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.

A scientometric analysis of research trends on targeting mTOR in breast cancer from 2012 to 2022.

Over the past decade, thousands of articles have been published on the mechanistic target of rapamycin (mTOR) and its role in breast cancer. However, the variability and heterogeneity of academic data may impact the acquisition of published research information. Due to the large number, heterogeneity, and varying quality of publications related to mTOR and breast cancer, sorting out the present state of the research in this area is critical for both researchers and clinicians. Therefore, scientometric techniques and visualization tools were employed to analyze the large number of bibliographic metadata related to the research area of mTOR and breast cancer. The features of relevant publications were searched from 2012 to 2022 to evaluate the present status of research and the evolution of research hotspots in this particular field. Web of Science was utilized to extract all relevant publications from 2012 to 2022. Subsequently, Biblioshiny and VOSviewer were utilized to obtain data on the most productive countries, authors, and institutions, annual publications and citations, the most influential journals and articles, and the most frequently occurring keywords. In total, 1,471 publications were retrieved, comprising 1,167 original articles and 304 reviews. There was a significant rise in publications between 2015 and 2018, followed by a sharp decline in 2019 and a rebound since then. The publication with the highest number of citations was a 2012 review authored by Baselga et al. The United States had the highest number of publications, citations and connections among all countries. Oncotarget had the highest number of published articles among all the journals, and José Baselga had the strongest links with other authors. Excluding the search topics, the most frequently used words were "expression" (n = 297), "growth" (n = 228), "activation" (n = 223), "pathway" (n = 205), and "apoptosis" (n = 195). mTOR is crucially involved in breast cancer pathogenesis, but its exact mechanism of action remains controversial and warrants further investigation. The scientometric analysis provides a distinct overview of the existing state of research and highlights the topical issues that deserve further exploration.

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.

Factors predicting recurrence after left­sided pancreatectomy for pancreatic ductal adenocarcinoma.

BACKGROUND: Recurrence after resection is the main factor for poor survival. The relationship between clinicopathological factors and recurrence after curative distal pancreatectomy for PDAC has rarely been reported separately. METHODS: Patients with PDAC after left­sided pancreatectomy between May 2015 and August 2021 were retrospectively identified. RESULTS: One hundred forty-one patients were included. Recurrence was observed in 97 patients (68.8%), while 44 (31.2%) patients had no recurrence. The median RFS was 8.8 months. The median OS was 24.9 months. Local recurrence was the predominant first detected recurrence site (n = 36, 37.1%), closely followed by liver recurrence (n = 35, 36.1%). Multiple recurrences occurred in 16 (16.5%) patients, peritoneal recurrence in 6 (6.2%) patients, and lung recurrence in 4 (4.1%) patients. High CA19-9 value after surgery, poor differentiation grade, and positive lymph nodes were found to be independently associated with recurrence. The patients receiving adjuvant chemotherapy had a decreased likelihood of recurrence. In the high CA19-9 value cohort, the median PFS and OS of the patients with or without chemotherapy were 8.0 VS. 5.7 months and 15.6 VS. 13.8 months, respectively. In the normal CA19-9 value cohort, there was no significant difference in PFS with or without chemotherapy (11.7 VS. 10.0 months, P = 0.147). However, OS was significantly longer in the patients with chemotherapy (26.4 VS. 13.8 months, P = 0.019). CONCLUSIONS: Tumor biologic characteristics, such as T stage, tumor differentiation and positive lymph nodes, affecting CA19-9 value after surgery are associated with patterns and timing of recurrence. Adjuvant chemotherapy significantly reduced recurrence and improved survival. Chemotherapy is strongly recommended in patients with high CA199 after surgery.

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.

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.

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.

Direct nitrogen interception from chitin/chitosan for imidazo[1,5-a]pyridines.

