Chromatin remodeler Dmp18 regulates apoptosis by controlling H2Av incorporation in Drosophila imaginal disc development.

Programmed Cell Death (PCD) or apoptosis is a highly conserved biological process and plays essential roles both in the development and stress context. In Drosophila, expression of pro-apoptotic genes, including reaper (rpr), head involution defective (hid), grim, and sickle (skl), is sufficient to induce cell death. Here, we demonstrate that the chromatin remodeler Dmp18, the homolog of mammalian Znhit1, plays a crucial role in regulating apoptosis in eye and wing development. We showed that loss of Dmp18 disrupted eye and wing development, up-regulated transcription of pro-apoptotic genes, and induced apoptosis. Inhibition of apoptosis suppressed the eye defects caused by Dmp18 deletion. Furthermore, loss of Dmp18 disrupted H2Av incorporation into chromatin, promoted H3K4me3, but reduced H3K27me3 modifications on the TSS regions of pro-apoptotic genes. These results indicate that Dmp18 negatively regulates apoptosis by mediating H2Av incorporation and histone H3 modifications at pro-apoptotic gene loci for transcriptional regulation. Our study uncovers the role of Dmp18 in regulating apoptosis in Drosophila eye and wing development and provides insights into chromatin remodeling regulating apoptosis at the epigenetic levels.

Multifunctional nano-in-micro delivery systems for targeted therapy in fundus neovascularization diseases.

Fundus neovascularization diseases are a series of blinding eye diseases that seriously impair vision worldwide. Currently, the means of treating these diseases in clinical practice are continuously evolving and have rapidly revolutionized treatment opinions. However, key issues such as inadequate treatment effectiveness, high rates of recurrence, and poor patient compliance still need to be urgently addressed. Multifunctional nanomedicine can specifically respond to both endogenous and exogenous microenvironments, effectively deliver drugs to specific targets and participate in activities such as biological imaging and the detection of small molecules. Nano-in-micro (NIM) delivery systems such as metal, metal oxide and up-conversion nanoparticles (NPs), quantum dots, and carbon materials, have shown certain advantages in overcoming the presence of physiological barriers within the eyeball and are widely used in the treatment of ophthalmic diseases. Few studies, however, have evaluated the efficacy of NIM delivery systems in treating fundus neovascular diseases (FNDs). The present study describes the main clinical treatment strategies and the adverse events associated with the treatment of FNDs with NIM delivery systems and summarizes the anatomical obstacles that must be overcome. In this review, we wish to highlight the principle of intraocular microenvironment normalization, aiming to provide a more rational approach for designing new NIM delivery systems to treat specific FNDs.

MMP9-Responsive Graphene Oxide Quantum Dot-Based Nano-in-Micro Drug Delivery System for Combinatorial Therapy of Choroidal Neovascularization.

Age-related macular degeneration (AMD), especially wet AMD with choroidal neovascularization (CNV), commonly causes blindness in older patients and disruption of the choroid followed by second-wave injuries, including chronic inflammation, oxidative stress, and excessive matrix metalloproteinase 9 (MMP9) expression. Increased macrophage infiltrate in parallel with microglial activation and MMP9 overexpression on CNV lesions is shown to contribute to the inflammatory process and then enhance pathological ocular angiogenesis. Graphene oxide quantum dots (GOQDs), as natural antioxidants, exert anti-inflammatory effects and minocycline is a specific macrophage/microglial inhibitor that can suppress both macrophage/microglial activation and MMP9 activity. Herein, an MMP9-responsive GOQD-based minocycline-loaded nano-in-micro drug delivery system (C18PGM) is developed by chemically bonding GOQDs to an octadecyl-modified peptide sequence (C18-GVFHQTVS, C18P) that can be specifically cleaved by MMP9. Using a laser-induced CNV mouse model, the prepared C18PGM shows significant MMP9 inhibitory activity and anti-inflammatory action followed by antiangiogenic effects. Moreover, C18PGM combined with antivascular endothelial growth factor antibody bevacizumab markedly increases the antiangiogenesis effect by interfering with the "inflammation-MMP9-angiogenesis" cascade. The prepared C18PGM shows a good safety profile and no obvious ophthalmic or systemic side effects. The results taken together suggest that C18PGM is an effective and novel strategy for combinatorial therapy of CNV.

Palmitoyl transferases act as novel drug targets for pancreatic cancer.

