Arsenic, cadmium, lead, and mercury are toxic elements that are almost ubiquitously present at low levels in the environment because of anthropogenic influences. Dietary intake of plant-derived food ...represents a major fraction of potentially health-threatening human exposure, especially to arsenic and cadmium. In the interest of better food safety, it is important to reduce toxic element accumulation in crops. A molecular understanding of the pathways responsible for this accumulation can enable the development of crop varieties with strongly reduced concentrations of toxic elements in their edible parts. Such understanding is rapidly progressing for arsenic and cadmium but is in its infancy for lead and mercury. Basic discoveries have been made in
Arabidopsis
, rice, and other models, and most advances in crops have been made in rice. Proteins mediating the uptake of arsenic and cadmium have been identified, and the speciation and biotransformations of arsenic are now understood. Factors controlling the efficiency of root-to-shoot translocation and the partitioning of toxic elements through the rice node have also been identified.
•Graminaceous plants have highly developed and organized vascular system in the nodes.•Inter-vascular transfer in nodes largely contributes to mineral nutrient distribution.•Four different strategies ...in nodes for different elements distribution are identified.
Mineral elements, including both essential and toxic elements, are delivered to different tissues after they are taken up from the roots, but the mechanism (or mechanisms) underlying the distribution remains poorly understood. In graminaceous plants, this distribution occurs in nodes, which have a complex, well-organized vascular system. A transfer of mineral elements between different vascular bundles is required, especially for preferential distribution to developing tissues that have low transpiration but high nutrient requirements. This intervascular transfer is mediated by various transporters localized at different cells in the node. In this opinion article, we propose four modes of distribution for different mineral elements: xylem-switch, phloem-tropic, phloem-kickback, and minimum-shift, based on specific molecular transport processes identified in the nodes mainly of rice (Oryza sativa). We also discuss the prospects for future studies on mineral nutrient distribution in the nodes.
Summary
Ammonium is a preferential nitrogen form for rice (Oryza sativa) grown in paddy field, but the molecular mechanisms for ammonium uptake have not been well understood.
We functionally ...characterized three members belonging to ammonium transporter 1 (AMT1) and investigated their contributions to ammonium uptake.
Spatial expression analysis showed that the upregulated expression of OsAMT1;1 and OsAMT1;2 and downregulated expression of OsAMT1;3 by ammonium were higher in the root mature region than in the root tips. All OsAMT1 members were polarly localized at the distal side of exodermis in the mature region of crown roots and lateral roots. Upon exposure to ammonium, localization of OsAMT1;1 and OsAMT1;2 was also observed in the endoplasmic reticulum, but their abundance in the plasma membrane was not changed. Single knockout of either gene did not affect ammonium uptake, but knockout of all three genes resulted in 95% reduction of ammonium uptake. However, the nitrogen uptake did not differ between the wild‐type rice and triple mutants at high ammonium and nitrate supply.
Our results indicate that three OsAMT1 members are cooperatively required for uptake of low ammonium in rice roots and that they undergo a distinct regulatory mechanism in response to ammonium.
Summary
Iron (Fe) from rice grains is an important source of dietary intake; however, the molecular mechanisms responsible for loading of Fe to the grains are poorly understood.
We functionally ...characterized a vacuolar iron transporter gene, OsVIT2 in terms of expression pattern, cellular localization, and mutant phenotypes.
OsVIT2 was expressed in the parenchyma cell bridges of nodes, in the mestome sheath of leaf sheath and aleurone of the caryopsis. Mutation of OsVIT2 resulted in decreased Fe distribution to the leaf sheath, nodes, and aleurone, but increased Fe to the leaf blade and grains. Furthermore, Fe was heavily deposited in the parenchyma cell bridges, mestome sheath and aleurone in the wild‐type rice, but this accumulation was decreased in the knockout lines. Conversely, heavier deposition of Fe was observed in the embryo and endosperm of the grains of knockout lines compared with the wild‐type rice, resulting in increased Fe accumulation in the polished rice without yield penalty.
