Arsenic (As) is one of the most toxic environmental contaminants that is ubiquitously distributed in the environment. Millions of people worldwide suffer from As poisoning due to As exposure from ...drinking water and dietary intake. Reducing As accumulation in food crops is of great importance for food safety and public health. Limiting As accumulation in food crops or phytoremediation of As-contaminated soil depend on a detailed understanding of As uptake and transport in plants. Plants take up and transport different As species via various membrane transporters that are localized in different tissues or cell types and with different orientations. Many of these transporters are responsible for the uptake and translocation of essential or beneficial nutrients, but can also transport As species inadvertently due to imperfect selectivity. Herein, we summarize the roles of transporters involved in the uptake, transport, accumulation and detoxification of different As species and the regulation mechanisms of these transporters in plants. Potential uses of these transporters for breeding or genetic engineering crops of low As accumulation or plants for phytoremediation are also discussed.
Methylarsenite (MAs(III)), a product of arsenic biomethylation or bioreduction of methylarsenate (MAs(V)), has been proposed as a primitive antibiotic. However, the antibacterial property and the ...bactericidal mechanism of MAs(III) remain largely unclear. In this study, we found that MAs(III) is highly toxic to 14 strains of bacteria, especially against 9 strains of Gram‐positive bacteria with half maximal inhibitory concentration (IC50) in the sub micromolar range for Staphyloccocus aureus, Microbacterium sp., Pseudarthrobacter siccitolerans and several Bacillus species. In a co‐culture of B. subtilis 168 and MAs(III)‐producer Enterobacter sp. CZ‐1, the later reduced non‐toxic MAs(V) to highly toxic MAs(III) to kill the former and gain a competitive advantage. MAs(III) induced autolysis of B. subtilis 168. Deletion of the autolysins LytC, LytD, LytE, and LytF suppressed MAs(III)‐induced autolysis in B. subtilis 168. Transcriptomic analysis showed that MAs(III) downregulated the expression of the major genes involved in the biosynthesis of the cell wall peptidoglycan. Overexpression of an UDP‐N‐acetylglucosamine enolpyruvyl transferase gene murAA alleviated MAs(III)‐induced autolysis in B. subtilis 168. MAs(III) disrupted the membrane potential of B. subtilis 168 and caused severe membrane damage. The results suggest that MAs(III) is a broad‐spectrum antibiotic preferentially against Gram‐positive bacteria by disrupting the cell wall biosynthesis pathway and cell membrane potential.
Sedum plumbizincicola is able to hyperaccumulate cadmium (Cd), a nonessential and highly toxic metal, in the above‐ground tissues, but the mechanisms for its Cd hypertolerance are not fully ...understood. Here, we show that the heavy metal ATPase 1 (SpHMA1) of S. plumbizincicola plays an important role in chloroplast Cd detoxification. Compared with the HMA1 ortholog in the Cd nonhyperaccumulating ecotype of Sedum alfredii, the expression of SpHMA1 in the leaves of S. plumbizincicola was >200 times higher. Heterologous expression of SpHMA1 in Saccharomyces cerevisiae increased Cd sensitivity and Cd transport activity in the yeast cells. The SpHMA1 protein was localized to the chloroplast envelope. SpHMA1 RNA interference transgenic plants and CRISPR/Cas9‐induced mutant lines showed significantly increased Cd accumulation in the chloroplasts compared with wild‐type plants. Chlorophyll fluorescence imaging analysis revealed that the photosystem II of SpHMA1 knockdown and knockout lines suffered from a much higher degree of Cd toxicity than wild type. Taken together, these results suggest that SpHMA1 functions as a chloroplast Cd exporter and protects photosynthesis by preventing Cd accumulation in the chloroplast in S. plumbizincicola and hyperexpression of SpHMA1 is an important component contributing to Cd hypertolerance in S. plumbizincicola.
