Nitric Oxide Accumulation: The Evolutionary Trigger for Phytopathogenesis

Many publications highlight the importance of nitric oxide (NO) in plant–bacteria interactions, either in the promotion of health and plant growth or in pathogenesis. However, the role of NO in the signaling between bacteria and plants and in the fate of their interaction, as well as the reconstruction of their interactive evolution, remains largely unknown. Despite the complexity of the evolution of life on Earth, we explore the hypothesis that denitrification and aerobic respiration were responsible for local NO accumulation, which triggered primordial antagonistic biotic interactions, namely the first phytopathogenic interactions. N-oxides, including NO, could globally accumulate via lightning synthesis in the early anoxic ocean and constitute pools for the evolution of denitrification, considered an early step of the biological nitrogen cycle. Interestingly, a common evolution may be proposed for components of denitrification and aerobic respiration pathways, namely for NO and oxygen reductases, a theory compatible with the presence of low amounts of oxygen before the great oxygenation event (GOE), which was generated by Cyanobacteria. During GOE, the increase in oxygen caused the decrease of Earth’s temperature and the consequent increase of oxygen dissolution and availability, making aerobic respiration an increasingly dominant trait of the expanding mesophilic lifestyle. Horizontal gene transfer was certainly important in the joint expansion of mesophily and aerobic respiration. First denitrification steps lead to NO formation through nitrite reductase activity, and NO may further accumulate when oxygen binds NO reductase, resulting in denitrification blockage. The consequent transient NO surplus in an oxic niche could have been a key factor for a successful outcome of an early denitrifying prokaryote able to scavenge oxygen by NO/oxygen reductase or by an independent heterotrophic aerobic respiration pathway. In fact, NO surplus could result in toxicity causing “the first disease” in oxygen- producing Cyanobacteria. We inspected in bacteria the presence of sequences similar to the NO-producing nitrite reductase nirS gene of Thermus thermophilus, an extreme thermophilic aerobe of the Thermus/Deinococcus group, which constitutes an ancient lineage related to Cyanobacteria. In silico analysis revealed the relationship between the presence of nirS genes and phytopathogenicity in Gram-negative bacteria.info:eu-repo/semantics/publishedVersio

Finding optimal microorganisms to increase crop productivity and sustainability under drought – a structured reflection

Considering the more frequent and longer drought events due to climate change, improving plant drought tolerance became a priority. The search for plant growth promoting rhizobacteria (PGPR) able to improve plant drought tolerance has been long addressed, but with inconsistent results. Here, we summarize the PGPR mechanisms that improve plant drought tolerance, identify the pitfalls in current PGPR isolation and selection routines, and discuss the key points to define new strategies to get optimal PGPR for plant drought tolerance. Drought and host genotype impact rhizo-communities, and host-mediated selection strategies may be used to obtain a drought-adapted rhizomicrobiome that can be a source for PGPR isolation. Alternatively, an integrated omics-level analysis can improve our knowledge on the mechanisms of rhizomicrobiome construction, and a targeted approach can be designed, which will be focused on key PGP traits. New strategies to build PGPR consortia for improvement of plant drought tolerance are also suggested.info:eu-repo/semantics/publishedVersio

Discussing impact assessment on creative tourism: A theoretical and analytical model

Over the last decades, tourism has experienced exponential growth, expansion and diversification, being considered one of the most important socio-economic sectors, an essential source of income and employment for many territories (e.g. Bellini et al. 2017; Romão and Nijkamp 2017; Weidenfeld 2018). In response to the concerns about the negative impacts of tourism and to improve the relationship between hosts and tourists, culture-based creativity is seen as a path to create competitive advantages and improve more sustainable practices in the tourism field. Therefore, many cities and regions have sought to reinvent themselves as creative tourist destinations, by encouraging synergies between tourism and the cultural and creative activities to foster the development of new products, experiences and markets (Delisle and Jolin 2007; Duxbury and Richards 2019; Richards and Wilson 2007). Despite the high attractiveness of large capitals and metropolises, small towns and rural areas can also benefit from the growth of tourist flows and the demand for less overcrowded tourist destinations. Alternatively, they can offer interactive, small-scale, unique and tailor-made experiences based on local culture, lifestyles, and values thus generating potential positive impacts on these communities (Richards and Duif 2018; Wisansing and Vongvisitsin 2019). In the discussion of tourism development models, sustainability has become an unavoidable frame of reference, introducing cultural, social and environmental concerns, in addition to the analysis of economic issues. In this vein, we consider the integration of culture as a fundamental dimension of the analysis, together and in interrelation with the economic, social and environmental dimensions. Although the impact assessment exercises have focused on predominantly economic indicators, there is an increasing number of methods that can determine and monitor more accurately the multiple links and impacts of tourist activities in local communities, and also address sustainability issues. This paper has the objective of review the main theoretical and methodological approaches about impact assessment, to develop a comprehensive and operational framework capable of contributing to a better understanding the multifaced nature of creative tourism and their diverse impacts to support the formulation of policies for the sector and according to each context.FCT; FEDE

