Physiological and molecular responses in phosphorus-hyperaccumulating Polygonum species to high phosphorus exposure.

Phosphorus (P)-hyperaccumulators for phytoextraction from P-polluted areas generally show rapid growth and accumulate large amounts of P without any toxicity symptom, which depends on a range of physiological processes and gene expression patterns that have never been explored. We investigated growth, leaf element concentrations, P fractions, photosynthetic traits, and leaf metabolome and transcriptome response in amphibious P-hyperaccumulators, Polygonum hydropiper and P. lapathifolium, to high-P exposure (5 mmol L-1), with 0.05 mmol L-1 as the control. Under high-P exposure, both species demonstrated good growth, allocating more P to metabolite P and inorganic P (Pi) accompanied by high potassium and calcium. The expression of a cluster of unigenes associated with photosynthesis was maintained or increased in P. lapathifolium, explaining the increase in net photosynthetic rate and the rapid growth under high-P exposure. Metabolites of trehalose metabolism, including trehalose 6-phosphate and trehalose, were sharply increased in both species by the high-P exposure, in line with the enhanced expression of associated unigenes, indicating that trehalose metabolic pathway was closely related to high-P tolerance. These findings elucidated the physiological and molecular responses involved in the photosynthesis and trehalose metabolism in P-hyperaccumulators to high-P exposure, and provides potential regulatory pathways to improve the P-phytoextraction capability.

Root-associated bacterial microbiome shaped by root selective effects benefits phytostabilization by Athyrium wardii (Hook.).

The root-associated microbiome assembly substantially promotes (hyper)accumulator plant growth and metal accumulation and is influenced by multiple factors, especially host species and environmental stress. Athyrium wardii (Hook.) is a phytostabilizer that grows in lead (Pb)-zinc (Zn) mine tailings and shows high root Pb accumulation. However, there remains little information on the assembly of the root-associated microbiome of A. wardii and its role in phytostabilization. A field study investigated the structural and functional variation in the root-associated bacterial microbiome of Athyrium wardii (Hook.) exposed to different levels of contamination in Pb-Zn mine tailings. The root compartment dominated the variation in the root-associated bacterial microbiome but the levels of contaminants showed less impact. Bacterial co-occurrence was enhanced in the rhizosphere soil and rhizoplane but tended to be much simpler in the endosphere in terms of network complexity and connectivity. This indicates that the microbial community assembly of A. wardii was non-random and shaped by root selective effects. Proteobacteria, Chloroflexi, Actinobacteria, Cyanobacteria, and Acidobacteriota were generally the dominant bacterial phyla. The genera Crossiella and Bradyrhizobium were enriched in the rhizosphere and cyanobacterial genera were enriched in the endosphere, demonstrating substantial advantages to plant survival and adaptation in the harsh mine environment. Functional categories involved in amino acid and carbohydrate metabolism were abundant in the rhizosphere soil, thus contributing to metal solubility and bioavailability in the rhizosphere. Membrane transporters, especially ATP-binding cassette transporters, were enriched in the endosphere, indicating a potential role in metal tolerance and transportation in A. wardii. The study shows substantial variation in the structure and function of microbiomes colonizing different compartments, with the rhizosphere and endophytic microbiota potentially involved in plant metal tolerance and accumulation during phytostabilization.

Root radial apoplastic transport contributes to shoot cadmium accumulation in a high cadmium-accumulating rice line.

Radial transport of cadmium (Cd) in roots governs the amount of Cd loaded into xylem vessels, where Cd ions are translocated upward into shoots, while the mechanism of differential Cd radial transport between the high Cd-accumulating rice line Lu527-8 and the normal rice line Lu527-4 remains ambiguous. A higher Cd distribution in cross sections and root apoplast and higher bypass flow of Cd were found in Lu527-8, explaining a greater Cd translocation through the apoplastic pathway. The lower relative area of the epidermis and the constant relative area of the cortex in Lu527-8 opened-up root radial transport for Cd. Deposition of apoplastic barriers (Casparian strips and suberin lamellae) was stimulated by Cd, which effectively prevented Cd from entering the stele through the apoplastic pathway. In Lu527-8, apoplastic barriers were further from the root apex with lower expression of genes responsible for biosynthesis of Casparian strips and suberin lamellae, enhancing radial transport of Cd. Our data revealed that the higher radial apoplastic transport of Cd played an integral role in Cd translocation, contributed to a better understanding of the mechanism involved in high Cd accumulation in Lu527-8 and helped achieve the practical application of phytoextraction.

