Early response to nanoparticles in the Arabidopsis transcriptome compromises plant defence and root-hair development through salicylic acid signalling

Background: The impact of nano-scaled materials on photosynthetic organisms needs to be evaluated. Plants represent the largest interface between the environment and biosphere, so understanding how nanoparticles affect them is especially relevant for environmental assessments. Nanotoxicology studies in plants allude to quantum size effects and other properties specific of the nano-stage to explain increased toxicity respect to bulk compounds. However, gene expression profiles after exposure to nanoparticles and other sources of environmental stress have not been compared and the impact on plant defence has not been analysed. Results: Arabidopsis plants were exposed to TiO2-nanoparticles, Ag-nanoparticles, and multi-walled carbon nanotubes as well as different sources of biotic (microbial pathogens) or abiotic (saline, drought, or wounding) stresses. Changes in gene expression profiles and plant phenotypic responses were evaluated. Transcriptome analysis shows similarity of expression patterns for all plants exposed to nanoparticles and a low impact on gene expression compared to other stress inducers. Nanoparticle exposure repressed transcriptional responses to microbial pathogens, resulting in increased bacterial colonization during an experimental infection. Inhibition of root hair development and transcriptional patterns characteristic of phosphate starvation response were also observed. The exogenous addition of salicylic acid prevented some nano-specific transcriptional and phenotypic effects, including the reduction in root hair formation and the colonization of distal leaves by bacteria. Conclusions: This study integrates the effect of nanoparticles on gene expression with plant responses to major sources of environmental stress and paves the way to remediate the impact of these potentially damaging compounds through hormonal priming.

Ecological modeling for all

A brief review of the status of the ECOPATH modeling approach and software is presented, with emphasis on the recent release of a Windows version (ECOPATH 3.0), which enables consideration of uncertainties, and sets the stage for simulation modeling using ECOSIM. Modeling of coral reefs is emphasized.

Sensing parasites: proteomic and advanced bio-detection alternatives

[EN] Parasitic diseases have a great impact in human and animal health. The gold standard for the diagnosis of the majority of parasitic infections is still conventional microscopy, which presents important limitations in terms of sensitivity and specificity and commonly requires highly trained technicians. More accurate molecular-based diagnostic tools are needed for the implementation of early detection, effective treatments and massive screenings with high-throughput capacities. In this respect, sensitive and affordable devices could greatly impact on sustainable control programmes which exist against parasitic diseases, especially in low income settings. Proteomics and nanotechnology approaches are valuable tools for sensing pathogens and host alteration signatures within microfluidic detection platforms. These new devices might provide novel solutions to fight parasitic diseases. Newly described specific parasite derived products with immune-modulatory properties have been postulated as the best candidates for the early and accurate detection of parasitic infections as well as for the blockage of parasite development. This review provides the most recent methodological and technological advances with great potential for biosensing parasites in their hosts, showing the newest opportunities offered by modern “-omics” and platforms for parasite detection and control.

Comportamento tribocorrosivo do aço inoxidável e de ligas de titânio em meio salino

No presente trabalho, foram realizados ensaios de tribocorrosão no aço inoxidável AISI 304L, no titânio comercialmente puro (CPTi) e na liga de titânio Ti6Al4V em solução aquosa de 0,90% m/v NaCl. Amostras de ligas de titânio com tratamento térmico superficial de refusão a laser também foram utilizadas. Um tribômetro do tipo pino-no-disco com contracorpo de alumina foi usado. Técnicas eletroquímicas in situ de monitoramento em circuito aberto, espectroscopia de impedância eletroquímica, curvas de polarização e amperimetria de resistência nula foram empregadas. Os resultados obtidos indicam que o desgaste tribocorrosivo das ligas de titânio é mais intenso do que o observado no aço inoxidável, apresentando perfis de superfície mais irregulares. A análise da impedância eletroquímica mostrou que todos os materiais utilizados apresentam uma rápida recuperação da camada passiva, exibindo módulos e fases um pouco menores do que os medidos antes do desgaste. Sob atrito, os diagramas de impedância apresentam uma forte redução do módulo. Sob desgaste, o expoente α do elemento de fase constante (CPE) atinge seu valor mais baixo, enquanto o parâmetro γ é máximo. As curvas de polarização exibem potenciais menores e densidades de corrente de corrosão maiores durante o desgaste. O tratamento de refusão a laser, embora mude a microestrutura e a dureza superficial das amostras, não indica uma mudança aparente nos parâmetros eletroquímicos sob tribocorrosão, bem como do coeficiente de atrito. Nos ensaios de amperimetria de resistência nula, foi possível estimar a corrente mensurada no ARN por meio do emprego de um circuito elétrico equivalente. A densidade espectral de potência dos sinais de potencial e de corrente exibe a frequência de rotação (1,25 Hz) e seus harmônicos. Para baixas frequências (abaixo de 10 mHz), o decaimento obedece à relação 1 ⁄ e 1⁄ para os sinais de potencial e corrente, respectivamente.