Modelação da qualidade microbiológica da água na Ria Formosa

Este estudo integra-se numa avaliação hidrodinâmica e monitorização microbiológica da qualidade da água da Ria Formosa. A monitorização foi implementada pela DRAOT Algarve com a colaboração da EST, da FCMA e do IST. A metodologia utilizada consiste na aplicação de um modelo matemático para simulação das variáveis hidrodinâmicas e da qualidade da água. Utilizam-se como traçadores os coliformes fecais (CF), considerados indicadores de contaminação fecal pelo Dec-Lei 236/98 de 1 de Agosto, relativo à qualidade de águas do litoral e salobras para fins aquícolas- águas conquícolas. As águas da ria são usadas para cultura de diversas espécies conquícolas de bivalves. Estes são organismos que filtram e retêm no seu interior material particulado existente em suspensão na água tais como os CF entre outros microorganismos presentes na água. Para avaliar a concentração de coliformes nos bivalves e gastrópodes foi desenvolvido um modelo que simula a bioacumulação desta propriedade por parte do bivalve. Da sua aplicação permite classificar a Ria em várias classes conforme o estabelecido no Dec. Lei nº 293/98 de 18 de Setembro

Dexamethasone prevents granulocyte-macrophage colony-stimulating factor-induced nuclear factor-kappaB activation, inducible nitric oxide synthase expression and nitric oxide production in a skin dendritic cell line.

AIMS: Nitric oxide (NO) has been increasingly implicated in inflammatory skin diseases, namely in allergic contact dermatitis. In this work, we investigated the effect of dexamethasone on NO production induced by the epidermal cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) in a mouse fetal skin dendritic cell line. METHODS: NO production was assessed by the method of Griess. Expression of the inducible isoform of nitric oxide synthase (iNOS) protein was evaluated by western blot analysis and immunofluorescence microscopy. Western blot analysis was also performed to evaluate cytosolic IkappaB-alpha (IkappaB-alpha) protein levels. The electrophoretic mobility shift assay was used to evaluate the activation or inhibition of nuclear factor kappa B (NF-kappaB). RESULTS: GM-CSF induced iNOS expression and NO production, and activated the transcription factor NF-kappaB. Dexamethasone inhibited, in a dose-dependent manner, NO production induced by GM-CSF. Addition of dexamethasone to the culture, 30 min before GM-CSF stimulation, significantly inhibited the cellular expression of iNOS. Dexamethasone also inhibited GM-CSF-induced NF-kappaB activation by preventing a significant decrease on the IkappaB-alpha protein levels, thus blocking NF-kappaB migration to the nucleus. CONCLUSIONS: The corticosteroid dexamethasone inhibits GM-CSF-induced NF-kappaB activation, iNOS protein expression and NO production. These results suggest that dexamethasone is a potent inhibitor of intracellular events that are involved on NO synthesis, in skin dendritic cells

Achromobacter xylosoxidans and Enteromorpha intestinalis Extract Improve Tomato Growth under Salt Stress