Cadmium is a highly toxic metal and accumulates in the leaves to very high levels in Cd hyperaccumulators in Sedum plumbizincicola, posing a high risk of Cd toxicity to the chloroplasts. In this study, we demonstrate that SpHMA1 is a Cd exporter localized to the chloroplast envelope, functioning to detoxify Cd in the chloroplasts to protect photosynthetic reactions in S. plumbizincicola. The hyperexpression of SpHMA1 in the leaves of S. plumbizincicola, compared with SaHMA1n in a nonhyperaccumulating ecotype S. alfredii, likely confers an adaptive advantage under Cd stress conditions and contributes to Cd hypertolerance in S. plumbizincicola. These novel findings have important implications for the evolution of metal hyperaccumulation phenotype and the adaptation of plants to metal‐contaminated environments.
Aim
To synthesize the effects of theory‐based self‐management educational interventions on patients with type 2 diabetes (T2DM) in randomized controlled trials.
Background
Type 2 diabetes is a common ...chronic disease causing complications that put a heavy burden on society and reduce the quality of life of patients. Good self‐management of diabetes can prevent complications and improve the quality of life of T2DM patients.
Design
Systematic review with meta‐analysis of randomized controlled trials following Cochrane methods.
Data resources
A literature search was carried out in the MEDLINE, EMBASE, CINAHL, PSYCINFO, and Web of Science databases (1980–April 2015).
Review methods
The risk of bias of these eligible studies was assessed independently by two authors using the Cochrane Collaboration's tool. The Publication bias of the main outcomes was examined. Statistical heterogeneity and random‐effects model were used for meta‐analysis.
Results
Twenty studies with 5802 participants met the inclusion criteria. The interventions in the studies were based on one or more theories which mostly belong to mid‐range theories. The pooled main outcomes by random‐effects model showed significant improvements in HbA1c, self‐efficacy, and diabetes knowledge, but not in BMI. As for quality of life, no conclusions can be drawn as the pooled outcome became the opposite with reduced heterogeneity after one study was excluded. No significant publication bias was found in the main outcomes.
Conclusion
To get theory‐based interventions to produce more effects, the role of patients should be more involved and stronger and the education team should be trained beyond the primary preparation for the self‐management education program.
Plants take up a wide range of trace metals/metalloids (hereinafter referred to as trace metals) from the soil, some of which are essential but become toxic at high concentrations (e.g., Cu, Zn, Ni, ...Co), while others are non‐essential and toxic even at relatively low concentrations (e.g., As, Cd, Cr, Pb, and Hg). Soil contamination of trace metals is an increasing problem worldwide due to intensifying human activities. Trace metal contamination can cause toxicity and growth inhibition in plants, as well as accumulation in the edible parts to levels that threatens food safety and human health. Understanding the mechanisms of trace metal toxicity and how plants respond to trace metal stress is important for improving plant growth and food safety in contaminated soils. The accumulation of excess trace metals in plants can cause oxidative stress, genotoxicity, programmed cell death, and disturbance in multiple physiological processes. Plants have evolved various strategies to detoxify trace metals through cell‐wall binding, complexation, vacuolar sequestration, efflux, and translocation. Multiple signal transduction pathways and regulatory responses are involved in plants challenged with trace metal stresses. In this review, we discuss the recent progress in understanding the molecular mechanisms involved in trace metal toxicity, detoxification, and regulation, as well as strategies to enhance plant resistance to trace metal stresses and reduce toxic metal accumulation in food crops.
Contamination of soil with trace metals/metalloids can cause toxicity to plants and threaten food safety. This review presents recent progress in understanding the molecular mechanisms of trace metal/metalloid toxicity and detoxification, and strategies to enhance plant resistance to trace metal stresses and reduce toxic metal accumulation in food crops.
