Selenium alleviates chromium stress and promotes chromium uptake in As-hyperaccumulator Pteris vittata: Cr reduction and cellar distribution.

Arsenic-hyperaccumulator Pteris vittata exhibits remarkable absorption ability for chromium (Cr) while beneficial element selenium (Se) helps to reduce Cr-induced stress in plants. However, the effects of Se on the Cr uptake and the associated mechanisms in P. vittata are unclear, which were investigated in this study. P. vittata plants were grown for 14 days in 0.2-strength Hoagland solution containing 10 (Cr10) or 100 µM (Cr100) chromate (CrVI) and 1 µM selenate (Se1). The plant biomass, malondialdehyde contents, total Cr and Se contents, Cr speciation, expression of genes associated with Cr uptake, and Cr subcellular distribution in P. vittata were determined. P. vittata effectively accumulated Cr by concentrating 96-99% in the roots under Cr100 treatment. Further, Se substantially increased its Cr contents by 98% to 11,596 mg kg-1 in the roots, which may result from Se's role in reducing its oxidative stress as supported by 27-62% reduction in the malondialdehyde contents. Though supplied with CrVI, up to 98% of the Cr in the roots was reduced to insoluble chromite (CrIII), with 83-89% being distributed on root cell walls. Neither Cr nor Se upregulated the expression of sulfate transporters PvSultr1;1-1;2 or phosphate transporter PvPht1;4, indicating their limited role in Cr uptake. P. vittata effectively accumulates Cr in the roots mainly as CrIII on cell walls and Se effectively enhances its Cr uptake by reducing its oxidative stress. Our study suggests that Se can be used to enhance P. vittata Cr uptake and reduce its oxidative stress, which may have application in phytostabilization of Cr-contaminated soils.

Foliar-selenium enhances plant growth and arsenic accumulation in As-hyperaccumulator Pteris vittata: Critical roles of GSH-GSSG cycle and arsenite antiporters PvACR3.

It is known that selenium (Se) enhances plant growth and arsenic (As) accumulation in As-hyperaccumulator Pteris vittata, but the associated mechanisms are unclear. In this study, P. vittata was exposed to 50 µM arsenate (AsV) under hydroponics plus 25 or 50 µM foliar selenate. After 3-weeks of growth, the plant biomass, As and Se contents, As speciation, malondialdehyde (MDA) and glutathione (GSH and GSSG) levels, and important genes related to As-metabolism in P. vittata were determined. Foliar-Se increased plant biomass by 17 - 30 %, possibly due to 9.1 - 19 % reduction in MDA content compared to the As control. Further, foliar-Se enhanced the As contents by 1.9-3.5 folds and increased arsenite (AsIII) contents by 64 - 136 % in the fronds. The increased AsV reduction to AsIII was attributed to 60 - 131 % increase in glutathione peroxidase activity, which mediates GSH oxidation to GSSG (8.8 -29 % increase) in the fronds. Further, foliar-Se increased the expression of AsIII antiporters PvACR3;1-3;3 by 1.6 - 2.1 folds but had no impact on phosphate transporters PvPht1 or arsenate reductases PvHAC1/2. Our results indicate that foliar-Se effectively enhances plant growth and arsenic accumulation by promoting the GSH-GSSG cycle and upregulating gene expression of AsIII antiporters, which are responsible for AsIII translocation from the roots to fronds and AsIII sequestration into the fronds. The data indicate that foliar-Se can effectively improve phytoremediation efficiency of P. vittata in As-contaminated soils.

Effects of temperature on plant growth and arsenic removal efficiency of Pteris vittata in purifying arsenic-contaminated water in winter: A two-year year-round field study.