The effect of seed coating salt-stressed tomato with the bacterium Achromobacter xylosoxidans BOA4 and/or irrigation with an extract of the marine algae Enteromorpha intestinalis (EI) is herein evaluated. The plant shoots and roots were harvested separately on day 50, following extensive saline stress. The addition of BOA4 and/or EI extract resulted in an average increase of 33% in plant shoot DW, but an averaged decrease of 44% in the root to shoot biomass ratio. Anthocyanin content increased by over 34% and 44% with EI and BOA4 plus EI treatments, respectively. Since enhanced protein tyrosine nitration (PTN) is a known plant response to salt stress, the PTN level was inspected through 3-nitrotyrosine content determination. This was drastically increased by salt stress; however, BOA4, EI or both caused an averaged PTN decrease of 30% in stressed roots or shoots. This PTN response could be associated with tomato phenotypic characteristics and is postulated to be inversely correlated to cytokinin contents in stressed plants, namely cis-zeatin-type-cis-zeatin (cZ) plus cis-zeatin riboside (cZR), and isopentenyladenine (iP). The latter showed a drastic average increase by 3.6-fold following BOA4 and/or EI treatments of salinized tomato. This increment could be related to cytokinin biosynthesis induced by the applied bio-stimulants; IP and derivatives are the main cytokinins in seaweeds, and Achromobacter xylosoxidans BOA4 was shown to produce up to 17.5 pmol mL−1 of isopentenyladenine. This work is the first report on the influence of bio-stimulants, used to improve salt stress tolerance, on plant PTN levels; BOA4 and/or EI treatments decreased PTN, while increasing cis-zeatin-type and iP cytokinins in tomato, the latter showed an enhanced tolerance to salt stress.info:eu-repo/semantics/publishedVersio

The Plant Growth-Promoting Potential of Halotolerant Bacteria Is Not Phylogenetically Determined: Evidence from Two Bacillus megaterium Strains Isolated from Saline Soils Used to Grow Wheat

1) Background: Increasing salinity, further potentiated by climate change and soil degra- dation, will jeopardize food security even more. Therefore, there is an urgent need for sustainable agricultural practices capable of maintaining high crop yields despite adverse conditions. Here, we tested if wheat, a salt-sensitive crop, could be a good reservoir for halotolerant bacteria with plant growth-promoting (PGP) capabilities. (2) Methods: We used two agricultural soils from Algeria, which differ in salinity but are both used to grow wheat. Soil halotolerant bacterial strains were isolated and screened for 12 PGP traits related to phytohormone production, improved nitrogen and phosphorus availability, nutrient cycling, and plant defence. The four ‘most promising’ halotolerant PGPB strains were tested hydroponically on wheat by measuring their effect on germination, sur- vival, and biomass along a salinity gradient. (3) Results: Two halotolerant bacterial strains with PGP traits were isolated from the non-saline soil and were identified as Bacillus subtilis and Pseudomonas fluorescens, and another two halotolerant bacterial strains with PGP traits were isolated from the saline soil and identified as B. megaterium. When grown under 250 mM of NaCl, only the inoculated wheat seedlings survived. The halotolerant bacterial strain that displayed all 12 PGP traits and promoted seed germination and plant growth the most was one of the B. megaterium strains isolated from the saline soil. Although they both belonged to the B. megaterium clade and displayed a remarkable halotolerance, the two bacterial strains isolated from the saline soil differed in two PGP traits and had different effects on plant performance, which clearly shows that PGP potential is not phylogenetically determined. (4) Conclusions: Our data highlight that salt-sensitive plants and non-saline soils can be reservoirs for halotolerant microbes with the potential to become effective and sustainable strategies to improve plant tolerance to salinity. However, these strains need to be tested under field conditions and with more crops before being considered biofertilizer candidates.info:eu-repo/semantics/publishedVersio

Efeito dos abusos de temperatura no teor de ácido ascórbico em agrião congelado ao longo da cadeia de distribuição