BACKGROUND: Pancreatic adenocarcinoma (PAAD) is one of the most leading causes of cancer-related death across the world with the limited efficiency and response rate of immunotherapy. Protein S-palmitoylation, a powerful post-translational lipid modification, is well-known to regulate the stability and cellular distribution of cancer-related proteins, which is mediated by a family of 23 palmitoyl transferases, namely zinc finger Asp-His-His-Cys-type (ZDHHC). However, whether palmitoyl transferases can determine tumor progression and the efficacy of immunotherapy in PAAD remains unknown. METHODS: Bioinformatics methods were used to identify differential ZDHHCs expression in PAAD. A systematic pan-cancer analysis was conducted to assess the immunological role of ZDHHC3 using RNA sequencing data from The Cancer Genome Atlas database. In vivo Panc 02 subcutaneous tumor model validated the anti-tumor effect of knockdown of ZDHHC3 or intraperitoneal injection of 2-bromopalmitate (2-BP), a typical broad-spectrum palmitoyl transferases inhibitor. Furthermore, we explored therapeutic strategies with combinations of 2-BP with PD-1/PD-L1-targeted immunotherapy in C57BL/6 mice bearing syngeneic Panc 02 pancreatic tumors. RESULTS: ZDHHC enzymes were associated with distinct prognostic values of pancreatic cancer. We identified that ZDHHC3 expression promotes an immunosuppressive tumor microenvironment in PAAD. 2-BP suppressed pancreatic-tumor cell viability and tumor sphere-forming activities, as well as increased cell apoptosis in vitro, without affecting normal human pancreatic ductal epithelial cells. Furthermore, genetic inactivation of ZDHHC3 or intraperitoneal injection of 2-BP impeded tumor progression in Panc 02 pancreatic tumors with enhanced anti-tumor immunity. 2-BP treatment significantly enhanced the therapeutic efficacy of PD-1/PD-L1 inhibitors in Panc 02 pancreatic tumors. CONCLUSION: This study revealed some ZDHHC enzyme genes for predicting the prognosis of pancreatic cancer, and demonstrated that ZDHHC3 plays a critical oncogenic role in pancreatic cancer progression, highlighting its potential as an immunotherapeutic target of pancreatic cancer. In addition, combination therapy of 2-BP and PD-1/PD-L1 achieved synergic therapy effects in a mouse model of pancreatic cancer.

Scale Effect of Surface Asperities on Stick-Slip Behavior of Zinc-Coated Steel.

Stick-slip behavior between friction pairs causes severe vibration problems such as abrasion and noise pollution, leading to material loss and deterioration in human health. This phenomenon is extremely complex because the surfaces of friction pairs have various asperities with different sizes. Therefore, it is of importance to understand the scale effect of asperities on the stick-slip behavior. Here, we selected four kinds of zinc-coated steels with multiscale surface asperities as a presentative example to reveal what types of asperities play the key role in affecting the stick-slip behavior. It is discovered that the stick-slip behavior is dominated by the density of small-scale asperities rather than large-scale asperities. High-density small-scale asperity increases the potential energy between asperities of the friction pairs, which leads to stick-slip behavior. It is suggested that decreasing the density of small-scale asperity on the surface significantly suppresses the stick-slip behavior. The present study reveals the scale effect of surface asperities on the stick-slip behavior and thus could offer a pathway to tailoring the surface topography of a wide range of materials for suppressing the stick-slip behavior.

Effect of Wear-Induced Surface Deformation on Stick-Slip Friction of Galvanized Automotive Steels.

This study examined the influence of worn surfaces on the stick-slip friction of galvanized automotive steel and revealed the intrinsic role of surface topography parameters in the stick-slip friction with wear. The results show that the surface deformation induced by wear significantly affects the stick-slip friction. The stick-slip friction can be suppressed by increasing the vertical area of the surface deformation because of reductions in the difference between the static and kinetic friction coefficients. The friction behavior changes from stick-slip friction to smooth sliding when the skewness exceeds a critical value, thus suggesting that this parameter can be used as an effective surface topography parameter to describe the stick-slip friction of galvanized automotive steel with worn surfaces. The findings can help improve the understanding of the mechanism of the stick-slip friction of materials with worn surfaces and provide an approach to suppress the noise and vibration caused by the stick-slip friction of galvanized automotive steel.

HAX1 maintains the glioma progression in hypoxia through promoting mitochondrial fission.

