Transcriptome analysis shows that Glomus versiforme decrease the accumulation and toxicity of cadmium in Ipomoea aquatic Forsk.

So far, the physiological and molecular mechanisms of the impact of arbuscular mycorrhizal fungus (AMF) on Cd absorption, transport and detoxification in Ipomoea aquatica (water spinach) are still unclear. In the present study, a pot experiment was performed to investigate the impact of AMF-Glomus versiforme (Gv) on the photosynthetic characteristics, Cd uptake, antioxidative system and transcriptome in water spinach in the soils supplemented with 5 mg Cd kg-1. Gv inoculation improved significantly the photosynthetic characteristics and growth of water spinach. Furthermore, Gv colonization significantly promoted the activities of catalase (CAT), peroxidase (POD) and glutathione reductase (GR), contents of glutathione (GSH) and ascorbic acid (AsA), and the total antioxidant capacity (TCA), but decreased malondialdehyde (MDA) content in water spinach. In addition, Gv inoculation significantly increased pH in rhizosphere soils and decreased the Cd concentrations and uptakes in water spinach. Importantly, 2670 differentially expressed genes (DEGs) were screened in water spinach root colonized with Gv in 5 mg Cd kg-1 soil, of which 2008 DEGs were upregulated and 662 DEGs were downregulated. Especially, the expression levels of POD, CAT, GR, dehydroascorbate reductase 2 (DHAR2), glutathione S-transferase U8 (GSTU8) and glutathione synthetase (GSHS) and cytochrome P450 (Cyt P450) genes were significantly up-regulated in water spinach inoculated with Gv. Meanwhile, the plant cadmium resistance protein 2 (PCR2), metal tolerance protein 4 (MTP4), ATP-binding cassette transporter C family member (ABCC), ABC-yeast cadmium factor 1 (ABC-YCF1) and metallothionein (MT) genes were also up-regulated in mycorrhizal water spinach. Our results firstly elucidated the mechanism by which AMF reduced the uptake and phytotoxicity of Cd in water spinach through a transcriptome analysis.

Glomus versiforme and intercropping with Sphagneticola calendulacea decrease Cd accumulation in maize.

Little information is available on the influence of the compound use of intercropping (IN) and arbuscular mycorrhizal fungus (AMF) on Cd accumulation and the expression of Cd transporter genes in two intercropped plants. A pot experiment was conducted to study the influences of IN and AMF-Glomus versiforme on growth and Cd uptake of two intercropped plants-maize and Cd hyperaccumulator Sphagneticola calendulacea, and the expression of Cd transporter genes in maize in Cd-polluted soils. IN, AMF and combined treatments of IN and AMF (IN + AMF) obviously improved biomass, photosynthesis and total antioxidant capacities of two plants. Moreover, single and compound treatments of IN and AMF evidently reduced Cd contents in maize, and the greatest decreases appeared in the compound treatment. However, Cd contents of S. calendulacea in IN, AMF and IN + AMF groups were notably improved. Furthermore, the single and compound treatments of IN and AMF significantly downregulated the expression levels of Nramp1, HMA1, ABCC1 and ABCC10 in roots and leaves, and the largest decreases were observed in the combined treatment. Our work first revealed that the combined use of IN and AMF appeared to have a synergistic effect on decreasing Cd content by downregulating the expression of Cd transporter genes in maize.

The intercropping and arbuscular mycorrhizal fungus decrease Cd accumulation in upland rice and improve phytoremediation of Cd-contaminated soil by Sphagneticola calendulacea (L.) Pruski.