Pruned litter decomposition primes fluorine bioavailability in soils planted with different tea varieties.

Tea (Camellia sinensis L.) plant is fluoride (F) hyperaccumulator. The decomposition of pruned litter in tea plantations releases a large amount of F back into the soil. However, the effect of pruned litter return on soil F bioavailability has remained unclear. We investigated the decomposition dynamics of pruned litter from four tea varieties (Chuannong Huangyazao, Chuancha No. 3, Chuanmu No. 217 and C. sinensis 'Fuding Dabaicha') and its effect on soil F bioavailability. The decomposition of pruned litter occurred in two distinct periods, with an early period of rapid decomposition during the first 120 days, releasing 26-33 % of F, followed by a late period of slow decomposition during 120-360 days, releasing 2-9 % of F. The decomposition of pruned litter enhanced soil F bioavailability by increasing the concentrations of soil water-soluble F (WS-F), exchangeable F (EX-F), and organic matter-bound F (OR-F). The increase in WS-F, EX-F, and OR-F concentrations was higher than the amount of F released from pruned litter, suggesting that the increases in soil F availability did not solely originate from the release of F from pruned litter. The findings reveal the pathway of pruned litter decomposition priming soil F bioavailability through both the direct release of F and transformation from other fractions. Furthermore, the traits (C, N, lignin, and cellulose) of pruned litter from different tea varieties were the dominant factors controlling F release and soil F bioavailability. Compared with other tea varieties, the pruned litter of Chuanmu No. 217 with low lignin and cellulose content promoted higher mass loss and F release, resulting in the highest soil F bioavailability. These findings provide new insights into the mechanisms underlying the accumulation of bioavailable F in soil. These insights offer valuable support for devising effective management strategies for the incorporation of pruned litter into soil.

Hydrogen peroxide mediates cadmium accumulation in the root of a high cadmium-accumulating rice (Oryza sativa L.) line.

Hydrogen peroxide (H2O2) is a vital signaling molecule in response to cadmium (Cd) stress in plants. However, the role of H2O2 on Cd accumulation in root of different Cd-accumulating rice lines remains unclear. Exogenous H2O2 and 4-hydroxy-TEMPO (H2O2 scavenger) were applied to investigate the physiological and molecular mechanisms of H2O2 on Cd accumulation in the root of a high Cd-accumulating rice line Lu527-8 through hydroponic experiments. Interestingly, it was found Cd concentration in the root of Lu527-8 increased significantly when exposed to exogenous H2O2, while reduced significantly when exposed to 4-hydroxy-TEMPO under Cd stress, proving the role of H2O2 in regulating Cd accumulation in Lu527-8. Lu527-8 showed more Cd and H2O2 accumulation in the roots, along with more Cd accumulation in cell wall and soluble fraction, than the normal rice line Lu527-4. In particular, more pectin accumulation, especially low demethylated pectin, was observed in the root of Lu527-8 when exposed to exogenous H2O2 under Cd stress, resulting in more negative functional groups with greater capacity to binding Cd in the root cell wall of Lu527-8. It indicated that H2O2-induced cell wall modification and vacuolar compartmentalization contributes greatly to more Cd accumulation in the root of the high Cd-accumulating rice line.

[In-situ Remediation Effect of Cadmium-polluted Agriculture Land Using Different Amendments Under Rice-wheat Rotation].