Phytoremediation is a cost-effective and eco-friendly alternative method for arsenic (As) contaminated water treatment. This study conducted a two-year year-round field study (cycle1 and cycle2) in a temperate area (Sendai, Japan) using small As-hyperaccumulator Pteris vittata seedlings to reduce pre-cultivation time and associated costs. The number of seedlings was changed from 256 in the cycle1 period to 165 in the cycle2 period to evaluate the As removal efficiency of P. vittata for As-contaminated water in field conditions with different plant densities. Before the winter season, with continuously increasing fronds, rhizomes, and roots growth, this reduction did not affect the plant's As removal efficiency for As-contaminated water to decrease the As concentration from 30 µg/L to the environmental quality standard for As in water, set at 10 µg/L in Japan. During the winter season, we found that cold weather caused P. vittata to wither and release the accumulated As into water without a greenhouse (cycle1). In the meantime, the bioaccumulation factor (BAF) and the translocation factor (TF) values for fronds of P. vittata decreased (BAF for fronds: from 66,089 to 8,460; TF for fronds: from 13.4 to 3.4). On the other hand, with greenhouse protection (cycle2), P. vittata did not severely wither and kept accumulating As. Moreover, BAF and TF values for fronds of P. vittata increased (BAF for fronds: from 24,372 to 36,740; TF for fronds: from 5.2 to 17.2). Maintaining the air temperature inside the greenhouse, particularly around the rhizomes, above 0 °C may be the reason why P. vittata remained alive and functional during the cold winter. These results indicate that a single-layer polyethylene greenhouse was sufficient for the tropical-subtropical As-hyperaccumulator fern P. vittata to survive the cold winter and snow in the temperate area, enabling year-round phytoremediation treatment of As-contaminated water in the open field.

Potential in treating arsenic-contaminated water of the biochars produced from hyperaccumulator Pteris vittata and its environmental safety.

In this study, biochar derived from pyrolyzed aboveground parts of Pteris vittata (P. vittata) was modified with iron(Fe) and applied to aqueous solutions containing arsenite (As[III]) or arsenate (As[V]) for remediation purposes. The adsorption efficiency, biochar characteristics pre- and post-adsorption, microscopic As distribution, and As morphology were analyzed. Additionally, the potential and leaching safety of P. vittata biochar for As-contaminated water remediation were evaluated. Results indicated that P. vittata biochar contained oxygen-containing functional groups and aromatic structures. Modification with Fe increased specific surface area and total pore volume. Unmodified P. vittata biochar displayed low adsorption of As(III) and As(V), while Fe modification significantly enhanced As adsorption capacity and reduced As leaching by 69%-89%. Maximum adsorption capacities of Fe-modified P. vittata biochar for As(III) and As(V) were 7.64 and 10.2 mg/g, respectively, as determined by Langmuir fitting. The superior adsorption efficiency of As(V) over As(III) by Fe-modified biochar was attributed to better electrostatic interaction with the adsorbent. Analysis revealed similar As species in P. vittata biochar before and after adsorption, with a significant presence of As(III). Remarkably, As in P. vittata remained highly stable during pyrolysis and adsorption, possibly due to strong Fe-As binding. Fe-modified P. vittata biochar shows promise for application, but further pretreatment may be necessary to achieve optimal results.

Novel phosphatase PvPAP1 from the As-hyperaccumulator Pteris vittata promotes organic P utilization and plant growth: Extracellular exudation and phytate hydrolysis.