Rapid industrialization in China in recent decades has resulted in soil contamination in some areas, raising the concern about food safety. Consumption of rice represents a major exposure route for ...the toxic elements cadmium (Cd) and arsenic (As). We collected 160 polished rice from local markets in 20 provinces in China and determined total Cd and As concentrations and As speciation. Total Cd concentration ranged from below the detection limit to 0.77 mg kg−1, with 10% of the samples exceeding the Chinese limit (0.2 mg kg−1). Rice Cd concentration showed a distinct geographical pattern, increasing from low levels in the north to high levels in the south of China. Median daily Cd intake from rice varied from 0.01 μg kg−1 body weight in the north to 0.61 μg kg−1 body weight in the south of China, representing between 1% and 73% of the tolerable daily intake (TDI) recommended by FAO/WHO. The highest median Cd intake from rice was in Hunan province with 2 times TDI. Total As concentration ranged from 0.011 to 0.186 mg kg−1, with inorganic As (iAs) and dimethylarsinic acid (DMAs) on average accounting for 69% and 31%, respectively. All samples were below the Chinese limit for iAs in rice (0.2 mg kg−1). There was no clear geographical pattern in rice total As concentration, but rice produced in northeastern China contained higher percentages of DMAs and lower percentages of iAs. This study highlights a high risk of Cd exposure from rice consumption for the population of southern China and suggested strategies for reducing Cd accumulation in rice crop.
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•160 polished rice samples were collected from local markets in 20 provinces in China.•Rice Cd concentration showed an increasing trend from north to south of China.•Dietary Cd intake from rice was high in the population in southern China.•Rice total As showed no clear geographical pattern, but rice methylated As% was higher in northeast China.
High Cd concentrations are found in rice samples from southern China, posing a high risk of Cd exposure from rice consumption for population in the region.
Soil contamination in some areas of southern China has resulted in elevated dietary intake of cadmium (Cd), posing a potential risk to human health. A survey of paired soil-rice (n = 200) and ...soil-vegetable (n = 142) samples was conducted in Xiangtan county of Hunan province, southern China. The concentrations of Cd in all the samples were determined by inductively coupled plasma mass spectrometry. Dietary intakes of Cd from the consumption of locally produced rice and vegetables were estimated for different age groups. Among the 342 crop samples collected in the survey, 88% and 29% of rice grain and vegetable samples, respectively, exceeded the Chinese maximum permissible limit for Cd (0.2 mg dry weight kg−1, 0.2 mg fresh weight kg−1 and 0.1 mg fresh weight kg−1 for rice, leafy vegetables and for rootstalk and legume vegetables, respectively). The median dietary Cd intake varied from 66.5 to 116 μg Cd kg−1 body weight (BW) month−1, with children (4–11 years) exhibiting the highest intake. These values are 2.7–4.6 times the tolerable dietary intake of 25 μg kg−1 BW month−1 recommended by the Joint FAO/WHO Expert Committee on Food Additives. For the general population in Xiangtan county, rice contributed the majority (81%) of the Cd intake with vegetables contributing only 19%. The median hazard quotient calculated from dietary Cd intake was 2.4 times the permissible level, indicating a high risk to the local residents. This study highlights an urgent need to reduce the transfer of Cd from soil to the food chain in the investigated region.
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•A paired soil-crop survey was conducted in a county in southern China.•82% of the soil samples exceeded the Chinese soil Cd threshold.•88% and 29% of rice and vegetable samples exceeded the Chinese limits for Cd.•Median Cd intake from rice and vegetables was 2.7–4.6 times the FAO/WHO guideline.