Exploring the effects of one-time amendment treatments on cadmium (Cd)-contaminated farmland soils is beneficial for providing a theoretical basis to effectively prevent Cd pollution in farmland soils and ensure the safe production of crops. Five amendments, including straw biochar, fly ash, sepiolite, white marble powder, and shale (particle size <0.2 mm, application rate 2.25 kg·m-2), were applied to the Cd-contaminated farmland soils. The soil nutrients, pH, soil available Cd, and Cd chemical forms in the soils and grain Cd concentration in the planted crops were determined to investigate the effects and persistence of one-time applications of the five amendments. The results showed that:① the application of the five amendments had little effect on soil nutrient content, but all of them could increase soil pH. Amendment treatments improved the transfer of Cd from the acid extraction fraction to residue fraction and further reduced the Cd availability in the soil. The decreasing amplitudes of straw biochar and white marble powder soil conditioner were 20.42%-22.53%, which was higher than those in the other treatments. ② The grain Cd concentrations in rice and wheat were significantly decreased under the amendment treatments with the decreasing amplitudes of 19.88%-48.77% and 5.06%-24.00%, respectively. The Cd concentrations in rice grains under the treatments of straw biochar, fly ash, and white marble powder soil conditioner were 0.195, 0.196, and 0.223 mg·kg-1, respectively, which were lower than those under the other treatments and were close to or approached the National Standard of Food Safety(GB 2762-2017)(0.2 mg·kg-1). ③ The immobilization effects on Cd in farmland soils were decreasing with time under one-time application of the amendments. The available Cd concentrations in the soil and Cd concentrations in crop grains were still lower than those in the control after three rounds of rice-wheat rotation. The straw biochar and white marble powder soil conditioner had a good and long-term effect on reducing Cd availability in soils and Cd concentrations in crop grain, making them ideal materials for safe production in Cd-contaminated soils.

Role of Root Exudates in Cadmium Accumulation of a Low-Cadmium-Accumulating Tobacco Line (Nicotiana tabacum L.).

Root exudates are tightly linked with cadmium (Cd) uptake by the root and thus affect plant Cd accumulation. A hydroponic experiment was carried out to explore the role of root exudates in Cd accumulation of a low-Cd-accumulating tobacco line (RG11) compared with a high-Cd- accumulating tobacco line (Yuyan5). Greater secretion of organic acids and amino acids by the roots was induced by an exogenous Cd addition in the two tobacco lines. The concentration of organic acid secreted by RG11 was only 51.1~61.0% of that secreted by Yuyan5. RG11 roots secreted more oxalic acid and acetic acid and less tartaric acid, formic acid, malic acid, lactic acid, and succinic acid than Yuyan5 under Cd stress. Oxalic acid accounted for 26.8~28.8% of the total organic acids, being the most common component among the detected organic acids, and was significantly negatively correlated with Cd accumulation in RG11. Propionic acid was only detected in the root exudates of RG11 under Cd stress. Lactic acid was positively linked with Cd accumulation in Yuyan5, being less accumulated in RG11. Similarly, RG11 secreted more amino acids than Yuyan5 under Cd stress. Aspartic acid, serine, and cysteine appeared in RG11 when it was exposed to Cd. Lysine was the most secreted amino acid in RG11 under Cd stress. RG11 roots secreted less lysine, histidine, and valine, but more phenylalanine and methionine than Yuyan5 under Cd stress. The results show that organic acids and amino acids in root exudates play a key role in Cd uptake by the root, and this contribution varied with cultivar/genotype. However, further research is still needed to explore the mechanisms underlying low Cd translocation to the leaf, which may be the key contribution of low Cd accumulation in RG11 to the security of tobacco leaf.

[Stabilization Characteristics of Exogenous Cd in Different Types of Soil].