Organic phosphorus (Po) is a large component of soil P, but it is often unavailable for plant uptake. Purple acid phosphatases (PAP) can hydrolyze a wide range of Po, playing an important role in Po utilization by plants. In this study, we investigated a novel secretary PvPAP1 from the As-hyperaccumulator Pteris vittata, which can effectively utilize exogenous Po, including adenosine triphosphate (ATP) and phytate. Unlike other PAP, PvPAP1 was abundantly-expressed in P. vittata roots, which was upregulated 3.5-folds under P-deprivation than P-sufficient conditions. When expressed in tobacco, its activity in the roots of PvPAP1-Ex lines was ∼8 folds greater than that in wild-type (WT) plants. Besides, PvPAP1 exhibited its secretory ability as evidenced by the sapphire-blue color on the root surface after treating with 5-bromo-4-chloro-3-indolyl phosphate. In a long-term experiment using sand media, PvPAP1-expressing tobacco plants showed 25-30 % greater root biomass than WT plants when using ATP as the sole P source. This is because PvPAP1-expression enhanced its phosphatase activity by 6.5-9.2 folds in transgenic tobacco, thereby increasing the P contents by 39-41 % in its roots under ATP treatment and 9.4-30 % under phytate treatment. The results highlight PvPAP1 as a novel secreted phosphatase crucial for external Po utilization in P. vittata, suggesting that PvPAP1 has the potential to serve as a valuable gene resource for enhancing Po utilization by crop plants.

Influence of Pteris vittata-maize intercropping on plant agronomic parameters and soil arsenic remediation.

To achieve "production while remediation" in arsenic (As) -contaminated farmlands, a field experiment was conducted to investigate the effects of five Pteris vittata L. (PV) - maize intercropping modes on the growth, nutrient, and As accumulation characteristics of PV and maize. The intercropping increased the As content of PV by 2.9%-132.0% and decreased the As content in maize shoots by 15.5%-37.0%. Total As accumulation in above-ground plant parts reached 202.03-941.97 g hm-2. Intercropping also improved nitrogen and phosphorus content in maize kernels by 27.6%-124.7% and 15.9%-31.5%, respectively. Additionally, intercropping increased maize kernel 100-grain weight by 10.0%-16.6% and resulted in a 1.1%-24.1% increase in maize yield compared to sole cultivation. The intercropping transformed soil As from iron-bound to calcium-bound and aluminum-bound forms. Analysis of soil microbial diversity showed that the intercropping decreases the abundance of Chloroflexi and increases the abundance of Proteobacteria. Among the five modes, the intercropping mode with 4 rows of maize and 4 rows of PV showed the highest remediation efficiency and mechanized operation. These findings contribute to a theoretical framework and technical support for the simultaneous soil pollution remediation and productive farming practices.

Three new pterosins from Pteris semipinnata.

Three new pterosins, named as semipterosin A (1), B (2) and C (3), together with 11 known pterosins (4-14), were isolated from the aerial parts of Pteris semipinnata. Their structures were elucidated by HRESI-MS, NMR spectral data, CD and literature comparisons. Three new pterosins were assessed for their anti-inflammatory activity. Compounds 1-3 inhibited the NF-kB induction by 40.7%, 61.9% and 34.0%, respectively. This is the first report of the isolation of compounds 6-14 from this plant.

Bacteria associated with Comamonadaceae are key arsenite oxidizer associated with Pteris vittata root.

Pteris vittata (P. vittata), an arsenic (As) hyperaccumulator commonly used in the phytoremediation of As-contaminated soils, contains root-associated bacteria (RAB) including those that colonize the root rhizosphere and endosphere, which can adapt to As contamination and improve plant health. As(III)-oxidizing RAB can convert the more toxic arsenite (As(III)) to less toxic arsenate (As(V)) under As-rich conditions, which may promote plant survial. Previous studies have shown that microbial As(III) oxidation occurs in the rhizospheres and endospheres of P. vittata. However, knowledge of RAB of P. vittata responsible for As(III) oxidation remained limited. In this study, members of the Comamonadaceae family were identified as putative As(III) oxidizers, and the core microbiome associated with P. vittata roots using DNA-stable isotope probing (SIP), amplicon sequencing and metagenomic analysis. Metagenomic binning revealed that metagenome assembled genomes (MAGs) associated with Comamonadaceae contained several functional genes related to carbon fixation, arsenic resistance, plant growth promotion and bacterial colonization. As(III) oxidation and plant growth promotion may be key features of RAB in promoting P. vittata growth. These results extend the current knowledge of the diversity of As(III)-oxidizing RAB and provide new insights into improving the efficiency of arsenic phytoremediation.