These results indicate that OsVIT2 is involved in the distribution of Fe to the grains through sequestering Fe into vacuoles in mestome sheath, nodes, and aleurone layer and that knockout of this gene provides a potential way for Fe biofortification without yield penalty.
Hepatitis D virus (HDV) is a defective virus that completes its life cycle only with hepatitis B virus (HBV). The HBV with HDV super-infection has been considered as one of the most severe forms of ...the chronic viral hepatitis. However, there is a scarcity of data on the global burden of HDV infection.
We searched PubMed, Embase, Cochrane Library and China Knowledge Resource Integrated databases from 1 January 1977 to 31 December 2016. We included studies with a minimum sample size of 50 patients. Our study analysed data from a total of 40 million individuals to estimate the prevalence of HDV by using Der-Simonian Laird random-effects model. The data were further categorised according to risk factors.
From a total of 2717 initially identified studies, only 182 articles from 61 countries and regions met the final inclusion criteria. The overall prevalence of HDV was 0.98% (95% CI 0.61 to 1.42). In HBsAg-positive population, HDV pooled prevalence was 14.57% (95% CI 12.93 to 16.27): Seroprevalence was 10.58% (95% CI 9.14 to 12.11) in mixed population without risk factors of intravenous drug use (IVDU) and high-risk sexual behaviour (HRSB). It was 37.57% (95% CI 29.30 to 46.20) in the IVDU population and 17.01% (95% CI 10.69 to 24.34) in HRSB population.
We found that approximately 10.58% HBsAg carriers (without IVDU and HRSB) were coinfected with HDV, which is twofold of what has been estimated before. We also noted a substantially higher HDV prevalence in the IVDU and HRSB population. Our study highlights the need for increased focus on the routine HDV screening and rigorous implementation of HBV vaccine programme.
Identifying the clinical implications and modifiable and unmodifiable factors of aging requires the measurement of biological age (BA) and age gap. Leveraging the biomedical traits involved with ...physical measures, biochemical assays, genomic data, and cognitive functions from the healthy participants in the UK Biobank, we establish an integrative BA model consisting of multi‐dimensional indicators. Accelerated aging (age gap >3.2 years) at baseline is associated incident circulatory diseases, related chronic disorders, all‐cause, and cause‐specific mortality. We identify 35 modifiable factors for age gap (p < 4.81 × 10−4), where pulmonary functions, body mass, hand grip strength, basal metabolic rate, estimated glomerular filtration rate, and C‐reactive protein show the most significant associations. Genetic analyses replicate the possible associations between age gap and health‐related outcomes and further identify CST3 as an essential gene for biological aging, which is highly expressed in the brain and is associated with immune and metabolic traits. Our study profiles the landscape of biological aging and provides insights into the preventive strategies and therapeutic targets for aging.
The study included 59,316 healthy participants in the UK Biobank and considered 8276 phenotypes for developing biological age model. LightGBM algorithm was conducted to identify the most important predictors for biological age and build the model and the top 20 predictors were selected. We tested the longitudinal associations of age gap with 70 common health‐related outcomes, all‐cause mortality and cause‐specific mortality, and the genetic correlations of age gap with common health‐related outcomes. We identified 34 modifiable factors and 9 genomic risk loci for age gap and profiled the pleiotropy of rs3761280 in the UK Biobank.
Silicon (Si) is not classified as an essential plant nutrient, and yet numerous reports have shown its beneficial effects in a variety of species and environmental circumstances. This has created ...much confusion in the scientific community with respect to its biological roles. Here, we link molecular and phenotypic data to better classify Si transport, and critically summarize the current state of understanding of the roles of Si in higher plants. We argue that much of the empirical evidence, in particular that derived from recent functional genomics, is at odds with many of the mechanistic assertions surrounding Si’s role. In essence, these data do not support reports that Si affects a wide range of molecular-genetic, biochemical and physiological processes. A major reinterpretation of Si’s role is therefore needed, which is critical to guide future studies and inform agricultural practice. We propose a working model, which we term the ‘apoplastic obstruction hypothesis’, which attempts to unify the various observations on Si’s beneficial influences on plant growth and yield. This model argues for a fundamental role of Si as an extracellular prophylactic agent against biotic and abiotic stresses (as opposed to an active cellular agent), with important cascading effects on plant form and function.