To clarify the characteristics of stabilization and availability of exogenous cadmium (Cd) in different types of soils, six main agricultural soils in Sichuan province, including acidic purple soil, neutral purple soil, calcareous purple soil, gray fluvo-aquic soil, typical yellow soil, and rinsed yellow soil, were used in this study. A soil culture experiment was conducted to explore the differences in stabilization time, chemical form, and effective Cd content between the six types of soils. Additionally, the effects of exogenous Cd on the growth and Cd accumulation of cabbage growing in different soils was discussed. The results showed the following: 1 with exogenous Cd treatment, the available Cd content of the six soils decreased sharply within 15 d after Cd addition and then tended to be flat. After 30 d, there was no significant difference. The available Cd contents of rinsed yellow soil and acidic purple soil were significantly higher than that of the other four soils, and the content of calcareous purple soil was significantly lower (1.01 mg·kg-1). 2 After stabilization, exchangeable Cd was the main Cd form in the six soils, up to 42.51%-56.07%. The relative proportions of other Cd forms differed greatly between different soils. The proportion of iron and manganese oxides in the rinsed yellow soil and typical yellow soil was higher, whereas organic complex Cd, residual Cd, and carbonate-bound Cd were higher in the gray fluvo-aquic soil, neutral purple soil, and calcareous purple soil, respectively. 3 The characteristics of availability and bioavailability of Cd among different soils were significantly different with different exogenous Cd doses. With the lowest Cd dose (0.5 mg·kg-1), compared with that in the control, there was no significant decrease in Cd content in the edible parts of the cabbage, but Cd accumulation in the edible parts differed. The Cd contents of edible parts of the cabbage growing in typical yellow soil and rinsed yellow soil were significantly higher than that of the other soils. With the highest Cd dose (2.0 mg·kg-1), the growths of cabbage growing in all six soils were significantly inhibited. The available Cd contents of rinsed yellow soil and acidic purple soil were significantly higher than that of the other four soils, which is consistent with the Cd content in the edible parts of the cabbage. The available Cd contents and the Cd content in the edible parts of the cabbage in calcareous purple soil were the lowest, and acidic soils, especially in rinsed yellow soil, had the highest.

Characterizing the rill erosion process from eroded morphology and sediment connectivity on purple soil slope with upslope earthen dike terraces.

Rills are critical venues for the transport of eroded sediments along hillslopes. The sediment transport efficiency and connectivity within hillslopes are affected by the spatiotemporal evolution of rill erosion and morphology. However, the effect of upslope sediment-laden inflow on rill erosion and connectivity remains unclear. This study investigated the variation in rill erosion from the eroded morphology and sediment connectivity using flume scouring experiments. Upslope sediment-laden inflow was simulated considering the upslope terrace areas of 0.15, 0.30, and 0.45 m2 and an upslope inflow of 6 L min-1. The quantity and cross-sectional depth of rills gradually decreased with increasing upslope terrace area. The cross-sectional morphology of rills changed from being V-shaped to U-shaped in the rill erosion process. All of the mean values of the morphological parameters gradually decreased with increasing upslope terrace area, in contrast to the width-depth ratio (Rw/d) and rill density (ρ), which both initially increased and then decreased. The average length, width, and depth of rills were smaller under an upslope terrace area of 0.45 m2 than those under an upslope terrace area of 0.15 m2; they decreased by 2.78 %, 20.67 %, and 33.68 %, respectively. Soil and water loss induced by rill erosion decreased with increasing upslope terrace area. Rills, as major venues for sediment transport on hillslopes, exhibited a higher sediment connectivity (IC) than that observed in interrill areas under the different upslope terrace areas. Rill development resulted in higher erosion between the upslope and downslope parts within rill channels. The variations in Rw/d and ρ were significantly correlated with runoff and eroded sediment yield, which could be used to estimate the rill erosion process under different upslope terrace areas.

Aggregate-associated carbon compositions explain the variation of carbon sequestration in soils after long-term planting of different tea varieties.