Novel Phosphate Transporter-B PvPTB1;1/1;2 Contribute to Efficient Phosphate Uptake and Arsenic Accumulation in As-Hyperaccumulator Pteris vittata.

Arsenic (As) contamination in soil poses a potential threat to human health via crop uptake. As-hyperaccumulator Pteris vittata serves as a model plant to study As uptake and associated mechanisms. This study focuses on a novel P/AsV transport system mediated by low-affinity phosphate transporter-B 1 family (PTB1) in P. vittata. Here, we identified two plasma-membrane-localized PTB1 genes, PvPTB1;1/1;2, in vascular plants for the first time, which were 4.4-40-fold greater in expression in P. vittata than in other Pteris ferns. Functional complementation of a yeast P-uptake mutant and enhanced P accumulation in transgenic Arabidopsis thaliana confirmed their role in P uptake. Moreover, the expression of PvPTB1;1/1;2 facilitated the transport and accumulation of As in both yeast and A. thaliana shoots, demonstrating a comparable AsV uptake capacity. Microdissection-qPCR analysis and single-cell transcriptome analysis collectively suggest that PvPTB1;1/1;2 are specifically expressed in the epidermal cells of P. vittata roots. PTB1 may play a pivotal role in efficient P recycling during phytate secretion and hydrolysis in P. vittata roots. In summary, the dual P transport mechanisms consisting of high-affinity Pht1 and low-affinity PTB1 may have contributed to the efficient P/As uptake in P. vittata, thereby contributing to efficient phytoremediation for As-contaminated soils.

Arsenic-Hyperaccumulator Pteris vittata Effectively Uses Sparingly-Soluble Phosphate Rock: Rhizosphere Solubilization, Nutrient Improvement, and Arsenic Accumulation.

Sparingly-soluble phosphate rock (PR), a raw material for P-fertilizer production, can be effectively utilized by the As-hyperaccumulator Pteris vittata but not most plants. In this study, we investigated the associated mechanisms by measuring dissolved organic carbon (DOC) and acid phosphatase in the rhizosphere, and nutrient uptake and gene expression related to the As metabolism in P. vittata. The plants were grown in a soil containing 200 mg kg-1 As and/or 1.5% PR for 30 days. Compared to the As treatment, the P. vittata biomass was increased by 33% to 4.6 g plant-1 in the As+PR treatment, corresponding to 27% decrease in its frond oxidative stress as measured by malondialdehyde. Due to PR-enhanced DOC production in the rhizosphere, the Ca, P, and As contents in P. vittata fronds were increased by 17% to 9.7 g kg-1, 29% to 5.0 g kg-1, and 57% to 1045 mg kg-1 in the As+PR treatment, thereby supporting its better growth. Besides, PR-induced rhizosphere pH increase from 5.0 to 6.9 promoted greater P uptake by P. vittata probably via upregulating low-affinity P transporters PvPTB1;1/1;2 by 3.7-4.1 folds. Consequently, 29% lower available-P induced the 3.3-fold upregulation of high-affinity P transporter PvPht1;3 in the As+PR treatment, which was probably responsible for the 58% decrease in available-As content in the rhizosphere. Consistent with the enhanced As translocation and sequestration, arsenite antiporters PvACR3/3;3 were upregulated by 1.8-4.4 folds in the As+PR than As treatment. In short, sparingly-soluble PR enhanced the Ca, P, and As availability in P. vittata rhizosphere and improved their uptake via upregulating genes related to As metabolism, suggesting its potential application for improving phytoremediation in As-contaminated soils.

Niche and phenotypic differentiation in fern hybrid speciation, a case study of Pteris fauriei (Pteridaceae).

