基于稀疏编码和SCG BPNN的鳞翅目昆虫图像识别

【目的】为了给林业、 农业或植物检疫等行业人员提供一种方便快捷的昆虫种类识别方法, 本文提出了一种新颖的鳞翅目昆虫图像自动识别方法。【方法】首先通过预处理对采集的昆虫标本图像去除背景, 分割出双翅, 并对翅图像的位置进行校正。然后把校正后的翅面分割成多个超像素, 用每个超像素的l, a, b颜色及x, y坐标平均值作为其特征数据。接下来用稀疏编码(SC)算法训练码本、 生成编码并汇集成特征向量训练量化共轭梯度反向传播神经网络（SCG BPNN）, 并用得到的BPNN进行分类识别。【结果】该方法对包含576个样本的昆虫图像的数据库进行了测试, 取得了高于99%的识别正确率, 并有理想的时间性能、 鲁棒性及稳定性。【结论】实验结果证明了本文方法在识别鳞翅目昆虫图像上的有效性。     

Sulforaphene enhances radiosensitivity of hepatocellular carcinoma through suppression of the NF‐κB pathway

Sulforaphene (SFE), a naturally occurring isothiocyanate found in cruciferous vegetables, has attracted increasing attention for its anti‐cancer effect in many cancers, including hepatocellular carcinoma (HCC). However, the precise role of SFE in the radiosensitivity of HCC is still unclear. Here, cell proliferation and apoptosis were detected by MTT and flow cytometry assay, respectively. The activity of NF‐κB was further evaluated by ELISA. We also observed the effect of SFE and/or radiation on tumor growth. The results showed that SFE inhibited cell proliferation and induced apoptosis in HCC cells. Radiation increased NF‐kB activity, while PDTC, a NF‐kB inhibitor, enhanced radiation‐induced cell death. SFE inhibited NF‐kB activity and the downstream gene expressions of the NF‐kB pathway in HCC cells. Moreover, SFE enhanced the inhibitory effect of radiation on tumor growth both in vitro and in vivo. This study indicated that SFE sensitized the radiosensitivity of HCC by blocking the NF‐kB pathway.     

Long non‐coding RNA H19 promotes the proliferation and invasion of breast cancer through upregulating DNMT1 expression by sponging miR‐152

Long non‐coding RNA (lncRNA) H19 in tumors played important roles in various biological processes. However, the biological role and molecular mechanism of H19 in breast cancer are unclear. Here, we found that H19 was aberrantly upregulated in human breast tumor tissues and cells. A negative correlation between H19 and miR‐152 and positive correlation between H19 and DNMT1 mRNA were observed. Downregulation of H19 and DNMT1 significantly retarded breast cancer cell proliferation and invasion. H19 act as an endogenous sponge by directly binding to miR‐152. miR‐152 directly targeted DNMT1 and was regulated by H19. Besides, H19 overexpression dramatically relieved the inhibition of miR‐152 on DNMT1 expression. miR‐152 inhibition and DNMT1 overexpression obviously reversed the inhibitory effects of H19 downregulation on cell proliferation and invasion. In conclusion, H19 promoted proliferation and invasion of breast cancer through the miR‐152/DNMT1 axis, providing a novel mechanism about the occurrence and development of breast cancer.     

靶向抑制铜伴侣蛋白CCS逆转卵巢癌C13*细胞的顺铂耐药性

顺铂（cisplatin）,即二胺二氯铂/diaminedichloroplatinum（DDP）,是治疗卵巢癌最有效的化疗药物;然而,耐药性是限制顺铂临床治疗效果的最重要因素。目前,卵巢癌对顺铂的耐药机制仍不十分清楚。超氧化物歧化酶1铜伴侣蛋白（copper chaperone for superoxide dismutase 1, CCS）介导Cu2+特异性传递给超氧化物歧化酶1（superoxide dismutase1, SOD1）,为维持细胞增殖和生存所必需;相反,抑制CCS可减缓肿瘤细胞增殖。本研究旨在证明,AMPK依赖的CCS表达与卵巢癌的顺铂耐药有关。实时定量PCR及免疫印迹结果显示,与顺铂敏感细胞株OV2008比较,顺铂耐药细胞株C13*中的CCS mRNA和蛋白质表达水平明显上调。shRNA靶向沉默CCS或采用抑制剂DC_AC50抑制CCS后,可明显增强顺铂对C13*细胞增殖的抑制作用,提示CCS高表达与顺铂耐药相关,而抑制CCS可逆转顺铂的耐药性。同样,免疫印迹结果证明,CCS在A549、H1944等6种不同肺癌细胞中的表达水平高低与顺铂敏感性密切相关。采用siRNA干扰CCS在A549细胞中的高表达,或在CCS低表达的H1944细胞中过表达CCS,可明显增加A549或减弱H1944细胞对顺铂的敏感性,进一步证明CCS表达与顺铂耐药性相关。此外,采用AMPK抑制剂化合物C阻断AMPKα Thr172磷酸化（激活）,即抑制AMPK信号通路,可明显抑制CCS在C13*细胞中的表达,提高其对顺铂的敏感性。以上研究结果提示,AMPK信号通路依赖的CCS表达参与肿瘤的顺铂耐药机制,而抑制CCS逆转顺铂耐药。本文的结果还提示,CCS有望成为克服顺铂耐药的潜在靶点。     