Strategies to increase carbon (C) sequestration in tea plantation soils are pertinent to mitigating global climate change, but little is known about the variation in C sequestration in soils planted with different tea varieties. In the current study, we collected 0-20 and 20-40 cm layer soil samples from a tea plantation planted with four tea varieties (Chuancha No.3 (CC3), Chuanmu No. 217 (CM217), Chuannong Huangyazao (CN), and C. sinensis 'Fuding Dabaicha' (FD)). Soil organic carbon (SOC) stock and composition in the bulk soil and aggregate fractions, as well as the SOC stability index (SI), were investigated. Both SOC stock and composition in the bulk soil or aggregate fractions were variable among the soils after planting different tea varieties. Overall, the highest SOC stock (0-40 cm) was observed in FD soil, followed by CN, CC3, and CM217 soil. This difference was dominated by the SOC stock associated with macroaggregates, and the highest macroaggregate-associated SOC stock was detected in FD soil in both soil layers. Moreover, FD soil showed the highest proportion of macroaggregates in both soil layers, accumulated the greatest recalcitrant organic carbon (ROC) and further contributed to the highest SI values of SOC associated with most aggregate fractions. In contrast, CN topsoil (0-20 cm) accumulated the greatest labile organic carbon (LOC) in most aggregate fractions, which had a positive correlation with the amount of C return by pruning litter. Ultimately, long-term planting of FD promoted macroaggregate formation, and ROC accumulation in aggregates greatly contributed to maintaining high C sequestration in the tea plantation soils and showed a high potential for future C budgets; in contrast, the tea plantation soil planted with CN could be a potential C source because of high C return.

Evaluation for phosphorus accumulation and removal capability of nine species in the Polygonaceae to excavate amphibious superstars used for phosphorus-phytoextraction.

Reducing excessive phosphorus (P) from both soils and eutrophic waters is attractive to achieve environmental P balance, and P-phytoextraction by amphibious plants with great biomass and P uptake is an amazing method, as already reported for P-accumulating plant, Polygonum hydropiper. However, it is still unknown how widespread high P tolerance and great P accumulation is among species in the Polygonaceae, and if there are new amphibious superstars used for P-phytoextraction. We used six Polygonum species and three non-Polygonum species to compare P accumulation and removal capability in hydroponics and soils with different P treatments. In high P hydroponics, all species showed superiority in growth and P accumulation without P toxicity, except for F. multiflora. In high P soils, all species showed much better growth performance with green leaves at 8 weeks, with shoot biomass being 3.60-29.49 g plant-1. At 8 weeks, Polygonum species displayed obviously higher shoot P accumulation (31.32-152.37 mg plant-1), P extraction ratio (3.16%-15.36%), maximum potential P removal (13.89-67.59 kg ha-1), and much lower plant effective number (7-32) than non-Polygonum species under high P soils. Besides, P. lapathifolium, P. divaricatum and P. orientale ranked the top three in growth with P concentration more than 10 mg g-1 dry weight in hydroponics and showed dominant advantage in P accumulation and P removal from high P soils. Through the cluster analysis, P. lapathifolium was always separated into a class, and P. divaricatum and P. orientale more likely clustered together. It is therefore that P. lapathifolium, P. divaricatum and P. orientale are tolerant to high P and attractive in P accumulation and P removal from high P waters and soils, and thus can be used as new amphibious superstars for P-phytoextraction, particularly P. lapathifolium.

Indigenous rhizosphere microbial community characteristics of the phytostabilizer Athyrium wardii (Hook.) grown in a Pb/Zn mine tailing.

Plant rhizosphere microbiome usually changes dramatically in adaptation to the mine environment to endure high heavy metal concentration, which in turn improves the process of revegetation and phytostabilization of mine tailing and deserves deep investigation. A field study was conducted to investigate the indigenous microbial community of a mining ecotype (ME) of the phytostabilizer Athyrium wardii (Hook.) grown in a Pb/Zn mine tailing and a corresponding non-mining ecotype (NME) grown in an uncontaminated adjacent site. Our study found a slight difference in microbial α-diversity between the ME and NME, and no significant difference between the rhizosphere and bulk soil. Both bacterial and fungal community compositions differed between the ME and NME, for which the differences were mainly driven by pH and metal contaminants. The ME harbored a unique microbial community in the rhizosphere soils different from the bulk soil and NME counterparts. The dominant phyla in the ME rhizosphere were Proteobacteria, Chloroflexi, Actinobacteria, Nitrospirae, and Ascomycota. Several genera from Proteobacteria, Acidobacteria, and Ascomycota were more abundant in the ME rhizosphere than in the NME rhizosphere. Network analysis revealed that keystone taxa were different in the two sites. Some keystone taxa from Gemmatimonadaceae, and Burkholderiaceae and Ascomycota played a critical role in microbial interactions within the mine tailing network. The unique microbial community with high tolerance in the rhizosphere soils of ME may show great benefit for plant growth and metal tolerance of the ME and thereby contributing to the process of revegetation and phytostabilization of mine tailings.