HCLS1-associated protein X-1 (HAX1), an anti-apoptotic molecular, overexpresses in glioma. However, the role of HAX1 in glioma cell surviving in hypoxic environment remains unclear. Western blotting, qRT-PCR, Transwell assay, TUNEL assay, wounding healing assay, clone formation, tumour xenograft model and immunohistochemical staining were used to investigate the role of HAX1 in glioma. HAX1 regulated by HIF-1α was increased in glioma cells cultured in hypoxia. Silencing of HAX1 could cause an increased apoptosis of glioma cells cultured in hypoxia. Silencing of HAX1 also decreased the proliferation, migration and invasion of glioma cells cultured in hypoxia. Increased mitochondrial fission could prevent glioma cells from the damage induced by HAX1 knockdown in hypoxia. Furthermore, HAX1 was found to regulate glioma cells through phosphorylated AKT/Drp signal pathway. In conclusion, our study suggested that HAX1 promoted survival of glioma cells in hypoxic environment via AKT/Drp signal pathway. Our study also provided a potential therapeutic target for glioma.

The small RNA chaperone Hfq is a critical regulator for bacterial biosynthesis of selenium nanoparticles and motility in Rahnella aquatilis.

The RNA chaperone, Hfq, is a global post-transcriptional regulator that plays an important role in regulating pleiotropic functions, such as cell growth and motility, stress tolerance, and virulence to host, in many Gram-negative bacteria. This study examined the functional roles of Hfq in Rahnella aquatilis HX2, a plant beneficial, selenium nanoparticles (SeNPs)-producing soil bacterium. A mutant HX2∆hfq with an in-frame deletion within the hfq gene in R. aquatilis HX2 was constructed and tested for various phenotypic features. Bacterial growth, motility, selenite reduction, and SeNPs production were compared between the mutant, the wild-type, and the complementation strain. The hfq gene deletion delayed the growth of strain HX2, with a lower bacterial population during the stationary phase, and significantly impaired the swimming motility of the bacterium, showing a smaller motility ring on the plate. The hfq mutation also dramatically declined microbial-induced reduction of selenite and SeNPs production in HX2, which was independent of cell growth. The introduction of a trans-expressed hfq gene into HX2∆hfq for complementation completely restored impacted phenotypes. In addition, reverse transcription real-time quantitative PCR (RT-qPCR) analysis revealed that the expression of ten genes involved in bacterial growth and survival, motility and chemotaxis, and selenite or seleno-compound metabolism were influenced by Hfq loss-of-function by at least two-fold. Six genes including two involved in SeNPs production were positively regulated by hfq, while other four genes were negatively regulated. Homolog search suggested that the rprA gene might encode a small RNA regulated by Hfq in R. aquatilis HX2. Overall, the present study provides novel information about the function of Hfq and the regulation of bacterial biosynthesis of SeNPs.

Tankyrase regulates apoptosis by activating JNK signaling in Drosophila.

Programmed cell death (PCD), or apoptosis, plays essential roles in various cellular and developmental processes, and dysregulation of apoptosis causes many diseases. Thus, regulation of apoptotic process is very important. Drosophila tankyrase (DTNKS) is an evolutionarily conserved protein with poly(ADP-ribose) polymerase activity. In mammalian cells, tankyrases (TNKSs) have been reported to regulate cell death. To determine whether DTNKS plays function in inducing apoptosis in in vivo development, we used Drosophila as a model system and generated transgenic flies expressing DTNKS. We show that ectopic expression of DTNKS promotes caspase-dependent apoptosis and knockdown of DTNKS by RNAi dramatically alleviates apoptotic defect caused by ectopic expression of pro-apoptotic protein hid or rpr in the adult eye. Moreover, our result shows that ectopic expression of DTNKS triggers the activation of c-Jun N-terminal kinase (JNK) signaling, which is required for DTNKS-mediated apoptosis. Taken together, our finding identifies the role of DTNKS in regulating apoptosis by activating JNK signaling in Drosophila.

Biosynthesis of selenium nanoparticles and effects of selenite, selenate, and selenomethionine on cell growth and morphology in Rahnella aquatilis HX2.