A catalyst-free one-pot methodology that enables direct nitrogen interception of chitosan/chitin for imidazo[1,5-a]pyridines was developed. This strategy features direct synthesis of important deuterated imidazo[1,5-a]pyridines and tridentate ligands. In particular, a broad group of previously inaccessible products including saturated 1-alkylimidazo[1,5-a]pyridines are unprecedently synthesized by this protocol.

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.

Towards a native environment: structure and function of membrane proteins in lipid bilayers by NMR.

Solid-state NMR (ssNMR) is a versatile technique that can be used for the characterization of various materials, ranging from small molecules to biological samples, including membrane proteins. ssNMR can probe both the structure and dynamics of membrane proteins, revealing protein function in a near-native lipid bilayer environment. The main limitation of the method is spectral resolution and sensitivity, however recent developments in ssNMR hardware, including the commercialization of 28 T magnets (1.2 GHz proton frequency) and ultrafast MAS spinning (<100 kHz) promise to accelerate acquisition, while reducing sample requirement, both of which are critical to membrane protein studies. Here, we review recent advances in ssNMR methodology used for structure determination of membrane proteins in native and mimetic environments, as well as the study of protein functions such as protein dynamics, and interactions with ligands, lipids and cholesterol.

The role of polysaccharides functional groups in cadmium binding in root cell wall of a cadmium-safe rice line.

Exploring the mechanism of cadmium (Cd) accumulation in Cd-safe rice lines is beneficial for ensuring rice safety. D62B, a Cd-safe rice line, accumulates less than 0.2 mg Cd kg-1 in the brown rice due to strong capacity of Cd retention in the roots, and the root cell wall (RCW) polysaccharides play important roles. However, specific underlying mechanism of Cd binding on the polysaccharides is little known. In this study, the role of polysaccharides, especially pectin and hemicellulose 1 (HC1), in RCW of D62B was investigated by adsorption experiments and Fourier Transform Infrared Spectroscopy (FTIR) analysis compared with a common rice line (Luhui17). Cadmium was adsorbed on RCW of two rice lines by a multilayer and inhomogeneous chemisorption way with the force of ion transfer or exchange. Cadmium was adsorbed on RCW rapidly at first stage with the limit of internal and external diffusion, and gradually reached saturation. With the removal of pectin, the Cd adsorption rate, maximum Cd adsorption amount and the shift degree of carboxyl groups in the RCW of D62B sharply decreased, which showed advantages compared with Luhui17. Sequential removal of HC1 further decreased the maximum Cd adsorption amount and the shift degree of hydroxyl groups. The results showed that more available functional groups, especially carboxyl groups in pectin and hydroxyl groups in HC1, contributed to Cd immobilization within the RCW of Cd-safe rice line, thus limiting Cd translocation to the shoot and reducing Cd accumulation in the brown rice.

A transcriptomic view of cadmium retention in roots of cadmium-safe rice line (Oryza sativa L.).

A better understanding of the mechanisms controlling cadmium (Cd) accumulation in rice will benefit the development of strategies to minimize Cd accumulation in grains. A Cd-safe rice line designated D62B accumulated less than 0.2 mg Cd kg-1 in brown rice due to its strong capacity for Cd retention in roots. Here transcriptomic was used to clarify the underlying mechanisms of Cd response in roots of D62B compared with a high Cd-accumulating line (Wujin4B). There were 777, 1058 differentially expressed genes (DEGs) in D62B and Wujin4B, respectively, when exposed to Cd. The functions of DEGs were clearly line-specific. Cell wall biosynthesis responded more intensively to Cd stress in D62B, facilitating Cd restriction. Meanwhile, more glutathione (GSH) and phytochelatins synthesized in D62B with the upregulation of sulphur and GSH metabolism. Besides, membrane proteins played critical roles in Cd response in D62B, whereas 18 terms involved in regulation were enriched in Wujin4B. Exogenous GSH further induced the expression of genes related to GSH metabolism and cell wall biosynthesis, leading to the retention of more Cd. Great responsiveness of cell wall biosynthesis and GSH metabolism could be considered the most important specific mechanisms for Cd retention in the roots of Cd-safe rice line.