BACKGROUND AND AIMS: Niche differentiation is a crucial issue in speciation. Although it has a well-known role in adaptive processes of hybrid angiosperms, it is less understood in hybrid ferns. Here, we investigate whether an intermediate ecological niche of a fern hybrid is a novel adaptation that provides insights into fern hybrid speciation. METHODS: Pteris fauriei (Pteridaceae) is a natural hybrid fern, occurring in environments between its parent species. The maternal Pteris minor is found in sunny areas, but the habitat of the paternal Pteris latipinna is shady. We combined data from morphology, leaf anatomy and photosynthetic traits to explore adaptation and differentiation, along with measuring the environmental features of their niches. We also performed experiments in a common garden to understand ecological plasticity. KEY RESULTS: The hybrid P. fauriei was intermediate between the parent species in stomatal density, leaf anatomical features and photosynthetic characteristics in both natural habitats and a common garden. Interestingly, the maternal P. minor showed significant environmental plasticity and was more similar to the hybrid P. fauriei in the common garden, suggesting that the maternal species experiences stress in its natural habitats but thrives in environments similar to those of the hybrid. CONCLUSIONS: Based on the similar niche preferences of the hybrid and parents, we propose hybrid superiority. Our results indicate that the hybrid P. fauriei exhibits greater fitness and can compete with and occupy the initial niches of the maternal P. minor. Consequently, we suggest that the maternal P. minor has experienced a niche shift, elucidating the pattern of niche differentiation in this hybrid group. These findings offer a potential explanation for the frequent occurrence of hybridization in ferns and provide new insights into fern hybrid speciation, enhancing our understanding of fern diversity.

Arsenic-enhanced plant growth in As-hyperaccumulator Pteris vittata: Metabolomic investigations and molecular mechanisms.

The first-known As-hyperaccumulator Pteris vittata is efficient in As uptake and translocation, which can be used for phytoremediation of As-contaminated soils. However, the underlying mechanisms of As-enhanced plant growth are unknown. We used untargeted metabolomics to investigate the potential metabolites and associated metabolic pathways regulating As-enhanced plant growth in P. vittata. After 60 days of growth in an MS-agar medium containing 15 mg kg-1 As, P. vittata biomass was 33-34 % greater than the no-As control. Similarly, the As contents in P. vittata roots and fronds were 272 and 1300 mg kg-1, considerably greater than the no-As control. Univariate and multivariate analyses based on electrospray ionization indicate that As exposure changed the expression of 1604 and 1248 metabolites in positive and negative modes. By comparing with the no-As control, As exposure significantly changed the expression of 14 metabolites including abscisic acid, d-glucose, raffinose, stachyose, chitobiose, xylitol, gibberellic acids, castasterone, citric acid, riboflavin-5-phosphate, ubiquinone, ubiquinol, UDP-glucose, and GDP-glucose. These metabolites are involved in phytohormone synthesis, energy metabolism, and sugar metabolism and may all potentially contribute to regulating As-enhanced plant growth in P. vittata. Our data provide clues to understanding the metabolic regulations of As-enhanced plant growth in P. vittata, which helps to enhance its phytoremediation efficiency of As-contaminated soils.

Influence of biochar on the arsenic phytoextraction potential of Pteris vittata in soils from an abandoned arsenic mining site.

Biochar (BC) has a strong potential for activating arsenic (As) in soil; thus, the phytoremediation efficiency of As-polluted soils is enhanced with Pteris vittata L. A pot experiment was conducted to investigate the potential of BC to assist in phytoremediation with P. vittata. The effects of BC on physicochemical properties, available As, enzyme activities, and the bacterial community in the rhizosphere soil were investigated, and the biomass, physiology, and As uptake of P. vittata were analyzed. The results indicated that applying BC facilitated available As in the P. vittata rhizosphere soil, and the phytoremediation efficiency percentage increased in the As-polluted soils, such as 3.80% and 8.01% under the 2% and 5% BC treatments compared to the control, respectively. Phytoremediation with P. vittata and BC significantly improved soil organic matter content, available N, P, and K, enzyme activities, and the bacterial community. BC promoted Streptomyces (26.6-54.2%) and Sphingomonas (12.3-30.8%) abundance which regulated the growth and As uptake by P. vittata. Moreover, applying BC increased the biomass, and As uptake by P. vittata. Overall, BC strengthened the phytoremediation of As-polluted soils by improving soil pH, nutrient concentrations, enzyme activities, bacterial community structure, and soil arsenic activation, growth, and absorption by P. vittata.