Little is known about the impact of the combined application of intercropping and arbuscular mycorrhizal fungus (AMF) on the plant growth and Cd accumulation in the two intercropped plants. A greenhouse pot experiment was performed to investigate the effects of intercropping (IC) and AMF-Glomus versiforme (GV) on the growth, photosynthesis, Cd accumulation and antioxidant activities in the two intercropped plants-upland rice and Cd hyperaccumulator Sphagneticola calendulacea (L.) Pruski in the soils added with 5 mg Cd kg-1. It was found that the GV inoculation and the combined treatment of IC and GV (IC + GV) significantly (p < 0.05) increased the biomasses and the P contents of upland rice and S. calendulacea. In addition, the Cd concentrations and uptakes of plants in IC, GV and IC + GV treatments were significantly (p < 0.05) dropped in upland rice but increased in S. calendulacea compared with the monocropping control, and the compound treatment showed better effect on decreasing Cd accumulation in upland rice (especially grains) and increasing Cd uptake by S. calendulacea compared with the single intercropping or AMF treatment. Moreover, IC, GV and IC + GV treatments significantly (p < 0.05) improved the net photosynthetic rate, stomatal conductance and transpiration rate of the two intercropped plants. Finally, IC, GV and IC + GV treatments all significantly increased the catalase activities and total antioxidant capacities, while decreased the malondialdehyde contents in upland rice and S. calendulacea. The present work could provide a feasible strategy for safe production of upland rice and phytoremediation of Cd contaminated soils.

The effect of Funneliformis mosseae on the plant growth, Cd translocation and accumulation in the new Cd-hyperaccumulator Sphagneticola calendulacea.

The screening and identification of hyperaccumulators is the key to the phytoremediation of soils contaminated by heavy metal (HM). Arbuscular mycorrhizal fungus (AMF) can improve plant growth and tolerance to HM; therefore, AMF-assisted phytoextraction has been regarded as a potential technique for the remediation of HM-polluted soils. A greenhouse pot experiment was conducted to determine whether Sphagneticola calendulacea is a Cd-hyperaccumulator and to investigate the effect of the AMF-Funneliformis mosseae (FM) on plant growth and on the accumulation, subcellular distribution and chemical form of Cd in S. calendulacea grown in soils supplemented with different Cd levels. At 25, 50 and 100 mg Cd kg-1 level, S. calendulacea showed high Cd tolerance, the translocation factor and the bioconcentration factor exceeded 1, and accumulation of more than 100 mg Cd kg-1 was observed in the aboveground parts of the plant, meeting the requirements for a Cd-hyperaccumulator. Moreover, FM colonization significantly increased both biomasses and Cd concentration in S. calendulacea. After FM inoculation, the Cd concentrations and proportions increased in the cell walls, but exhibited no significant change in the organelles of the shoots. Meanwhile, FM symbiosis contributed to the conversion of Cd from highly toxic chemical forms (extracted by 80% ethanol and deionized water) to less toxic chemical forms (extracted by 1 M NaCl, 2% acetic acid, 0.6 M HCl) of Cd in the shoots. Overall, S. calendulacea is a typical Cd-hyperaccumulator, and FM symbiosis relieved the phytotoxicity of Cd and promoted plant growth and Cd accumulation, and thus greatly increasing the efficiency of phytoextraction for Cd-polluted soil. Our study provides a theoretical basis and application guidance for the remediation of Cd-contaminated soil by the symbiont of S. calendulacea with FM.

The effect of arbuscular mycorrhizal fungi and biochar on the growth and Cd/Pb accumulation in Zea mays.

A greenhouse pot experiment was conducted to assess the effects of biochar (BC) and arbuscular mycorrhizal fungus (AMF)-Funneliformis mosseae (Fm), Glomus versiforme (Gv) and Rhizophagus intraradices (Ri) on the plant growth and Cd/Pb accumulation by corn grown in the soils artificially contaminated with 5 mg Cd and 300 mg Pb kg-1 soil. The single AMF inoculation and combined usage of AMF and BC evidently improved the P contents of maize. Furthermore, the combined use of AMF and BC produced pronounced positive effect on corn growth, and the shoot biomass in Gv + BC group was 9.85-fold higher than that of the control. Meanwhile, the single BC addition and combined utilization of AMF and BC significantly reduced Cd and Pb concentrations in maize, and the greater reduces were found in the combined utilization, and the lowest Cd concentration of shoot was appeared in Gv + BC group. The single BC addition and combined application of AMF and BC significantly increased soil pH, and reduced soil diethylenetriaminepentaacetic acid (DTPA)-extractable Cd/Pb. This study demonstrated a synergistic effect between AMF (Gv, Fm, Ri) and BC on improving maize growth and decreasing Cd/Pb accumulation in maize, and the combined use of Gv and BC brought the most pronounced effect, which could provide a feasible strategy for safe production of maize from Cd/Pb-polluted soils.