Involvement of Nox2 and Nox4 NADPH oxidases in early brain injury after subarachnoid hemorrhage

Oxidative stress is responsible for a poor prognosis of subarachnoid hemorrhage (SAH) patients. Nox2 has been shown to participate in SAH-induced early brain injury (EBI). Nox4 is another major subtype of Nox family widely expressed in central nervous system (CNS). Here, we investigated the role of Nox4 and whether there was a synergistic effect of Nox2 and Nox4 in SAH-induced EBI. Clinical brain biopsies of four patients with traumatic brain injury (TBI) and perihematomal brain tissue from six subjects with SAH were examined. Gp91ds-tat (a specific inhibitor of Nox2), GKT137831 (a specific inhibitor of Nox4), and apocynin (a non-specific Nox inhibitor) were used to test the role of Nox2 and Nox4. The protein levels of Nox2 and Nox4 were elevated in rat neurons and astrocytes at 12?h after SAH, and in cultured brain microvascular endothelial cells at 24?h after exposure to OxyHb. Similarly, there were higher Nox2 and Nox4 protein levels in perihematomal neurons and astrocytes in SAH patients than that in brain tissue from subjects with TBI. In SAH rat model, gp91ds-tat and GKT137831 could reduce SAH-induced neuronal death and degeneration, whereas apocynin did not induce a more intense neuroprotection. Consistently, in in vitro SAH model, siRNA-mediated silencing of Nox2 and Nox4 suppressed the OxyHb-induced neuronal apoptosis, whereas Nox2 and Nox4 co-knockdown also did not show a remarkable overlay effect. In conclusion, Nox4 should contribute to the pathological processes in SAH-induced EBI, and there was not an overlay effect of Nox2 inhibition and Nox4 inhibition on preventing SAH-induced EBI.     

The Life Cycle of Didymium laxifilum and Physarum album on Oat Agar Culture

The plasmodial slime molds is the largest group in the phylum Amoebozoa. Its life cycle includes the plasmodial trophic stage and the spore‐bearing fruiting bodies. However, only a few species have their complete life cycle known in details so far. This study is the first reporting the morphogenesis of Didymium laxifilum and Physarum album. Spores, from field‐collected sporangia, were incubated into hanging drop cultures for viewing germination and axenic oat agar plates for viewing plasmodial development and sporulation. The spores of D. laxifilum and P. album germinated by method of V‐shape split and minute pore, respectively. The amoeboflagellates, released from spores, were observed in water film. The phaneroplasmodia of two species developed into a number of sporangia by subhypothallic type on oat agar culture. The main interspecific difference of morphogenesis was also discussed.     

Structural basis of NF-κB signaling by the p75 neurotrophin receptor interaction with adaptor protein TRADD through their respective death domains

The p75 neurotrophin receptor (p75^NTR) is a critical mediator of neuronal death and tissue remodeling and has been implicated in various neurodegenerative diseases and cancers. The death domain (DD) of p75^NTR is an intracellular signaling hub and has been shown to interact with diverse adaptor proteins. In breast cancer cells, binding of the adaptor protein TRADD to p75^NTR depends on nerve growth factor and promotes cell survival. However, the structural mechanism and functional significance of TRADD recruitment in neuronal p75^NTR signaling remain poorly understood. Here we report an NMR structure of the p75^NTR-DD and TRADD-DD complex and reveal the mechanism of specific recognition of the TRADD-DD by the p75^NTR-DD mainly through electrostatic interactions. Furthermore, we identified spatiotemporal overlap of p75^NTR and TRADD expression in developing cerebellar granule neurons (CGNs) at early postnatal stages and discover the physiological relevance of the interaction between TRADD and p75^NTR in the regulation of canonical NF-κB signaling and cell survival in CGNs. Our results provide a new structural framework for understanding how the recruitment of TRADD to p75^NTR through DD interactions creates a membrane-proximal platform, which can be efficiently regulated by various neurotrophic factors through extracellular domains of p75^NTR, to propagate downstream signaling in developing neurons.     