Rahnella aquatilis HX2 (proteobacteria) shows tolerance to selenium (Se). The minimum inhibitory concentrations of selenomethionine (Se-Met), selenite [Se (IV)], and selenate [Se (VI)] to HX2 are 4.0, 85.0, and 590.0 mM, respectively. HX2 shows the ability to reduce Se (IV) and Se (VI) to elemental Se nanoparticles (SeNPs). The maximum production of SeNPs by HX2 strain is 1.99 and 3.85 mM in Luria-Bertani (LB) broth with 5 mM Se (IV) and 10 mM Se (VI), respectively. The morphology of SeNPs and cells were observed by transmission electron microscope, environmental scanning electron microscope, and selected area electric diffraction detector. Spherical SeNPs with amorphous structure were found in the cytoplasm, membrane, and exterior of cells. Morphological variations of the cell membrane were further confirmed by the release of cellular materials absorbed at 260 nm. Flagella were inhibited and cell sizes were 1.8-, 1.6-, and 1.2-fold increases with the Se-Met, Se (VI), and Se (IV) treatments, respectively. The real-time quantitative PCR analysis indicated that some of the genes controlling Se metabolism or cell morphology, including cysA, cysP, rodA, ZntA, and ada, were significantly upregulated, while grxA, fliO, flgE, and fliC genes were significantly downregulated in those Se treatments. This study provided novel valuable information concerning the cell morphology along with biological synthesis process of SeNPs in R. aquatilis and demonstrated that the strain HX2 could be applied in both biosynthesis of SeNPs and in management of environmental Se pollution.

[Clinical features and treatment of macrolide-resistant Mycoplasma pneumoniae pneumonia in children].

OBJECTIVE: To study the clinical features of macrolide-resistant Mycoplasma pneumoniae pneumonia and its treatment regimens in children. METHODS: The samples of throat swab or bronchoalveolar lavage fluid were collected from 136 children with Mycoplasma pneumoniae pneumonia. Quantitative real-time PCR was used to detect 2063/2064 A:G mutation in 23S rRNA, and according to such results, the children were divided into drug-resistance group with 81 children and sensitive group with 55 children. The two groups were compared in terms of age composition, respiratory symptoms, extrapulmonary complications, laboratory markers, imaging changes, treatment regimens, and length of hospital stay. RESULTS: Compared with the sensitive group, the drug-resistance group had significantly longer duration of pyrexia and severe fever, a significantly higher percentage of children with reduced blood oxygen saturation, and significantly higher levels of alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) (P<0.05). The conventional azithromycin treatment had a good clinical effect in the sensitive group, while corticosteroid therapy was usually needed in the drug-resistance group. CONCLUSIONS: Macrolide-resistant Mycoplasma pneumoniae infection cannot be identified based on a single clinical feature, but prolonged duration of pyrexia and severe fever, reduced blood oxygen saturation, and increased ALT and LDH can suggest the presence of this disease. Azithromycin combined with glucocorticoids may be a good treatment regimen for children with macrolide-resistant Mycoplasma pneumoniae pneumonia.

Inhibitory effect of selenium against Penicillium expansum and its possible mechanisms of action.

Some organic and inorganic salts could inhibit the growth of many pathogens. Selenium (Se), as an essential micronutrient, was effective in improving the plant resistance and antioxidant capacity at a low concentration. Penicillium expansum is one of the most important postharvest fungal pathogens, which can cause blue mold rot in various fruits and vegetables. In this study, the inhibitory effect of Se against P. expansum was evaluated. The result showed that Se strongly inhibited spore germination, germ tube elongation, and mycelial spread of P. expansum in the culture medium. The inhibitory effect was positively related to the concentration of Se used. Fluorescence microscopy observation of P. expansum conidia stained with propidium iodide (PI) indicated that the membrane integrity decreased to 37 % after the conidia were treated with Se (20 mg/l) for 9 h. With the use of an oxidant-sensitive probe 2,7-dichlorofluorescin (DCHF-DA), we found that Se at 15 mg/l could induce the generation of intracellular reactive oxygen species (ROS). Furthermore, methane dicarboxylic aldehyde (MDA) content, hydrogen peroxide (H2O2), and superoxide anion (O2 (-)) production rate in P. expansum spores exposed to Se increased markedly. Compared with the control, the activities of superoxide dismutase (SOD) and the content of glutathione (GSH) were reduced, confirming that damage of Se to cellular oxygen-eliminating system is the main reason. These results suggest that Se might serve as a potential alternative to synthetic fungicides for the control of the postharvest disease of fruit and vegetables caused by P. expansum.

