Plant-Plant-Microbe Mechanisms Involved in Soil-Borne Disease Suppression on a Maize and Pepper Intercropping System

Background

Intercropping systems could increase crop diversity and avoid vulnerability to biotic stresses. Most studies have shown that intercropping can provide relief to crops against wind-dispersed pathogens. However, there was limited data on how the practice of intercropping help crops against soil-borne Phytophthora disease.

Principal Findings

Compared to pepper monoculture, a large scale intercropping study of maize grown between pepper rows reduced disease levels of the soil-borne pepper Phytophthora blight. These reduced disease levels of Phytophthora in the intercropping system were correlated with the ability of maize plants to form a “root wall” that restricted the movement of Phytophthora capsici across rows. Experimentally, it was found that maize roots attracted the zoospores of P. capsici and then inhibited their growth. When maize plants were grown in close proximity to each other, the roots produced and secreted larger quantities of 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA) and 6-methoxy-2-benzoxazolinone (MBOA). Furthermore, MBOA, benzothiazole (BZO), and 2-(methylthio)-benzothiazole (MBZO) were identified in root exudates of maize and showed antimicrobial activity against P. capsici.

Conclusions

Maize could form a “root wall” to restrict the spread of P. capsici across rows in maize and pepper intercropping systems. Antimicrobe compounds secreted by maize root were one of the factors that resulted in the inhibition of P. capsici. These results provide new insights into plant-plant-microbe mechanisms involved in intercropping systems.     

Human rhinovirus C infection is associated with asthma in children determined by xTAG respiratory viral panel FAST

<正>Dear Editor,Cumulative evidence supports the role of early-life viral infections,especially respiratory syncytial virus(RSV)and human rhinovirus(HRV),as major antecedents of childhood asthma(Lemanske,2002;Jackson et al.,2008).In this study,the x TAG respiratory viral panel FAST(RVP FAST)assay,a multiplex polymerase chain reaction(PCR)-based method(Arens et al.,2010;BaladaLlasat et al.,2011;Gharabaghi et al.,2011;Selvaraju,2012),was used to investigate the association of infec-     

Liver Ischemic Preconditioning (IPC) Improves Intestinal Microbiota Following Liver Transplantation in Rats through 16s rDNA-Based Analysis of Microbial Structure Shift

Background

Ischemia-reperfusion (I/R) injury is associated with intestinal microbial dysbiosis. The “gut-liver axis” closely links gut function and liver function in health and disease. Ischemic preconditioning (IPC) has been proven to reduce I/R injury in the surgery. This study aims to explore the effect of IPC on intestinal microbiota and to analyze characteristics of microbial structure shift following liver transplantation (LT).

Methods

The LT animal models of liver and gut IPC were established. Hepatic graft function was assessed by histology and serum ALT/AST. Intestinal barrier function was evaluated by mucosal ultrastructure, serum endotoxin, bacterial translocation, fecal sIgA content and serum TNF-α. Intestinal bacterial populations were determined by quantitative PCR. Microbial composition was characterized by DGGE and specific bacterial species were determined by sequence analysis.

Principal Findings

Liver IPC improved hepatic graft function expressed as ameliorated graft structure and reduced ALT/AST levels. After administration of liver IPC, intestinal mucosal ultrastructure improved, serum endotoxin and bacterial translocation mildly decreased, fecal sIgA content increased, and serum TNF-α decreased. Moreover, liver IPC promoted microbial restorations mainly through restoring Bifidobacterium spp., Clostridium clusters XI and Clostridium cluster XIVab on bacterial genus level. DGGE profiles indicated that liver IPC increased microbial diversity and species richness, and cluster analysis demonstrated that microbial structures were similar and clustered together between the NC group and Liver-IPC group. Furthermore, the phylogenetic tree of band sequences showed key bacteria corresponding to 10 key band classes of microbial structure shift induced by liver IPC, most of which were assigned to Bacteroidetes phylum.

Conclusion

Liver IPC cannot only improve hepatic graft function and intestinal barrier function, but also promote restorations of intestinal microbiota following LT, which may further benefit hepatic graft by positive feedback of the “gut-liver axis”.     

Multiple trade‐offs regulate the effects of woody plant removal on biodiversity and ecosystem functions in global rangelands

Woody plant encroachment is a major land management issue. Woody removal often aims to restore the original grassy ecosystem, but few studies have assessed the role of woody removal on ecosystem functions and biodiversity at global scales. We collected data from 140 global studies and evaluated how different woody plant removal methods affected biodiversity (plant and animal diversity) and ecosystem functions (plant production, hydrological function, soil carbon) across global rangelands. Our results indicate that the impact of removal is strongly context dependent, varying with the specific response variable, removal method, and traits of the target species. Over all treatments, woody plant removal increased grass biomass and total groundstorey diversity. Physical and chemical removal methods increased grass biomass and total groundstorey biomass (i.e., non‐woody plants, including grass biomass), but burning reduced animal diversity. The impact of different treatment methods declined with time since removal, particularly for total groundstorey biomass. Removing pyramid‐shaped woody plants increased total groundstorey biomass and hydrological function but reduced total groundstorey diversity. Environmental context (e.g., aridity and soil texture) indirectly controlled the effect of removal on biomass and biodiversity by influencing plant traits such as plant shape, allelopathic, or roots types. Our study demonstrates that a one‐size‐fits‐all approach to woody plant removal is not appropriate, and that consideration of woody plant identity, removal method, and environmental context is critical for optimizing removal outcomes. Applying this knowledge is fundamental for maintaining diverse and functional rangeland ecosystems as we move toward a drier and more variable climate.     