Combined application of arbuscular mycorrhizal fungi and steel slag improves plant growth and reduces Cd, Pb accumulation in Zea mays.

Little attention has been paid to the combined use of arbuscular mycorrhizal fungus (AMF) and steel slag (SS) for ameliorating heavy metal polluted soils. A greenhouse pot experiment was conducted to study the effects of SS and AMF-Funneliformis mosseae (Fm), Glomus versiforme (Gv) and Rhizophagus intraradices (Ri) on plant growth and Cd, Pb uptake by maize grown in soils added with 5 mg Cd kg-1 and 300 mg Pb kg-1 soil. The combined usage of AMF and SS (AMF + SS) promoted maize growth, and Gv + SS had the most obvious effect. Meanwhile, single SS addition and AMF + SS decreased Cd, Pb concentrations in maize, and the greater reductions were found in combined utilization, and the lowest Cd, Pb concentrations of maize appeared in Gv + SS. Single SS amendment and AMF + SS enhanced soil pH and decreased soil diethylenetriaminepentaacetic acid (DTPA)-extractable Cd, Pb concentrations. Furthermore, alone and combined usage of AMF and SS increased contents of soil total glomalin. Our research indicated a synergistic effect between AMF and SS on enhancing plant growth and reducing Cd, Pb accumulation in maize, and Gv + SS exerted the most pronounced effect. This work suggests that AMF inoculation in combination with SS addition may be a potential method for not only phytostabilization of Pb-Cd-contaminated soil but maize safety production.

Arbuscular mycorrhizal fungi alleviate Cd phytotoxicity by altering Cd subcellular distribution and chemical forms in Zea mays.

Arbuscular mycorrhizal fungus (AMF) can relieve Cd phytotoxicity and improve plant growth, but the mechanisms involved in this process have still been not completely known. In the present work, a pot experiment was conducted to examine productions of glutathione (GSH) and phytochelatins (PCs), and absorption, chemical forms and subcellular distribution of Cd in maize (Zea mays) inoculated with or without AMF (Rhizophagus intraradices (Ri) and Glomus versiforme (Gv)) in Cd-amended soils (0, 1 and 5 mg Cd kg-1 soil). In general, both Ri and Gv inoculation dramatically enhanced biomass production and reduced Cd concentrations in shoots and roots of maize when compared to the non-mycorrhizal treatment. Moreover, both Ri and Gv symbiosis obviously increased contents of GSH and PCs, both in shoots and roots. Subcellular distribution of Cd in maize indicated that most of Cd (more than 90%) was accumulated in cell wall and soluble fraction. In addition, Cd proportions in soluble fractions in shoots of maize inoculated with Gv or Ri were considerably increased, but reduced in cell wall fractions compared to non-mycorrhizal maize, indicating that mycorrhizal symbiosis promoted Cd transfer to vacuoles. Furthermore, proportions of Cd in inorganic and water-soluble forms were declined, but elevated in pectates and proteins-integrated forms in mycorrhizal maize, which suggested that Gv and Ri could convert Cd into inactive forms. These observations could provide a further understanding of potential Cd detoxification mechanism in maize inoculated with AMF.

Can arbuscular mycorrhizal fungi reduce Cd uptake and alleviate Cd toxicity of Lonicera japonica grown in Cd-added soils?

A greenhouse pot experiment was conducted to study the impact of arbuscular mycorrhizal fungi--Glomus versiforme (Gv) and Rhizophagus intraradices (Ri) on the growth, Cd uptake, antioxidant indices [glutathione reductase (GR), ascorbate peroxidase (APX), superoxide dismutase (SOD), catalase (CAT), ascorbate (ASA), glutathione (GSH) and malonaldehyde (MDA)] and phytochelatins (PCs) production of Lonicera japonica in Cd-amended soils. Gv and Ri significantly increased P acquisition, biomass of shoots and roots at all Cd treatments. Gv significantly decreased Cd concentrations in shoots and roots, and Ri also obviously reduced Cd concentrations in shoots but increased Cd concentrations in roots. Meanwhile, activities of CAT, APX and GR, and contents of ASA and PCs were remarkably higher in Gv/Ri-inoculated plants than those of uninoculated plants, but lower MDA and GSH contents in Gv/Ri-inoculated plants were found. In conclusion, Gv and Ri symbiosis alleviated Cd toxicity of L. japonica through the decline of shoot Cd concentrations and the improvement of P nutrition, PCs content and activities of GR, CAT, APX in inoculated plants, and then improved plant growth. The decrease of shoot Cd concentrations in L. japonica inoculated with Gv/Ri would provide a clue for safe production of this plant from Cd-contaminated soils.