Insoluble-Phytate Improves Plant Growth and Arsenic Accumulation in As-Hyperaccumulator Pteris vittata: Phytase Activity, Nutrient Uptake, and As-Metabolism.

Phytate, the principal P storage in plant seeds, is also an important organic P in soils, but it is unavailable for plant uptake. However, the As-hyperaccumulator Pteris vittata can effectively utilize soluble Na-phytate, while its ability to utilize insoluble Ca/Fe-phytate is unclear. Here, we investigated phytate uptake and the underlying mechanisms based on the phytase activity, nutrient uptake, and expression of genes involved in As metabolisms. P. vittata plants were cultivated hydroponically in 0.2-strength Hoagland nutrient solution containing 50 µM As and 0.2 mM Na/Ca/Fe-phytate, with 0.2 mM soluble-P as the control. As the sole P source, all three phytates supported P. vittata growth, with its biomass being 3.2-4.1 g plant-1 and Ca/Fe-phytate being 19-29% more effective than Na-phytate. Phytate supplied soluble P to P. vittata probably via phytase hydrolysis, which was supported by 0.4-0.7 nmol P min-1 g-1 root fresh weight day-1 phytase activity in its root exudates, with 29-545 µM phytate-P being released into the growth media. Besides, compared to Na-phytate, Ca/Fe-phytate enhanced the As contents by 102-140% to 657-781 mg kg-1 in P. vittata roots and by 43-86% to 1109-1447 mg kg-1 in the fronds, which was accompanied by 21-108% increase in Ca and Fe uptake. The increased plant As is probably attributed to 1.3-2.6 fold upregulation of P transporters PvPht1;3/4 for root As uptake, and 1.8-4.3 fold upregulation of arsenite antiporters PvACR3/3;1/3;3 for As translocation to and As sequestration into the fronds. This is the first report to show that, besides soluble Na-phytate, P. vittata can also effectively utilize insoluble Ca/Fe-phytate as the sole P source, which sheds light onto improving its application in phytoremediation of As-contaminated sites.

Intercropping of Pteris vittata and maize on multimetal contaminated soil can achieve remediation and safe agricultural production.

Soil contamination by multimetals is widespread. Hyperaccumulator-crop intercropping has been confirmed to be an effective method for arsenic (As)- or cadmium (Cd)-contaminated soil that can achieve soil cleanup and agricultural production. However, the influencing factors and response of hyperaccumulator-crop intercropping to multimetal-contaminated soil are still unclear. In this study, intercropping of the As hyperaccumulator Pteris vittata and maize was conducted on two typical types of multimetal-contaminated soil, namely, Soil A contaminated by As, Cd, and lead (Pb) and Soil B contaminated by As, Cd, and chromium (Cr). Intercropping reduced As, Cd, and Pb in the maize grains by 60 %, 66.7 %, and 20.4 %, respectively. The concentrations of As, Cd, Pb, and Cr in P. vittata increased by 314 %, 300 %, 447.3 %, and 232.6 %, respectively, relative to their concentrations in the monoculture plants. Two soils with different levels of contamination showed that higher heavy metal content might diminish the ability of intercropping to reduce soil heavy metal risk. No notable difference in soil microbial diversity was found between the intercropped and monocultured plants. The composition of microbial communities of intercropping groups were more similar to those of monoculture P. vittata on two different soils (Soils A and B). An imbalance between the amount of As taken up by the plants and the reduction in As in the soil was observed, and this imbalance may be related to watering, As leaching, and heterogeneity of soil As distribution. Reducing the risk resulting from As leaching and enhancing the efficiency of phytoextraction should be emphasized in remediation practices.

