过氧化氢预处理增强敏感型黑豆抗铝能力的生理机制

以铝敏感型黑豆(简称SB)幼苗为实验材料,在水培条件下进行不同浓度过氧化氢(H2O2)和AlCl3处理,考察其生长和相关生理指标变化,探讨H2 O2预处理缓解黑豆铝毒害的生理以及分子机理.结果显示:(1)黑豆幼苗根的相对生长量在0.1和1.0 μmol·L-1 H2O2处理下始终得到显著促进,并以后者效果更好,而在10.0和100.0 μmol·L1 H2O2处理下先表现促进后受到显著抑制.(2)经过1.0 μmol·L-1 H2O2预处理的SB幼苗在不同程度Al3+胁迫(50～400 μmol·L 1)3周后,其叶片和根中总蛋白含量分别显著增加了16.7％～41.2％和10.0％～25.0％,MDA含量减少了近50％;而其同期的SOD和POD活性显著增加.(3) H2 O2预处理可诱导SB根和叶中的SOD基因(Mg/Fe-SOD和Mn-SOD)的表达水平明显提高.研究表明,低浓度H2O2能显著促进铝胁迫下铝敏感型黑豆幼苗生长,且主要是通过增加植株抗氧化酶活性和相关基因表达水平来提高其对铝胁迫的抗性.     

Metabolic stability and inhibitory effect of O-methylated theaflavins on H2O2-induced oxidative damage in human HepG2 cells

Seven new O-methylated theaflavins (TFs) were synthesized by using O-methyltransferase from an edible mushroom. Using TFs and O-methylated TFs, metabolic stability in pooled human liver S9 fractions and inhibitory effect on H₂O₂-induced oxidative damage in human HepG2 cells were investigated. In O-methylation of theaflavin 3′-O-gallate (TF3′G), metabolic stability was potentiated by an increase in the number of introduced methyl groups. O-methylation of TF3,3′G did not affect metabolic stability, which was likely because of a remaining 3-O-galloyl group. The inhibitory effect on oxidative damage was assessed by measuring the viability of H₂O₂-damaged HepG2 cells treated with TFs and O-methylated TFs. TF3,3′G and O-methylated TFs increased cell viabilities significantly compared with DMSO, which was the compound vehicle (p?<?0.05), and improved to approximately 100%. Only TF3′G did not significantly increase cell viability. It was suggested that the inhibitory effect on H₂O₂-induced oxidative damage was potentiated by O-methylation or O-galloylation of TFs.     

A hierarchical nest survival model integrating incomplete temporally varying covariates

Nest success is a critical determinant of the dynamics of avian populations, and nest survival modeling has played a key role in advancing avian ecology and management. Beginning with the development of daily nest survival models, and proceeding through subsequent extensions, the capacity for modeling the effects of hypothesized factors on nest survival has expanded greatly. We extend nest survival models further by introducing an approach to deal with incompletely observed, temporally varying covariates using a hierarchical model. Hierarchical modeling offers a way to separate process and observational components of demographic models to obtain estimates of the parameters of primary interest, and to evaluate structural effects of ecological and management interest. We built a hierarchical model for daily nest survival to analyze nest data from reintroduced whooping cranes (Grus americana) in the Eastern Migratory Population. This reintroduction effort has been beset by poor reproduction, apparently due primarily to nest abandonment by breeding birds. We used the model to assess support for the hypothesis that nest abandonment is caused by harassment from biting insects. We obtained indices of blood‐feeding insect populations based on the spatially interpolated counts of insects captured in carbon dioxide traps. However, insect trapping was not conducted daily, and so we had incomplete information on a temporally variable covariate of interest. We therefore supplemented our nest survival model with a parallel model for estimating the values of the missing insect covariates. We used Bayesian model selection to identify the best predictors of daily nest survival. Our results suggest that the black fly Simulium annulus may be negatively affecting nest survival of reintroduced whooping cranes, with decreasing nest survival as abundance of S. annulus increases. The modeling framework we have developed will be applied in the future to a larger data set to evaluate the biting‐insect hypothesis and other hypotheses for nesting failure in this reintroduced population; resulting inferences will support ongoing efforts to manage this population via an adaptive management approach. Wider application of our approach offers promise for modeling the effects of other temporally varying, but imperfectly observed covariates on nest survival, including the possibility of modeling temporally varying covariates collected from incubating adults.     

Dealing with paralogy in RADseq data: in silico detection and single nucleotide polymorphism validation in Robinia pseudoacacia L.

The RADseq technology allows researchers to efficiently develop thousands of polymorphic loci across multiple individuals with little or no prior information on the genome. However, many questions remain about the biases inherent to this technology. Notably, sequence misalignments arising from paralogy may affect the development of single nucleotide polymorphism (SNP) markers and the estimation of genetic diversity. We evaluated the impact of putative paralog loci on genetic diversity estimation during the development of SNPs from a RADseq dataset for the nonmodel tree species Robinia pseudoacacia L. We sequenced nine genotypes and analyzed the frequency of putative paralogous RAD loci as a function of both the depth of coverage and the mismatch threshold allowed between loci. Putative paralogy was detected in a very variable number of loci, from 1% to more than 20%, with the depth of coverage having a major influence on the result. Putative paralogy artificially increased the observed degree of polymorphism and resulting estimates of diversity. The choice of the depth of coverage also affected diversity estimation and SNP validation: A low threshold decreased the chances of detecting minor alleles while a high threshold increased allelic dropout. SNP validation was better for the low threshold (4×) than for the high threshold (18×) we tested. Using the strategy developed here, we were able to validate more than 80% of the SNPs tested by means of individual genotyping, resulting in a readily usable set of 330 SNPs, suitable for use in population genetics applications.     