Summary
Inter‐vascular transfer in rice (Oryza sativa) nodes is required for delivering mineral elements to developing tissues, which is mediated by various transporters in the nodes. However, the ...effect of these transporters on distribution of mineral elements in the nodes at a cellular level is still unknown. Here, we established a protocol for bioimaging of multiple elements at a cellular level in rice node by laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS), and compared the mineral distribution profile between wild‐type (WT) rice and mutants. Both relative comparison of mineral distribution normalized by endogenous 13C and quantitative analysis using spiked standards combined with soft ablation gave valid results. Overall, macro‐nutrients such as K and Mg were accumulated more in the phloem region, while micro‐nutrients such as Fe and Zn were highly accumulated at the inter‐vascular tissues of the node. In mutants of nodal Zn transporter OsHMA2, Zn localization pattern in the node tissues did not differ from that of WT; however, Zn accumulation in the inter‐vascular tissues was lower in uppermost node I but higher in the third upper node III compared with the WT. In contrast, Si deposition in the mutants of three nodal Si transporters Lsi2, Lsi3 and Lsi6 showed different patterns, which are consistent with the localization of these transporters. This improved LA‐ICP‐MS analysis combined with functional characterization of transporters will provide further insight into mineral element distribution mechanisms in rice and other plant species.
Significance Statement
We established a method with laser ablation‐inductively coupled plasma‐mass spectrometry for multi‐elemental imaging at a cellular level in rice node as well as root and leaf tissues. This method is characterized by high‐resolution, easy accessibility, low running cost. Normalization by endogenous 13C makes different samples comparable. Furthermore, combination of spiked cryo‐compound of standards with soft ablation technique gave quantitative results for each element. This technique will be a powerful tool for linking transporter localization to element distribution at a cellular level.
Metabolomics offers a noninvasive methodology to identify metabolic markers for pathogenesis and diagnosis of diseases. This work aimed to characterize circulating metabolic signatures of benign ...thyroid nodule (BTN) and papillary thyroid carcinoma (PTC) via serum‐plasma matched metabolomics. A cohort of 1,540 serum‐plasma matched samples and 114 tissues were obtained from healthy volunteers, BTN and PTC patients enrolled from 6 independent centers. Untargeted metabolomics was determined by liquid chromatography‐quadrupole time‐of‐flight mass spectrometric and multivariate statistical analyses. The use of serum‐plasma matched samples afforded a broad‐scope detection of 1,570 metabolic features. Metabolic phenotypes revealed significant pattern differences for healthy versus BTN and healthy versus PTC. Perturbed metabolic pathways related mainly to amino acid and lipid metabolism. It is worth noting that, BTN and PTC showed no significant differences but rather overlap in circulating metabolic signatures, and this observation was replicated in all study centers. For differential diagnosis of healthy versus thyroid nodules (BTN + PTC), a panel of 6 metabolic markers, namely myo‐inositol, α‐N‐phenylacetyl‐L‐glutamine, proline betaine, L‐glutamic acid, LysoPC(18:0) and LysoPC(18:1) provided area under the curve of 97.68% in the discovery phase and predictive accuracies of 84.78–98.18% in the 4 validation centers. Taken together, serum‐plasma matched metabolomics showed significant differences in circulating metabolites for healthy versus nodules but not for BTN versus PTC. Our results highlight the true metabolic nature of thyroid nodules, and potentially decrease overtreatment that exposes patients to unnecessary risks.
What's new?
When thyroid nodules are classified “indeterminate,” is it better to wait and see, or take out the thyroid? Usually, doctors remove the thyroid, resulting in a lifetime of levothyroxine replacement, yet most often the nodules are not cancerous. Here, the authors investigated whether metabolic profile could give a more accurate prediction of whether a thyroid nodule is cancerous. They tested healthy patients, those with benign nodules, and those with papillary thyroid carcinoma. Healthy patients showed distinct differences from those with benign nodules and those with carcinomas, while significant overlap was observed between circulating metabolites from BTN and PTC patients.
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