Primary seminoma of prostate in a patient with Klinefelter syndrome: A case report.

RATIONALE: Klinefelter syndrome (KS) is a sex differentiation syndrome that occurs in men and is characterized by the 47XXY genotype. An association between KS and cancer has also been reported. The occurrence of seminoma of the prostate in KS has not been reported in the literature to date. Primary seminoma should be included in the differential diagnosis of prostate neoplasms in patients with KS. PATIENT CONCERNS: A 39-year-old man presenting with urinary retention was admitted to our hospital. Physical examination revealed sparse pubic hairs, atrophic testes, and an underdeveloped penis. Hormonal examination revealed significantly lowered serum testosterone levels and markedly higher follicle-stimulating hormone levels. A chromosomal examination was performed. Computed tomography and magnetic resonance imaging imaging showed a neoplasm in the left lobe of the prostate, and immunohistochemical examination of a transrectal needle biopsy of the prostate was performed. DIAGNOSES: Chromosomal examination was exhibited a 47 XXY genotype. Histopathology and of Immunohistochemistry of the transrectal needle biopsy specimen confirmed a seminoma. No other neoplasm was found on systemic examination; therefore, the patient was diagnosed with primary prostate seminoma and Klinefelter syndrome. INTERVENTIONS: The patient refused any treatment except catheterization because of religious reason. OUTCOMES: The patient died 2 years later. LESSONS: Primary seminoma should be included in the differential diagnosis of neoplasms of the prostate in patients with KS. Transrectal ultrasound-guided prostate needle biopsy is essential for the diagnosis of prostate neoplasms, and cisplatin-based chemotherapy remains the primary treatment for seminoma.

Application of a three-dimensional visualization model in intraoperative guidance of percutaneous nephrolithotomy.

OBJECTIVES: To establish a three-dimensional visualization model of percutaneous nephrolithotomy, apply it to guiding intraoperative puncture in a mixed reality environment, and evaluate its accuracy and clinical value. METHODS: Patients with percutaneous nephrolithotomy indications were prospectively divided into three-dimensional group and control group with a ratio of 1:2. For patients in three-dimensional group, positioning markers were pasted on the skin and enhanced computed tomography scanning was performed in the prone position. Holographic three-dimensional models were made and puncture routes were planned before operation. During the operation, the three-dimensional model was displayed through HoloLens glass and visually registered with the patient's body. Puncture of the target renal calyx was performed under three-dimensional-image guiding and ultrasonic monitoring. Patients in the control group underwent routine percutaneous nephrolithotomy in the prone position under the monitoring of B-ultrasound. Deviation distance of the kidney, puncture time, puncture attempts, channel coincidence rate, stone clearance rate, and postoperative complications were assessed. RESULTS: Twenty-one and 40 patients were enrolled in three-dimensional and control group, respectively. For three-dimensional group, the average deviation between virtual and real kidney was 3.1 ± 2.9 mm. All punctures were performed according to preoperative planning. Compared with the control group, the three-dimensional group had shorter puncture time (8.9 ± 3.3 vs 14.5 ± 6.1 min, P < 0.001), fewer puncture attempts (1.4 ± 0.6 vs 2.2 ± 1.5, P = 0.009), and might also have a better performance in stone clearance rate (90.5% vs 72.5%, P = 0.19) and postoperative complications (P = 0.074). CONCLUSIONS: The percutaneous nephrolithotomy three-dimensional model manifested acceptable accuracy and good value for guiding puncture in a mixed reality environment.