Arbuscular mycorrhizal fungi affect seedling recruitment: a potential mechanism by which N deposition favors the dominance of grasses over forbs

Background and aims

Nitrogen (N) deposition usually alters plant community structure and reduces plant biodiversity in grasslands. Seedling recruitment is essential for maintaining species richness and determines plant community composition. Arbuscular mycorrhizal fungi (AMF) are widespread symbiotic fungi and could facilitate seedling establishment. Here we conducted an experiment to address whether the influence of AMF on seedling recruitment depends on N addition and plant species.

Methods

Leymus chinensis were cultivated for 5 months in the microcosms that were inoculated with or without AMF at five N addition rates. Seeds of three main species (two C₃ grasses and one non-N₂-fixing forb) of the Eurasian steppe were sown to the 5-month-old microcosms. Seedling establishment was estimated by shoot biomass, N and P contents 7 weeks after seedling germination.

Results

AMF promoted seedlings recruitment of two C₃ grasses at addition rates above 0.5 g N m^?2. In contrast, seedling recruitment of the non-N₂-fixing forb was increased by AMF at addition rates below 0.5 g N m^?2 but was decreased above 2.5 g N m^?2.

Conclusions

These results partly explain why N addition favored the dominance of grasses over forbs in perennial grassland communities. Our study indicates that AMF have the potential to influence plant community composition by mediating revegetation in the face of N deposition.     

Metabolic Flux Analysis of Plastidic Isoprenoid Biosynthesis in Poplar Leaves Emitting and Nonemitting Isoprene

