low-phosphorus stress on phosphorus transport in soybean roots

The regulatory effects of uneven phosphorus supplies on phosphorus transport in soybean roots are still unclear. To further analyze the regulatory effects of low-phosphorus stress on phosphorus transport in soybean roots and the effects of uneven phosphorus application on the physiological mechanism of phosphorus transport in soybean roots, dual-root soybean plants were prepared via grafting, and a sand culture experiment was performed. From the unfolded cotyledon stage to the initial flowering stage, one side of each dual-root soybean system was irrigated with a low-phosphorus-concentration solution (phosphorus-application [P+] side), and the other side was irrigated with a phosphorus-free nutrient solution (phosphorus-free [P-] side); this setup allowed the study of the effects of different phosphorus supply levels on the expression of genes and proteins and the accumulation of metabolites in soybean roots on the P- side to clarify the method through which phosphorus transport is regulated in soybean roots and to provide a theoretical basis for improving the use rate of phosphorus fertilizer. The results revealed that the unilateral supply of low-concentration phosphorus promoted the uptake of phosphorus by soybean roots and the transport of phosphorus from the P+ side to the P- side. Compared with the normal concentration of phosphorus supply and the phosphorus-free supply, the low concentration phosphorus supply affected the regulation of the metabolic pathways involved in starch and sucrose metabolism, glycolysis, fructose, and mannose metabolism, etc., thereby affecting soybean root phosphorus transport. The low-phosphorus stress inhibited fructose synthesis and sucrose synthase synthesis in the soybean roots and the synthesis of hexokinase (HK) and fructose kinase, which catalyzes the conversion of fructose to fructose-6-phosphate. Low-phosphorus stress promoted the synthesis of sucrose invertase and the conversion of sucrose into maltose by the activity of starch synthase (StS) and stimulated the synthesis of UDPG pyrophosphorylase (UGP) and phosphoglucose isomerase (GP1), which is involved in the conversion of UDP-glucose to glucose-6-phosphate. The phosphorus transport pathway of soybean roots was then affected, which promoted phosphorus allocation to UTP and glucose-6-phosphate. Additionally, low-phosphorus stress hastened glycolysis in the soybean roots and inhibited the synthesis of malic acid, thereby promoting the transport of phosphorus in the roots. In addition, low-phosphorus stress inhibited the synthesis of fructose, mannose, and mannose-1-phosphate and the synthesis of other enzymes involved in phosphorus transport as well as invertase, thereby inhibiting the transport and synthesis of several organic phosphorus-containing compounds.

Nitrate Uptake and Use Efficiency: Pros and Cons of Chloride Interference in the Vegetable Crops

Over the past five decades, nitrogen (N) fertilization has been an essential tool for boosting crop productivity in agricultural systems. To avoid N pollution while preserving the crop yields and profit margins for farmers, the scientific community is searching for eco-sustainable strategies aimed at increasing plants' nitrogen use efficiency (NUE). The present article provides a refined definition of the NUE based on the two important physiological factors (N-uptake and N-utilization efficiency). The diverse molecular and physiological mechanisms underlying the processes of N assimilation, translocation, transport, accumulation, and reallocation are revisited and critically discussed. The review concludes by examining the N uptake and NUE in tandem with chloride stress and eustress, the latter being a new approach toward enhancing productivity and functional quality of the horticultural crops, particularly facilitated by soilless cultivation.

Isolation and Characterization of Endomycorrhizal Fungi Associated with Growth Promotion of Blueberry Plants

Despite their notable root mutualism with blueberries (Vaccinium spp.), studies related to Ericoid mycorrhizal (ERM) are relatively limited. In this study, we report the isolation of 14 endomycorrhizal fungi and their identification by fungal colony morphology characterization combined with PCR-amplified fungal internal transcribed spacer (ITS) sequence analyses. Six of the isolated strains were confirmed as beneficial mycorrhizal fungi for blueberry plants following inoculation. We observed the formation of typical ERM hyphae coil structures—which promote and nutritionally support growth—in blueberry seedlings and significant nitrogen and phosphorous content increases in diverse tissues. QRT-PCRs confirmed changes in VcPHT1s expression patterns. After the formation of ERM, PHT1-1 transcription in roots was upregulated by 1.4- to threefold, whilst expression of PHT1-3 and PHT1-4 in roots were downregulated 72% and 60%, respectively. Amino acid sequence analysis of all four VcPHT1s genes from the blueberry variety “Sharpblue” revealed an overall structural similarity of 67% and predicted transmembrane domains. Cloning and overexpression of PHT1-1 and PHT1-3 genes in transgenic Arabidopsis thaliana plants significantly enriched total phosphorus and chlorophyll content, confirming that PHT1-1 and PHT1-3 gene functions are associated with the transport and absorption of phosphorus.