Hydrogen peroxide contributes to cadmium binding on root cell wall pectin of cadmium-safe rice line (Oryza sativa L.).

Cell wall pectin is essential for cadmium (Cd) accumulation in rice roots and hydrogen peroxide (H2O2) plays an important role as a signaling molecule in cell wall modification. The role of H2O2 in Cd binding in cell wall pectin is unclear. D62B, a Cd-safe rice line, was found to show a greater Cd binding capacity in the root cell wall than a high Cd-accumulating rice line of Wujin4B. In this study, we further investigated the mechanism of the role of H2O2 in Cd binding in root cell wall pectin of D62B compared with Wujin4B. Cd treatment significantly increased the H2O2 concentration and pectin methyl esterase (PME) activity in the roots of D62B and Wujin4B by 22.45-42.44% and 12.15-15.07%, respectively. The H2O2 concentration and PME activity significantly decreased in the roots of both rice lines when H2O2 was scavenged by 4-hydroxy-Tempo. The PME activity of D62B was higher than that of Wujin4B. The concentrations of high and low methyl-esterified pectin in the roots of D62B significantly increased when exposed to Cd alone but significantly decreased when exposed to Cd and exogenous 4-hydroxy-Tempo. No significant difference was detected in Wujin4B. Exogenous 4-hydroxy-Tempo significantly decreased the Cd concentration in the cell wall pectin in both rice lines. The modification of H2O2 in Cd binding was further explored by adding H2O2. The maximum Cd adsorption amounts on the root cell walls of both rice lines were improved by exogenous H2O2·H2O2 treatment significantly influenced the relative peak area of the main functional groups (hydroxyl, carboxyl), and the groups intensely shifted after Cd adsorption in the root cell wall of D62B, while there was no significant difference in Wujin4B. In conclusion, Cd stress stimulated the production of H2O2, thus promoting pectin biosynthesis and demethylation and releasing relative functional groups involved in Cd binding on cell wall pectin, which is beneficial for Cd retention in the roots of Cd-safe rice line.

Nitric oxide amplifies cadmium binding in root cell wall of a high cadmium-accumulating rice (Oryza sativa L.) line by promoting hemicellulose synthesis and pectin demethylesterification.

Nitric oxide (NO) is tightly associated with plant response against cadmium (Cd) stress in rice since NO impacts Cd accumulation via modulating cell wall components. In the present study, we investigated that whether and how NO regulates Cd accumulation in root in two rice lines with different Cd accumulation ability. The variation of polysaccharides in root cell wall (RCW) of a high Cd-accumulating rice line Lu527-8 and a normal rice line Lu527-4 in response to Cd stress when exogenous NO supplied by sodium nitroprusside (SNP, a NO donor) was studied. Appreciable amounts of Cd distributed in RCW, in which most Cd ions were bound to pectin for the two rice lines when exposed to Cd. Exogenous NO upregulated the expression of OsPME11 and OsPME12 that were involved in pectin demethylesterification, resulting in more low methyl-esterified pectin and therefore stronger pectin-Cd binding. Exogenous NO also enhanced the concentration of hemicellulose and the amount of Cd ions in it. These results demonstrate that NO-induced more Cd binding in RCW in the two rice lines through promoting pectin demethylesterification and increasing hemicellulose accumulation. Higher OsPMEs expression and more hemicellulose synthesis contributed to more Cd immobilization in RCW of the high Cd-accumulating rice line Lu527-8. The main findings of this study reveal the regulation of NO on cell wall polysaccharides modification under Cd stress and help to elucidate the physiological and molecular mechanism of NO participating in Cd responses of rice.

Characterization of cadmium accumulation in the cell walls of leaves in a low-cadmium rice line and strengthening by foliar silicon application.