• Inorganic arsenic (iAs) is a ubiquitous human carcinogen, and rice (Oryza sativa) is the main contributor to iAs in the diet. Methylated pentavalent As species are less toxic and are routinely ...found in plants; however, it is currently unknown whether plants are able to methylate As. • Rice, tomato (Solanum lycopersicum) and red clover (Trifolium pratense) were exposed to iAs, monomethylarsonic acid (MMA(V)), or dimethylarsinic acid (DMA(V)), under axenic conditions. Rice seedlings were also grown in two soils under nonsterile flooded conditions, and rice plants exposed to arsenite or DMA(V) were grown to maturity in nonsterile hydroponic culture. Arsenic speciation in samples was determined by HPLC‐ICP‐MS. • Methylated arsenicals were not found in the three plant species exposed to iAs under axenic conditions. Axenically grown rice was able to take up MMA(V) or DMA(V), and reduce MMA(V) to MMA(III) but not convert it to DMA(V). Methylated As was detected in the shoots of soil‐grown rice, and in rice grain from nonsterile hydroponic culture. GeoChip analysis of microbial genes in a Bangladeshi paddy soil showed the presence of the microbial As methyltransferase gene arsM. • Our results suggest that plants are unable to methylate iAs, and instead take up methylated As produced by microorganisms.
Many infections and stress signals can rapidly activate the NLRP3 inflammasome to elicit robust inflammatory responses. This activation requires a priming step, which is thought to be mainly for ...upregulating NLRP3 transcription. However, recent studies report that the NLRP3 inflammasome can be activated independently of transcription, suggesting that the priming process has unknown essential regulatory steps. Here, we report that JNK1-mediated NLRP3 phosphorylation at S194 is a critical priming event and is essential for NLRP3 inflammasome activation. We show that NLRP3 inflammasome activation is disrupted in NLRP3-S194A knockin mice. JNK1-mediated NLRP3 S194 phosphorylation is critical for NLRP3 deubiquitination and facilitates its self-association and the subsequent inflammasome assembly. Importantly, we demonstrate that blocking S194 phosphorylation prevents NLRP3 inflammasome activation in cryopyrin-associated periodic syndromes (CAPS). Thus, our study reveals a key priming molecular event that is a prerequisite for NLRP3 inflammasome activation. Inhibiting NLRP3 phosphorylation could be an effective treatment for NLRP3-related diseases.
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•Phosphorylation of NLRP3 at S194 is a key priming event for inflammasome activation•JNK1 directly phosphorylates NLRP3•S194 phosphorylation facilitates the self-association of NLRP3•Inhibiting NLRP3 phosphorylation could be a treatment for NLRP3-related diseases
The NLRP3 inflammasome activation requires a priming process; however, the mechanism remains obscure. Song et al. demonstrate that JNK1-mediated NLRP3 phosphorylation is a key molecular priming event that poises NLRP3 for its self-association and inflammasome assembly. This study suggests that inhibiting NLRP3 phosphorylation could be utilized in treating NLRP3-related diseases.
• How cadmium (Cd) tolerance in rice is regulated remains poorly understood. We used a forward genetic approach to investigate Cd tolerance in rice.
• Using a root elongation assay, we isolated a ...rice mutant with enhanced Cd tolerance, cadt1, from an ethyl methanesulphonate (EMS)-mutagenized population of a widely grown Indica cultivar. The mutant accumulated more Cd in roots but not in shoots and grains. Using genomic resequencing and complementation, we identified OsCADT1 as the causal gene for the mutant phenotype, which encodes a putative serine hydroxymethyltransferase.
• OsCADT1 protein was localized to the nucleus and the OsCADT1 gene was expressed in both roots and shoots. OsCADT1 mutation resulted in higher sulphur and selenium accumulation in the shoots and grains. Selenate influx in cadt1 was 2.4 times that of the wild-type. The mutant showed higher expression of the sulphate/selenate transporter gene OsSULTR1;1 and the sulphur-deficiency-inducible gene OsSDI1. Thiol compounds including cysteine, glutathione and phytochelatins were significantly increased in the mutant, underlying its increased Cd tolerance. Growth and grain biomass were little affected.
• The results suggest that OsCADT1 acts as a negative regulator of sulphate/selenate uptake and assimilation. OsCADT1 mutation increases Cd tolerance and enriches selenium in rice grains, providing a novel solution for selenium biofortification.
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