Nitrogen addition accelerates litter decomposition and arsenic release of Pteris vittata in arsenic-contaminated soil from mine.

The arsenic (As) release from litter decomposition of As-hyperaccumulator (Pteris vittata L.) in mine areas poses an ecological risk for metal dispersion into the soil. However, the effect of atmospheric nitrogen (N) deposition on the litter decomposition of As-hyperaccumulator in the tailing mine area remains poorly understood. In this study, we conducted a microcosm experiment to investigate the As release during the decomposition of P. vittata litter under four gradients of N addition (0, 5, 10, and 20 mg N g-1). The N10 treatment (10 mg N g-1) enhanced As release from P. vittata litter by 1.2-2.6 folds compared to control. Furthermore, Streptomyces, Pantoea, and Curtobacterium were found to primarily affect the As release during the litter decomposition process. Additionally, N addition decreased the soil pH, subsequently increased the microbial biomass, as well as hydrolase activities (NAG) which regulated N release. Thereby, N addition increased the As release from P. vittata litter and then transferred to the soil. Moreover, this process caused a transformation of non-labile As fractions into labile forms, resulting in an increase of available As concentration by 13.02-20.16% within the soil after a 90-day incubation period. Our findings provide valuable insights into assessing the ecological risk associated with As release from the decomposition of P. vittata litter towards the soil, particularly under elevated atmospheric N deposition.

Arbuscular mycorrhizal fungi promote arsenic accumulation in Pteris vittata L. through arsenic solubilization in rhizosphere soil and arsenic uptake by hyphae.

The introduction of arbuscular mycorrhizal fungi (AMF) is considered an effective strategy for improving the arsenic phytoremediation efficiency of Pteris vittata L. (P. vittata). However, how hyphae take up arsenic and translocate it to the root cells of P. vittata in the symbiotic mycorrhizal structure is currently unclear. In this study, the role of hyphae in arsenic enrichment in P. vittata and the mechanism of arsenic species transformation in the rhizosphere were studied via a compartmented cultivation setup. After Claroidoglomus etunicatum (C. etunicatum) colonization, the arsenic content of P. vittata increased by 234%. Hyphae contributed 32% to the accumulation of arsenic in symbionts. C. etunicatum promoted the conversion of iron and aluminum oxides to crystalline states in rhizosphere soil, promoted the desorption of arsenic bound to iron and aluminum oxides, and increased the content of available arsenic in rhizosphere soil by 116%. The transfer of arsenic from arbuscular structures to root cells was confirmed by transmission electron microscopy (TEM)/scanning electron microscopy- energy dispersive X-ray spectroscopy (SEMEDS) analysis. This study demonstrated that C. etunicatum inoculation enhances the phytoremediation efficiency of P. vittata in arsenic-contaminated soils through hyphal uptake, plant growth promotion, and alteration of the rhizosphere environment.

In Vitro Modulation of Genotoxicity and Oxidative Stress by Polyphenol-Rich Fraction of Chinese Ladder Brake (Pteris vittata L.).