Cadmium (Cd) remobilization in leaves is affected by whether Cd is stored in nonlabile subcellular compartments, which might be regulated by silicon (Si) application. However, the underlying mechanism is still far from being completely understood. In this research, the Cd distribution pattern in leaves and a Cd-binding characterization in the cell wall of the low-Cd rice line YaHui2816 were investigated through one hydroponic experiment with 10 µM Cd in solutions. Foliar Si application was further adopted to explore its influence on the Cd accumulation in the cell walls of leaves in YaHui2816. Most of the Cd (69.4%) was distributed in the cell walls of YaHui2816 leaves, whereas the isolated cell walls of leaves from YaHui2816 exhibited a lower capacity for Cd chemisorption than the contrasting line C268A, which was resulted from its fewer relative peak areas of functional groups in the cell wall, such as carboxyl CO and OH stretching. Foliar Si application significantly increased the Cd concentration in leaves and various cell wall fractions (pectin, hemicellulose 1 and residue) by 191% and 137-160%, respectively. RNA-seq analysis revealed that foliar Si application depressed the expression of the metal transporters OsZIP7 and OsZIP8, up-regulated the expression of genes participating in the glutathione metabolism and the cellulose synthesis. Overall, the influence of foliar Si application on Cd-accumulation in the cell wall of leaves in a low-Cd rice line was demonstrated in this research, which inspires further avenues to ensure the food safety of rice grains.

A composite amendment benefits rice (Oryza sativa L.) safety and production in cadmium-contaminated soils by unique characteristics after oxidation modification.

In-situ immobilization is an effective strategy for Cd remediation and food safety, while some modifications are necessary to improve immobilization efficiency. In this study, a composite amendment (RFW) derived from rice straw biochar (RSB), fly ash (FA), and white marble (WM) was modified by oxidization (RFW-O) and pyrolysis (RFW-P). The RFW-O showed stronger Cd2+ sorption ability than RFW and RFW-P due to larger BET surface area and more oxygen containing-functional groups. Complexation and iron exchange were the two main processes of Cd2+ sorption on RFW-O. As a result, the application of RFW-O significantly reduced Cd availability in soils by 10.11-26.24% along with increased soil pH. It was found to be optimal to apply the RFW-O at a dosage of 2.5 wt% for 15 days before transplantation. After RFW-O application, Cd concentrations in brown rice decreased by 40.49% and 41.59% for pot and field experiment, respectively, and were less than 0.2 mg kg-1. The catalase, dehydrogenase, acid phosphatase and alkaline phosphatase activities in soils increased significantly. Moreover, RFW-O showed no significant effect on rice yield and quality. The RFW-O is thereby considered to be an ideal amendment for in-situ immobilization of Cd-contaminated soils for rice safety and production in practice.

The changes of rhizosphere characteristics contributed to enhanced Pb accumulation in Athyrium wardii (Hook.) Makino after nitrilotriacetic acid application.

Chelant-assisted phytoremediation may modify plant rhizosphere, which is closely related to heavy metal (HM) accumulation in plants. This work focused on the effects of nitrilotriacetic acid (NTA) on rhizosphere characteristics to investigate the mechanisms of lead (Pb) accumulation in Athyrium wardii (Hook.) Makino with exposure to 800 mg kg-1 Pb. After NTA application, Pb accumulation in the underground part of A. wardii increased by 14.3%, accompanying with some changes for the rhizosphere soils. Soil pH decreased by 0.37 units, and the dissolved organic carbon (DOC) content in the rhizosphere soils significantly increased by 7.6%. The urease, acid phosphatase, and catalase activities in the rhizosphere soils significantly increased by 104.8%, 19.7%, and 27.1%, respectively. However, a slight inhibition on microbial activities was observed in the rhizosphere of A. wardii after NTA application. Soil respiration decreased by 8.9%, and microbial biomass carbon decreased by 8.9% in the rhizosphere soils, indicating that NTA addition might recruit some microorganisms to maintain rhizosphere functions in Pb-contaminated soils while inhibiting others with low tolerance to Pb. Results suggest that lower pH, more DOC exudation, and higher soil enzyme activities after NTA application contributed to the increase of Pb accumulation in A. wardii. This study gave some preliminary evidence for NTA-assisted Pb remediation by A. wardii by modifying rhizosphere characteristics.