The diagnosis of arteriovenous malformations by 4D-CTA: a clinical study.

BACKGROUND AND PURPOSE: Digital subtraction angiography (DSA) is the current imaging 'gold standard' for diagnosis of arteriovenous malformation (AVM). The latest technique, four-dimensional computed tomography (4D-CT), offers a new diagnostic method for assessing AVM in real time. This study used a 320-detector-row CT scanner to compare the value of 4D-CT angiography (4D-CTA) with DSA in the diagnosis of untreated AVM patients. METHODS: Seventeen patients diagnosed with AVM by DSA were included in this study. Two independent readers blind to the results of all examinations evaluated the findings of DSA and 4D-CTA in each patient. All results were then documented using a standardized scoring sheet. RESULTS: The results of 4D-CTA in all 17 cases were fully consistent with DSA for AVM location, size and vascular structures. 4D-CTA had the same ability as DSA to distinguish the main feeding arteries in all cases, although in the identification of smaller and specific arterial branches, there were discrepancies in one patient between the two methods. In the diagnosis of draining veins, however, 4D-CTA successfully displayed all of the vessels found by DSA. CONCLUSION: 4D-CTA was able to detect all AVM lesions, including their size, location, feeding arteries and draining veins. Thus, 4D-CTA has a value similar to that of DSA in the diagnosis and assessment of AVM.

Selenium Removal from Wastewater by Microbial Transformation and Volatilization.

Selenium (Se) is a naturally occurring trace element that is nutritionally essential for humans and animals, but becomes toxic at high concentrations. This laboratory study explored the role of microbes in Se removal from contaminated wastewater via biological transformation and volatilization processes. Microbes could immobilize water-soluble selenate (SeO42-) and selenite (SeO32-) to water-insoluble elemental Se (Se0) and transform Se into volatile Se compounds found in the atmosphere. Results of this laboratory study showed that Bacillus cereus, a bacterial strain isolated from wheat straw and biosolid-WTR-sand substrates showed a significant biotransformation ability of reducing selenate and selenite to elemental Se and forming volatile Se organic compounds in wastewater. Overall, microbial Se chemical reduction, methylation, and volatilization are important processes in bioremediation of Se-contaminated wastewater.

Effects of arbuscular mycorrhizal fungi on the reduction of arsenic accumulation in plants: a meta-analysis.

Arsenic (As) accumulation in plants is a global concern. Although the application of arbuscular mycorrhizal fungi (AMF) has been suggested as a potential solution to decrease As concentration in plants, there is currently a gap in a comprehensive, quantitative assessment of the abiotic and biotic factors influencing As accumulation. A meta-analysis was performed to quantitatively investigate the findings of 76 publications on the impacts of AMF, plant properties, and soil on As accumulation in plants. Results showed a significant dose-dependent As reduction with higher mycorrhizal infection rates, leading to a 19.3% decrease in As concentration. AMF reduced As(V) by 19.4% but increased dimethylarsenic acid (DMA) by 50.8%. AMF significantly decreased grain As concentration by 34.1%. AMF also improved plant P concentration and dry biomass by 33.0% and 62.0%, respectively. The most significant reducing effects of As on AMF properties were seen in single inoculation and experiments with intermediate durations. Additionally, the benefits of AMF were significantly enhanced when soil texture, soil organic carbon (SOC), pH level, Olsen-P, and DTPA-As were sandy soil, 0.8%-1.5%, ≥7.5, ≥9.1 mg/kg, and 30-60 mg/kg, respectively. AMF increased easily extractable glomalin-related soil protein (EE-GRSP) and total glomalin-related soil protein (T-GRSP) by 23.0% and 28.0%, respectively. Overall, the investigated factors had significant implications in developing AMF-based methods for alleviating the negative effects of As stress on plants.

Self-Charging Aqueous Zn//COF Battery with UltraHigh Self-Charging Efficiency and Rate.