Genome-Wide Identification and Expression Profile Analysis of the PHT1 Gene Family in Gossypium hirsutum and Its Two Close Relatives of Subgenome Donor Species

Phosphate transporter (PHT) is responsible for plant phosphorus (P) absorption and transport. PHT1 is a component of the high-affinity phosphate transporter system and plays pivotal roles in P absorption under P starvation conditions. However, in cotton, the number and identity of PHT1 genes that are crucial for P absorption from soil remain unclear. Here, genome-wide identification detected twelve PHT1 genes in Gossypium hirsutum and seven and eight PHT1 genes in two close relatives of the G. hirsutum genome-G. arboreum and G. raimondii, respectively. In addition, under low-phosphate treatment, the expressions of GaPHT1;3, GaPHT1;4, and GaPHT1;5 in roots were upregulated after 3 h of induction, and GhPHT1;3-At, GhPHT1;4-At, GhPHT1;5-At, GhPHT1;3-Dt, GhPHT1;4-Dt, and GhPHT1;5-Dt in the roots began to respond after 1 h of induction. Homologous pairs-GaPHT1;4 and GhPHT1;4-At; GaPHT1;5 and GhPHT1;5-At; GrPHT1;4 and GhPHT1;4-Dt, with GhPHT1;5-Dt and GhPHT1;5-At being syntenic-were all highly expressed in the roots under normal conditions. Among the genes highly expressed in the roots, GhPHT1;4-At, GhPHT1;5-At, GhPHT1;4-Dt and GhPHT1;5-Dt were continuously upregulated by P starvation. Therefore, it is concluded that these four genes might be key genes for P uptake in cotton roots. The results of this study provide insights into the mechanisms of P absorption and transport in cotton.

Mechanisms and Impact of Symbiotic Phosphate Acquisition

Phosphorous is important for life but often limiting for plants. The symbiotic pathway of phosphate uptake via arbuscular mycorrhizal fungi (AMF) is evolutionarily ancient and today occurs in natural and agricultural ecosystems alike. Plants capable of this symbiosis can obtain up to all of the phosphate from symbiotic fungi, and this offers potential means to develop crops less dependent on unsustainable P fertilizers. Here, we review the mechanisms and insights gleaned from the fine-tuned signal exchanges that orchestrate the intimate mutualistic symbiosis between plants and AMF. As the currency of trade, nutrients have signaling functions beyond being the nutritional goal of mutualism. We propose that such signaling roles and metabolic reprogramming may represent commitments for a mutualistic symbiosis that act across the stages of symbiosis development.

Lateral Transport of Organic and Inorganic Solutes

Organic (e.g., sugars and amino acids) and inorganic (e.g., K⁺, Na⁺, PO₄2-, and SO₄2-) solutes are transported long-distance throughout plants. Lateral movement of these compounds between the xylem and the phloem, and vice versa, has also been reported in several plant species since the 1930s, and is believed to be important in the overall resource allocation. Studies of Arabidopsis thaliana have provided us with a better knowledge of the anatomical framework in which the lateral transport takes place, and have highlighted the role of specialized vascular and perivascular cells as an interface for solute exchanges. Important breakthroughs have also been made, mainly in Arabidopsis, in identifying some of the proteins involved in the cell-to-cell translocation of solutes, most notably a range of plasma membrane transporters that act in different cell types. Finally, in the future, state-of-art imaging techniques should help to better characterize the lateral transport of these compounds on a cellular level. This review brings the lateral transport of sugars and inorganic solutes back into focus and highlights its importance in terms of our overall understanding of plant resource allocation.

Expression of four phosphate transporter genes from Finger millet (Eleusine coracana L.) in response to mycorrhizal colonization and Pi stress

Phosphorus (P) is a vital nutrient for plant growth and development, and is absorbed in cells with the help of membrane-spanning inorganic phosphate transporter (Pht) protein. Symbiosis with arbuscular mycorrhiza (AM) also helps in transporting P from the soil to plant and Pht proteins play an important role in it. To understand this phenomenon in Finger Mille plant, we have cloned four Pht genes from Finger millet, which shares the homology with Pht1 protein family of cereals. Expression pattern analysis during the AM infection indicated that EcPT4 gene was AM specific, and its expression was higher in roots where AM colonization percentage was high. The expression level of EcPT1-4 gene under the phosphorous (Pi) stress in seedlings was found to be consistent with its role in acquisition of phosphorus. Homology study of the EcPt proteins with Pht proteins of cereals shows close relationship. The findings of the study indicate that Pht1 family genes from finger millet can serve to be an important resource for the better understanding of phosphorus use efficiency.

Phosphate Uptake and Allocation - A Closer Look at Arabidopsis thaliana L. and Oryza sativa L

This year marks the 20th anniversary of the discovery and characterization of the two Arabidopsis PHT1 genes encoding the phosphate transporter in Arabidopsis thaliana. So far, multiple inorganic phosphate (Pi) transporters have been described, and the molecular basis of Pi acquisition by plants has been well-characterized. These genes are involved in Pi acquisition, allocation, and/or signal transduction. This review summarizes how Pi is taken up by the roots and further distributed within two plants: A. thaliana and Oryza sativa L. by plasma membrane phosphate transporters PHT1 and PHO1 as well as by intracellular transporters: PHO1, PHT2, PHT3, PHT4, PHT5 (VPT1), SPX-MFS and phosphate translocators family. We also describe the role of the PHT1 transporters in mycorrhizal roots of rice as an adaptive strategy to cope with limited phosphate availability in soil.