Effect of Inoculation with Glomus versiforme on Cadmium Accumulation, Antioxidant Activities and Phytochelatins of Solanum photeinocarpum.

The plant growth, phosphate acquisition, Cd translocation, phytochelatins (PCs) production and antioxidant parameters [superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (POD), ascorbate peroxidase (APX), glutathione reductase (GR), glutathione (GSH), ascorbate (ASA) and malonaldehyde (MDA)] were investigated in Cd-hyperaccumulator Solanum photeinocarpum inoculated with Glomus versiforme BGC GD01C (Gv) in Cd-added soils (0, 5, 10, 20, 40 mg Cd kg-1 soil). Mycorrhizal colonization rates were generally high (from 77% to 94%), and hardly affected by Cd. Gv colonization significantly enhanced P acquisition, growth and total Cd uptakes in both shoots and roots of S. photeinocarpum at all Cd levels. Meanwhile, Gv symbiosis significantly increased Cd concentration in the roots, and decreased Cd concentration in the shoots at all Cd levels, which indicates that Gv could promote phytostabilization by enhancing Cd accumulation in the roots to inhibit its translocation to shoots and the "dilution effects" linked to an increase in plant dry matter yield and a reduced Cd partitioning to shoots. Moreover, the improvement of CAT, POD and APX activities in the leaves of mycorrhizal plants infers that Gv symbiosis helped S. photeinocarpum to relieve oxidative damage to biomolecules in Cd-contaminated soil. The evident decline of MDA content in the leaves of mycorrhizal plants indicates that Gv symbiosis evidently improved antioxidant activities, and the enhancement of PCs production in the leaves of mycorrhizal plants suggests that Gv-inoculated plant may be more efficient to relieve Cd phytotoxicity. Therefore, the possible mechanisms of Cd phytotoxicity alleviation by Gv can be concluded as the decline of Cd concentration in the shoots and the improvement of P acquisition, PCs production and activities of CAT, POD, APX in mycorrhizal plants.

Characterization of bacteria in the rhizosphere soils of Polygonum pubescens and their potential in promoting growth and Cd, Pb, Zn uptake by Brassica napus.

Microbe-enhanced phytoremediation has been considered as a promising measure for the remediation of metal-contaminated soils. In this study, two bacterial strains JYX7 and JYX10 were isolated from rhizosphere soils of Polygonum pubescens grown in metal-polluted soil and identified as of Enterobacter sp. and Klebsiella sp. based on 16S rDNA sequences, respectively. JYX7 and JYX10 showed high Cd, Pb and Zn tolerance and increased water-soluble Cd, Pb and Zn concentrations in culture solution and metal-added soils. Two isolates produced plant growth-promoting substances such as indole acetic acid, siderophore, 1-aminocyclopropane-1-carboxylic deaminase, and solubilized inorganic phosphate. Based upon their ability in metal tolerance and solubilization, two isolates were further studied for their effects on growth and accumulation of Cd, Pb, and Zn in Brassica napus (rape) by pot experiments. Rapes inoculated with JYX7 and JYX10 had significantly higher dry weights, concentrations and uptakes of Cd, Pb, Zn in both above-ground and root tissues than those without inoculation grown in soils amended with Cd (25 mg kg(-1)), Pb (200 mg kg(-1)) or Zn (200 mg kg(-1)). The present results demonstrated that JYX7 and JYX10 are valuable microorganism, which can improve the efficiency of phytoremediation in soils polluted by Cd, Pb, and Zn.