Este trabalho consistiu no estudo do efeito dos abusos de temperatura no teor de ácido ascórbico (AA) em agrião congelado ao longo da cadeia de distribuição. Para tal, simulou-se um conjunto de condições a que os produtos congelados são sujeitos desde a saída da fábrica até ao consumidor. O agrião, antes do processo de congelação, foi branqueado a uma temperatura de 95 ºC durante 20 s, para uma redução de 90% na actividade específica da enzima peroxidase. O teor de ácido ascórbico do agrião congelado foi determinado ao longo do plano de abusos de temperatura, baseado numa situação real e comparado com um modelo de previsão, usando os parâmetros cinéticos determinados em condições isotérmicas. Verificou-se que durante os abusos de temperatura o teor de AA sofreu oscilações, mas não apresentou grandes alterações no final do plano a que foi submetido. Alguns pontos experimentais e o valor final do teor de ácido ascórbico do agrião congelado abusado foram semelhantes aos valores previstos, apesar de na maior parte dos casos os valores experimentais terem sido superiores aos previstos. O processo de branqueamento, apesar de ter sido responsável por degradar o ácido ascórbico, contribuiu para a estabilidade do agrião ao longo do armazenamento. Este tipo de estudos são uma ferramenta importante, pois permitem a previsão de resultados de diferentes cenários de armazenamento e condições de distribuição, e assim poderão contribuir para a melhoria da qualidade dos produtos congelados e para o estabelecimento de melhores condições da cadeia de frio

Co-precipitation synthesis of stable iron oxide nanoparticles with NaOH: New insights and continuous production via flow chemistry

Co-precipitation is by far the most common synthesis for magnetic iron oxide nanoparticles (IONPs), as cheap and environmentally friendly precursors and simple experimental procedures facilitate IONP production in many labs. Optimising co-precipitation syntheses remains challenging however, as particle formation mechanisms are not well understood. This is partly due to the rapid particle formation (within seconds) providing insufficient time to characterise initial precipitates. To overcome this limitation, a flow chemistry approach has been developed using steady-state operation to “freeze” transient reaction states locally. This allowed for the first time a comprehensive analysis of the early stages of co-precipitation syntheses via in-situ Small Angle X-ray Scattering and in-situ synchrotron X-Ray Diffraction. These studies revealed that after mixing the ferrous/ferric chloride precursor with the NaOH base solution, the most magnetic iron oxide phase forms within 5 s, the particle size changes only marginally afterwards, and co-precipitation and agglomeration occur simultaneously. As these agglomerates were too large to achieve colloidal stability via subsequent stabiliser addition, co-precipitated IONPs had to be de-agglomerated. This was achieved by adding the appropriate quantity of a citric acid solution which yielded within minutes colloidally stable IONP solutions around a neutral pH value. The new insights into the particle formation and the novel stabilisation procedure (not requiring any ultra-sonication or washing step) allowed to design a multistage flow reactor to synthesise and stabilise IONPs continuously with a residence time of less than 5 min. This reactor was robust against fouling and produced stable IONP solutions (of ~1.5 mg particles per ml) reproducibly via fast mixing ( 500 ml/h) for low materials cost

Activation of Dopaminergic D2/D3 Receptors Modulates Dorsoventral Connectivity in the Hippocampus and Reverses the Impairment of Working Memory after Nerve Injury

Dopamine plays an important role in several forms of synaptic plasticity in the hippocampus, a crucial brain structure for working memory (WM) functioning. In this study, we evaluated whether the working-memory impairment characteristic of animal models of chronic pain is dependent on hippocampal dopaminergic signaling. To address this issue, we implanted multichannel arrays of electrodes in the dorsal and ventral hippocampal CA1 region of rats and recorded the neuronal activity during a food-reinforced spatial WM task of trajectory alternation. Within-subject behavioral performance and patterns of dorsoventral neuronal activity were assessed before and after the onset of persistent neuropathic pain using the Spared Nerve Injury (SNI) model of neuropathic pain. Our results show that the peripheral nerve lesion caused a disruption in WM and in hippocampus spike activity and that this disruption was reversed by the systemic administration of the dopamine D2/D3 receptor agonist quinpirole (0.05 mg/kg). In SNI animals, the administration of quinpirole restored both the performance-related and the task-related spike activity to the normal range characteristic of naive animals, whereas quinpirole in sham animals caused the opposite effect. Quinpirole also reversed the abnormally low levels of hippocampus dorsoventral connectivity and phase coherence. Together with our finding of changes in gene expression of dopamine receptors and modulators after the onset of the nerve injury model, these results suggest that disruption of the dopaminergic balance in the hippocampus may be crucial for the clinical neurological and cognitive deficits observed in patients with painful syndromes