The plastidic 2-C-methyl-d-erythritol-4-phosphate (MEP) pathway is one of the most important pathways in plants and produces a large variety of essential isoprenoids. Its regulation, however, is still not well understood. Using the stable isotope ¹³C-labeling technique, we analyzed the carbon fluxes through the MEP pathway and into the major plastidic isoprenoid products in isoprene-emitting and transgenic isoprene-nonemitting (NE) gray poplar (Populus × canescens). We assessed the dependence on temperature, light intensity, and atmospheric [CO₂]. Isoprene biosynthesis was by far (99%) the main carbon sink of MEP pathway intermediates in mature gray poplar leaves, and its production required severalfold higher carbon fluxes compared with NE leaves with almost zero isoprene emission. To compensate for the much lower demand for carbon, NE leaves drastically reduced the overall carbon flux within the MEP pathway. Feedback inhibition of 1-deoxy-d-xylulose-5-phosphate synthase activity by accumulated plastidic dimethylallyl diphosphate almost completely explained this reduction in carbon flux. Our data demonstrate that short-term biochemical feedback regulation of 1-deoxy-d-xylulose-5-phosphate synthase activity by plastidic dimethylallyl diphosphate is an important regulatory mechanism of the MEP pathway. Despite being relieved from the large carbon demand of isoprene biosynthesis, NE plants redirected only approximately 0.5% of this saved carbon toward essential nonvolatile isoprenoids, i.e. β-carotene and lutein, most probably to compensate for the absence of isoprene and its antioxidant properties.Isoprenoids represent the largest and most diverse group (over 50,000) of natural compounds and are essential in all living organisms (Gershenzon and Dudareva, 2007; Thulasiram et al., 2007). They are economically important for humans as flavor and fragrance, cosmetics, drugs, polymers for rubber, and precursors for the chemical industry (Chang and Keasling, 2006). The broad variety of isoprenoid products is formed from two building blocks, dimethylallyl diphosphate (DMADP) and isopentenyl diphosphate (IDP). In plants, the plastidic 2-C-methyl-d-erythritol-4-phosphate (MEP) pathway (Zeidler et al., 1997) produces physiologically and ecologically important volatile organic compounds (VOCs), the carotenoids (tetraterpenes; Giuliano et al., 2008; Cazzonelli and Pogson, 2010), diterpenes, the prenyl side-chains of chlorophylls (Chls) and plastoquinones, isoprenylated proteins, the phytohormones gibberellins, and side-chain of cytokinins (for review, see Dudareva et al., 2013; Moses et al., 2013). Industrially important prokaryotes (e.g. Escherichia coli) also use the MEP pathway for the biosynthesis of isoprenoids (Vranová et al., 2012), and there is an increasing interest in manipulating the MEP pathway of engineered microbes to increase production of economically relevant isoprenoids (Chang and Keasling, 2006). To achieve this, a mechanistic understanding of the regulation of the MEP pathway is needed (Vranová et al., 2012).Some plants, including poplars (Populus spp.), produce large amounts of the hemiterpene VOC isoprene. Worldwide isoprene emissions from plants are estimated to be 600 teragrams per year and to account for one-third of all hydrocarbons emitted to the atmosphere (Arneth et al., 2008; Guenther, 2013). Isoprene has strong effects on air chemistry and climate by participating in ozone formation reactions (Fuentes et al., 2000), by prolonging the lifespan of methane, a greenhouse gas (Poisson et al., 2000; Archibald et al., 2011), and by taking part in the formation of secondary organic aerosols (Kiendler-Scharr et al., 2012).Poplar leaves invest a significant amount of recently fixed carbon in isoprene biosynthesis (Delwiche and Sharkey, 1993; Schnitzler et al., 2010; Ghirardo et al., 2011) to cope with abiotic stresses (Sharkey, 1995; Velikova and Loreto, 2005; Behnke et al., 2007, 2010b, 2013; Vickers et al., 2009; Loreto and Schnitzler, 2010; Sun et al., 2013b), although there are indications that other protective mechanisms can partially compensate the lack of isoprene emission in genetically transformed poplars (Behnke et al., 2012; Way et al., 2013). It has been suggested that in isoprene-emitting (IE) species, most of the carbon that passes through the MEP pathway is used for isoprene biosynthesis (Sharkey and Yeh, 2001). However, a recent study using pulse-chase labeling with ¹⁴C has shown continuous synthesis and degradation of carotenes and Chl a in mature leaves of Arabidopsis (Arabidopsis thaliana; Beisel et al., 2010), and the amount of flux diverted to carotenoid and Chl synthesis compared with isoprene biosynthesis in poplar leaves is not known.Isoprene emission is temperature, light, and CO₂ dependent (Schnitzler et al., 2005; Rasulov et al., 2010; Way et al., 2011; Monson et al., 2012; Li and Sharkey, 2013a). It has been demonstrated that isoprene biosynthesis depends on the activities of IDP isomerase (EC 5.3.3.2), isoprene synthase (ISPS; EC 4.2.3.27), and the amount of ISPS substrate, DMADP (Brüggemann and Schnitzler, 2002a, 2002b; Schnitzler et al., 2005; Rasulov et al., 2009b). In turn, DMADP concentration has been hypothesized to act as a feedback regulator of the MEP pathway by inhibiting 1-deoxy-d-xylulose-5-phosphate synthase (DXS; EC 2.2.1.7), the first enzyme of the MEP pathway (Banerjee et al., 2013). Understanding the controlling mechanism of isoprene biosynthesis is not only of fundamental relevance, but also necessary for engineering the MEP pathway in various organisms and for accurate simulation of isoprene emissions by plants in predicting atmospheric reactivity (Niinemets and Monson, 2013).There is ample evidence that silencing the ISPS in poplar has a broad effect on the leaf metabolome (Behnke et al., 2009, 2010a, 2013; Way et al., 2011; Kaling et al., 2014). While some of those changes (e.g. ascorbate and α-tocopherol) are compensatory mechanisms to cope with abiotic stresses, others (e.g. shikimate pathway and phenolic compounds) might be related to the alteration of the MEP pathway (Way et al., 2013; Kaling et al., 2014). The perturbation of these metabolic pathways can be attributed to the removal of a major carbon sink of the MEP pathway and the resulting change in the energy balance within the plant cell (Niinemets et al., 1999; Ghirardo et al., 2011). In this work, we analyzed the carbon fluxes through the MEP pathway into the main plastidic isoprenoid products.We used the ¹³C-labeling technique as a tool to measure the carbon fluxes through the MEP pathway at different temperatures, light intensities, and CO₂ concentrations in mature leaves of IE and transgenic, isoprene-nonemitting (NE) gray poplar (Populus × canescens). Isoprene emission was drastically reduced in the transgenic trees through knockdown of PcISPS gene expression by RNA interference, resulting in plants with only 1% to 5% of isoprene emission potential compared with wild-type plants (Behnke et al., 2007).We measured the appearance of ¹³C in the isoprenoid precursors 2-C-methyl-d-erythritol-2,4-cyclodiphosphate (MEcDP) and DMADP as well as isoprene and the major downstream products of the MEP pathway, i.e. carotenoids and Chls. To reliably detect de novo synthesis of the pigments, which occur at very low rates (Beisel et al., 2010), we used isotope ratio mass spectrometry (IRMS).Here, (1) we quantify the effect of isoprene biosynthesis on the MEP pathway in poplar, and (2) we show that suppression of isoprene biosynthesis negatively affects the carbon flux through the MEP pathway by accumulating plastidic DMADP, which feeds back to inhibit PcDXS, leading to (3) a slight increase of carbon flux toward production of greater chain-length isoprenoids and (4) a strong decrease in the overall isoprenoid carbon fluxes to compensate for the much lower MEP pathway demand for carbon. This study strongly supports the hypothesis that an important regulatory mechanism of the MEP pathway is the feedback regulation of plastidic DMADP on DXS. The large carbon flux through the MEP pathway of IE poplar plastids demonstrates the potential of transgenically altered IE plant species to produce economically valuable isoprenoids at high rates in, for instance, industrial applications.