Pteris vittata L. is a terrestrial genus growing in moist, shady forests and on hillsides. The plant has considerable ethnomedicinal importance. Investigations have been carried out on chemical profiling and antioxidant compounds from some genera of pteridophytes but studies on the biological properties of P. vittata are lacking. Therefore, the present study investigates antioxidant, antigenotoxic, and antiproliferative potential of the aqueous fraction of P. vittata (PWE). A battery of assays were carried out to assess the antioxidant potential of the PWE. SOS chromotest and DNA nicking assay were used to evaluate the antigenotoxicity of the fraction. The cytotoxic effect of PWE was analyzed using MTT and Neutral Single Cell Gel Electrophoresis comet assay. EC50 of 90.188 µg/ml, 80.13 µg/ml, 142.836 µg/ml, and 12.274 µg/ml was obtained in DPPH, superoxide anion scavenging, reducing power and lipid peroxidation assays, respectively. PWE was potent in inhibiting Fenton's reagent-induced nicking of pBR322 plasmid. The fraction significantly inhibited hydrogen peroxide (H2O2) and 4-nitroquinoline-N-oxide (4NQO) induced mutagenicity and a reduction in induction factor was found with increased PWE concentration. GI50 of 147.16 µg/ml was obtained in MTT assay in human MCF-7 breast cancer cell line. PWE induced apoptosis as confirmed from confocal microscopy studies. The protective effects can be attributed to the presence of the phytochemicals in PWE. These results will be helpful in the development of functional food characteristics, as well as unravel the benefits of pteridophytes as promoters of health.

Copper enhanced arsenic-accumulation in As-hyperaccumulator Pteris vittata by upregulating its gene expression for As uptake, translocation, and sequestration.

In contaminated soils, arsenic (As) often co-exists with copper (Cu). However, its effects on As accumulation and the related mechanisms in As-hyperaccumulator Pteris vittata remain unclear. In this study, P. vittata plants were exposed to 50 µM As and/or 50 µM Cu under hydroponics to investigate the effects of Cu on plant growth and As accumulation, as well as gene expression related to arsenic uptake (P transporters), reduction (arsenate reductases), and translocation and sequestration (arsenite antiporters). After 14 d of growth and compared to the As treatment, the As concentration in P. vittata fronds increased by 1.4-times from 793 to 1131 mg·kg-1 and its biomass increased by 1.2-fold from 18.0 to 21.1 g·plant-1 in the As+Cu treatment. Copper-enhanced As accumulation was probably due to upregulated gene expressions related to As-metabolisms including As uptake (1.9-fold in P transporter PvPht1;3), translocation (2.1-2.4 fold in arsenite antiporters PvACR3/3;2) and sequestration (1.5-2.0 fold in arsenite antiporters PvACR3;1/3;3). Our results suggest that moderate amount of Cu can help to increase the As accumulation efficiency in P. vittata, which has implication in its application in phytoremedation in As and Cu co-contaminated soils.

Research advances in mechanisms of arsenic hyperaccumulation of Pteris vittata: Perspectives from plant physiology, molecular biology, and phylogeny.

Pteris vittata, as the firstly discovered arsenic (As) hyperaccumulator, has great application value in As-contaminated soil remediation. Currently, the genes involved in As hyperaccumulation in P. vittata have been mined continuously, while they have not been used in practice to enhance phytoremediation efficiency. Aiming to better assist the practice of phytoremediation, this review collects 130 studies to clarify the progress in research into the As hyperaccumulation process in P. vittata from multiple perspectives. Antioxidant defense, rhizosphere activities, vacuolar sequestration, and As efflux are important physiological activities involved in As hyperaccumulation in P. vittata. Among related 19 genes, PHT, TIP, ACR3, ACR2 and HAC family genes play essential roles in arsenate (AsⅤ) transport, arsenite (AsⅢ) transport, vacuole sequestration of AsⅢ, and the reduction of AsⅤ to AsⅢ, respectively. Gene ontology enrichment analysis indicated it is necessary to further explore genes that can bind to related ions, with transport activity, or with function of transmembrane transport. Phylogeny analysis results implied ACR2, HAC and ACR3 family genes with rapid evolutionary rate may be the decisive factors for P. vittata as an As hyperaccumulator. A deeper understanding of the As hyperaccumulation network and key gene components could provide useful tools for further bio-engineered phytoremediation.