Self-charging zinc batteries that combine energy harvesting technology with batteries are candidates for reliable self-charging power systems. However, the lack of rational materials design results in unsatisfactory self-charging performance. Here, a covalent organic framework containing pyrene-4,5,9,10-tetraone groups (COF-PTO) is reported as a cathode material for aqueous self-charging zinc batteries. The ordered channel structure of the COF-PTO provides excellent capacity retention of 98% after 18 000 cycles at 10 A g-1 and ultra-fast ion transfer. To visually assess the self-charging performance, two parameters, namely self-charging efficiency (self-charging discharge capacity/galvanostatic discharge capacity, η) and average self-charging rate (total discharge capacity after cyclic self-charging/total cyclic self-charging time, ν), are proposed for performance evaluation. COF-PTO achieves an impressive η of 96.9% and an ν of 30 mAh g-1 self-charge capacity per hour in 100 self-charging cycles, surpassing the previous reports. Mechanism studies reveal the co-insertion of Zn2+ and H+ double ions in COF-PTO of self-charging zinc batteries. In addition, the C═N and C═O (on the benzene) in COF-PTO are ortho structures to each other, which can easily form metal heterocycles with Zn ions, thereby driving the forward progress of the self-charging reaction and enhancing the self-charging performance.

1.06 µm Q-switched ytterbium-doped fiber laser using few-layer topological insulator Bi2Se3 as a saturable absorber.

Passive Q-switching of an ytterbium-doped fiber (YDF) laser with few-layer topological insulator (TI) is, to the best of our knowledge, experimentally demonstrated for the first time. The few-layer TI: Bi2Se3 (2-4 layer thickness) is firstly fabricated by the liquid-phase exfoliation method, and has a low saturable optical intensity of 53 MW/cm² measured by the Z-scan technique. The optical deposition technique is used to induce the few-layer TI in the solution onto a fiber ferrule for successfully constructing the fiber-integrated TI-based saturable absorber (SA). By inserting this SA into the YDF laser cavity, stable Q-switching operation at 1.06 µm is achieved. The Q-switched pulses have the shortest pulse duration of 1.95 µs, the maximum pulse energy of 17.9 nJ and a tunable pulse-repetition-rate from 8.3 to 29.1 kHz. Our results indicate that the TI as a SA is also available at 1 µm waveband, revealing its potential as another broadband SA (like graphene).

Development of a constructed wetland water treatment system for selenium removal: incorporation of an algal treatment component.

On the basis of the fact that algae have the ability to volatilize substantial quantities of selenium (Se), we investigated the concept of including an algal pretreatment unit into a constructed wetland system for the removal of Se from river water entering the Salton Sea. Of six different algal strains tested, the most effective in terms of Se volatilization and Se removal from the water column was a Chlorella vulgaris strain (designated Cv). Cv removed 96% of Se (supplied as selenate) from the microcosm water column within 72 h, with up to 61% being removed by volatilization to the atmosphere. X-ray absorption spectroscopy revealed that the major forms of Se likely to be accumulated in an algal-wetland system are selenomethionine, a precursor of volatile Se formation, and elemental Se. Our results suggest that the inclusion of an algal pretreatment unit within a constructed wetland water treatment system should not only enhance the efficiency of Se removal but also significantly reduce the risk of the buildup of ecotoxic forms of Se by promoting the biological volatilization of Se.

Topographic constraints on the distribution of selenium in the supergene environment: A case study at Yutangba, China.

The local topography and leaching conditions significantly affect the spatial distribution of selenium (Se) in the local environment. However, the driving factors controlling Se distribution have not been well addressed. In this paper, taking Yutangba, a village known for human selenosis in China, as an example, we demonstrate how topographic factors influence the spatial distribution of Se in soils and plants. In the scenarios of slope ≤25°, the correlations among slope and soil/extractable/plant Se are significantly negative (P < 0.05), whereas they become weak or unclear when the slope is > 25°, suggesting that 25° of slope is a critical transition boundary. Similar observations were further verified by the soil erosion modulus (SEM) and the surface runoff intensity index (SRI), indicating that Se transport via soil erosion is limited and accounts for 11.2-17% of the soil Se, while surface runoff plays a dominant role in the Se distribution, accounting for 83-88.1%. Soil extractable Se is negatively correlated with SRI (Pearson r = -0.87 at slope < 25°), showing that the migration capacity of Se is higher at steep terrain and controlled by topography through soil erosion and surface runoff. The positive relationship between plant Se and soil/extractable Se demonstrates that topography indirectly influences plant Se through soil Se bioavailability. Abnormally local Se enrichment observed at the elevated steep hillside (>25°) in northwestern Yutangba primarily was resulted from the weathering of Se-rich rocks. These observations confirm that the topographic slope gradient influences the transport and spatial distribution of soil Se, implying that topography should be considered when studying the spatial distribution of soil Se at a regional scale, especially for the Se-poor belt in China.