Inactivation of template-directed misfolding of infectious prion protein by ozone

Misfolded prions (PrP(Sc)) are well known for their resistance to conventional decontamination processes. The potential risk of contamination of the water environment, as a result of disposal of specified risk materials (SRM), has raised public concerns. Ozone is commonly utilized in the water industry for inactivation of microbial contaminants and was tested in this study for its ability to inactivate prions (263K hamster scrapie = PrP(Sc)). Treatment variables included initial ozone dose (7.6 to 25.7 mg/liter), contact time (5 s and 5 min), temperature (4°C and 20°C), and pH (pH 4.4, 6.0, and 8.0). Exposure of dilute suspensions of the infected 263K hamster brain homogenates (IBH) (0.01%) to ozone resulted in the in vitro destruction of the templating properties of PrP(Sc), as measured by the protein misfolding cyclic amplification (PMCA) assay. The highest levels of prion inactivation (≥4 log(10)) were observed with ozone doses of 13.0 mg/liter, at pH 4.4 and 20°C, resulting in a CT (the product of residual ozone concentration and contact time) value as low as 0.59 mg · liter(-1) min. A comparison of ozone CT requirements among various pathogens suggests that prions are more susceptible to ozone degradation than some model bacteria and protozoa and that ozone treatment may be an effective solution for inactivating prions in water and wastewater.     

Structural Insights into the Pseudomonas aeruginosa Type VI Virulence Effector Tse1 Bacteriolysis and Self-protection Mechanisms

Recently, it was identified that Pseudomonas aeruginosa competes with rival cells to gain a growth advantage using a novel mechanism that includes two interrelated processes as follows: employing type VI secretion system (T6SS) virulence effectors to lyse other bacteria, and at the same time producing specialized immunity proteins to inactivate their cognate effectors for self-protection against mutual toxicity. To explore the structural basis of these processes in the context of functional performance, the crystal structures of the T6SS virulence effector Tse1 and its complex with the corresponding immunity protein Tsi1 were determined, which, in association with mutagenesis and Biacore analyses, provided a molecular platform to resolve the relevant structural questions. The results indicated that Tse1 features a papain-like structure and conserved catalytic site with distinct substrate-binding sites to hydrolyze its murein peptide substrate. The immunity protein Tsi1 interacts with Tse1 via a unique interactive recognition mode to shield Tse1 from its physiological substrate. These findings reveal both the structural mechanisms for bacteriolysis and the self-protection against the T6SS effector Tse1. These mechanisms are significant not only by contributing to a novel understanding of niche competition among bacteria but also in providing a structural basis for antibacterial agent design and the development of new strategies to fight P. aeruginosa.     

基于复合叶片特征的计算机植物识别方法

该文探讨如何根据植物的叶片特征,利用图像处理和机器学习的方法对植物进行分类。鉴于现有的叶片分类系统多采用单一的特征,如几何和纹理等,仅能在小规模数据库上得到较好的结果。然而,随着样本种类的增多,单一特征在不同种类叶片之间的相似性非常明显,致使分类正确率降低。该研究使用多种复合特征,并提出了原创的预处理方法以及宽度、叶缘频率特征,较传统的几何特征更为详尽。研究结果显示,复合特征可以有效避免算法过拟合问题,使之适用于更大的数据库。通过提取21类植物的叶片宽度、颜色、叶缘和纹理共292维特征,对1 915张数字图像进行了分类,正确率达到93%,并分析了各类特征对分类结果的影响。研究结果表明,在不影响分类正确率前提下,可将特征减少到约100维。     

Environmental dynamics of dissolved black carbon in wetlands

Wetlands are ecosystems commonly characterized by elevated levels of dissolved organic carbon (DOC), and although they cover a surface area less than 2 % worldwide, they are an important carbon source representing an estimated 15 % of global annual DOC flux to the oceans. Because of their unique hydrological characteristics, fire can be an important ecological driver in pulsed wetland systems. Consequently, wetlands may be important sources not only of DOC but also of products derived from biomass burning, such as dissolved black carbon (DBC). However, the biogeochemistry of DBC in wetlands has not been studied in detail. The objective of this study is to determine the environmental dynamics of DBC in different fire-impacted wetlands. An intensive, 2-year spatial and temporal dynamics study of DBC in a coastal wetland, the Everglades (Florida) system, as well as one-time sampling surveys for the other two inland wetlands, Okavango Delta (Botswana) and the Pantanal (Brazil), were reported. Our data reveal that DBC dynamics are strongly coupled with the DOC dynamics regardless of location, season or recent fire history. The statistically significant linear regression between DOC and DBC was applied to estimate DBC fluxes to the coastal zone through two main riverine DOC export routes in the Everglades ecosystem. The presence of significant amounts of DBC in these three fire-impacted ecosystems suggests that sub-tropical wetlands could represent an important continental-ocean carrier of combustion products from biomass burning. The discrimination of DBC molecular structure (i.e. aromaticity) between coastal and terrestrial samples, and between samples collected in wet and dry season, suggests that spatially-significant variation in DBC source strength and/or degree of degradation may also influence DBC dynamics.     

血管外给药动力学模型残余面积的估计

以达峰时为时间单位,探讨了血管外给药-房室模型残余面积的估计问题,研究结果表明,当采样时间持续为达峰时的6倍左右,或最后采样的血药浓度小于峰浓度的20％,可保证残余面积不超过总面积的20％．