Differential foraging success across a light level spectrum explains the maintenance and spatial structure of colour morphs in a polymorphic bird

Detectability of different colour morphs under varying light conditions has been proposed as an important driver in the maintenance of colour polymorphism via disruptive selection. To date, no studies have tested whether different morphs have selective advantages under differing light conditions. We tested this hypothesis in the black sparrowhawk, a polymorphic raptor exhibiting a discrete white and dark morph, and found that prey provisioning rates differ between the morphs depending on light condition. Dark morphs delivered more prey in lower light conditions, while white morphs provided more prey in brighter conditions. We found support for the role of breeding season light level in explaining the clinal pattern of variation in morph ratio across the species range throughout South Africa. Our results provide the first empirical evidence supporting the hypothesis that polymorphism in a species, and the spatial structuring of morphs across its distribution, may be driven by differential selective advantage via improved crypsis, under varying light conditions.     

Isolation and Identification of Pathogens Causing Marigold (Tagetes erecta L.) Black Spot in Beijing,China

Black spot leads to great marigold losses worldwide. The disease is characterized by black spots on leaves and stems in its early stages, and the whole plant has black rot at the advanced stage. In this report, 6 of 217 Alternaria strains isolated from lesions of marigold plants in Beijing were randomly selected. The morphological characteristics and a pathogenic tree based on two protein‐coding genes (gpd and alt a 1) indicated that Alternaria tagetica is the causal agent of marigold black spot in Beijing. All six Alternaria strains could successfully re‐infect marigold, but they could not infect carrot or zinnia by either spore spray in a greenhouse or planting experiments in the epidemic area. This is the first report of the A. tagetica pathogen being isolated from marigold in Beijing.     

First Report of Black Leaf Spot Caused by Alternaria alternata on Ramie in China

In 2012 and 2013, black leaf spot disease was observed on ramie plants in Hunan and Hubei Provinces, China. In the field, the symptoms of this disease included dark green to black big spots on leaves, often resulting in upwardly curled leaf margins. The pathogen isolates were identified as Alternaria alternata (Fr.) Keissler on the basis of morphology and sequence similarity of 99–100% to the published data for internal transcribed spacer (ITS), and glyceraldehyde‐3‐phosphate dehydrogenase (gdp). To our knowledge, this is the first report of Alternaria leaf spot of ramie in China.     

Suppressing Interfacial Dipoles to Minimize Open‐Circuit Voltage Loss in Quantum Dot Photovoltaics

Quantum‐dot (QD) photovoltaics (PVs) offer promise as energy‐conversion devices; however, their open‐circuit‐voltage (V_OC) deficit is excessively large. Previous work has identified factors related to the QD active layer that contribute to V_OC loss, including sub‐bandgap trap states and polydispersity in QD films. This work focuses instead on layer interfaces, and reveals a critical source of V_OC loss: electron leakage at the QD/hole‐transport layer (HTL) interface. Although large‐bandgap organic materials in HTL are potentially suited to minimizing leakage current, dipoles that form at an organic/metal interface impede control over optimal band alignments. To overcome the challenge, a bilayer HTL configuration, which consists of semiconducting alpha‐sexithiophene (α‐6T) and metallic poly(3,4‐ethylenedioxythiphene) polystyrene sulfonate (PEDOT:PSS), is introduced. The introduction of the PEDOT:PSS layer between α‐6T and Au electrode suppresses the formation of undesired interfacial dipoles and a Schottky barrier for holes, and the bilayer HTL provides a high electron barrier of 1.35 eV. Using bilayer HTLs enhances the V_OC by 74 mV without compromising the J_SC compared to conventional MoO₃ control devices, leading to a best power conversion efficiency of 9.2% (>40% improvement relative to relevant controls). Wider applicability of the bilayer strategy is demonstrated by a similar structure based on shallow lowest‐unoccupied‐molecular‐orbital (LUMO) levels.     

In vitro protein digestion kinetics of protein sources for pigs

In current feed evaluation systems, the nutritional value of protein sources in diets for pigs is based on the ileal digestibility of protein and amino acids, which does not account for the kinetics of protein digestion along the gastrointestinal tract. The objective of the present study was to determine the in vitro protein digestion kinetics of different protein sources (soya bean meal (SBM), wheat gluten (WG), rapeseed meal (RSM), whey powder (WP), dried porcine plasma protein, yellow meal worm larvae and black soldier fly larvae (BSF)). Protein sources were incubated with pepsin at pH 3.5 for 0 to 90 min and subsequently with pancreatin at pH 6.8 for 0 to 210 min at 39°C. The in vitro protein digestion kinetics were described as the kinetics of nitrogen (N) solubilisation and the release of low molecular weight peptides (LMW) (<500 Da). The N solubilisation rate ranged from 0.025 min⁻¹ for BSF to 0.685 min⁻¹ for WP during the incubation with pepsin, and from 0.027 min⁻¹ for RSM to 0.343 min⁻¹ for WP during the incubation with pancreatin. The release rate of LMW peptides ranged from 0.027 min⁻¹ for WG to 0.093 min⁻¹ for WP during the incubation with pepsin, and from 0.029 min⁻¹ for SBM to 0.385 min⁻¹ for WP. Black soldier fly larvae showed a similar release rate of LMW peptides as WP during the incubation with pancreatin. At the end of the sequential incubation with pepsin (90 min) and pancreatin (210 min), WG and WP showed the highest percentage of N present in LMW peptides relative to total N (78% and 79%, respectively), whereas SBM showed the lowest (35%). In conclusion, protein sources for pig diets show substantial differences in in vitro protein digestion kinetics as measured by the kinetics of N solubilisation and the release of LMW peptides. The rate of release of LMW peptides was not correlated to the rate of N solubilisation for each of the protein sources evaluated.