Can allelopathic potentialities of Mediterranean plant species reduce the spread of invasive plant species, Acacia dealbata and Ailanthus altissima?

Beyond ecological and health impacts, invasive alien plant species can generate indirect and direct costs, notably through reduced agricultural yields, restoration, and management of the invaded environment. Acacia dealbata and Ailanthus altissima are invasive plant species that cause particularly significant damage to the railway network in the Mediterranean area. The allelopathic properties of Mediterranean plant species could be used as nature-based solutions to slow down the spread of such invasive plant species along railway borders. In this context, a mesocosm experiment was set-up: (i) to test the potential allelopathic effects of Cistus ladanifer, Cistus albidus, and Cotinus coggygria leaf aqueous extracts on seed germination and seedling growth of A. dealbata and A. altissima; (ii) to evaluate whether these effects depend on the extract dose; and finally, (iii) to estimate whether these effects are modified by soil amendment. Leaf aqueous extracts of the three native plant species showed negative effects on both seed germination and seedling growth of the two invasive species. Our results show that the presence of allelochemicals induces a delay in seed germination (e.g., A. dealbata germination lasted up to 269% longer in the presence of high-dose leaf aqueous extracts of C. coggygria), which can lead to a decrease in individual recruitment. They also highlight a decrease in seedling growth (e.g., high-dose C. coggygria leaf aqueous extracts induced a 26% decrease in A. dealbata radicle growth), which can alter the competitiveness of invasive species for resource access. Our results also highlight that compost addition limits the inhibitory effect of native Mediterranean plants on the germination of invasive alien plants, suggesting that soil organic matter content can counteract allelopathic effects on invasive alien plants. Thus, our findings revealed that the allelopathic potential of certain Mediterranean plant species could be a useful tool to manage invasive plant species.

Heavy ionic pollution disrupts assemblages of algae, macroinvertebrates and riparian vegetation.

Urban streams display consistent ecological symptoms that commonly express degraded biological, physical, and chemical conditions: the urban stream syndrome (USS). Changes linked to the USS result in consistent declines in the abundance and richness of algae, invertebrates, and riparian vegetation. In this paper, we assessed the impacts of extreme ionic pollution from an industrial effluent in an urban stream. We studied the community composition of benthic algae and benthic invertebrates and the indicator traits of riparian vegetation. The dominant pool of benthic algae, benthic invertebrates and riparian species were considered as euryece. However, ionic pollution impacted these three biotic compartments' communities, disrupting these tolerant species assemblages. Indeed, after the effluent, we observed the higher occurrence of conductivity-tolerant benthic taxa, like Nitzschia palea or Potamopyrgus antipodarum and plant species reflecting nitrogen and salt contents in soils. Providing insights into organisms' responses and resistance to heavy ionic pollution, this study sheds light on how industrial environmental perturbations could alter the ecology of freshwater aquatic biodiversity and riparian vegetation.

Genetic network analyzer: a tool for the qualitative modeling and simulation of bacterial regulatory networks.

Genetic Network Analyzer (GNA) is a tool for the qualitative modeling and simulation of gene regulatory networks, based on so-called piecewise-linear differential equation models. We describe the use of this tool in the context of the modeling of bacterial regulatory networks, notably the network of global regulators controlling the adaptation of Escherichia coli to carbon starvation conditions. We show how the modeler, by means of GNA, can define a regulatory network, build a model of the network, determine the steady states of the system, perform a qualitative simulation of the network dynamics, and analyze the simulation results using model-checking tools. The example illustrates the interest of qualitative approaches for the analysis of the dynamics of bacterial regulatory networks.

Hijacking hepatitis C viral replication with a non-coding replicative RNA.

The current treatments used against RNA viruses have a limited efficacy and are often hampered by the induction of side-effects. The specific delivery of antiviral proteins in infected cells should increase their efficiency and reduce their impact on healthy cells. Here, we describe the development of a new approach which takes advantage of the viral replication machinery to specifically target the antiviral protein expression to the infected cells. The strategy is based on the delivery of a non-coding (-)RNA carrying the structures required for the binding of the viral replication complex and the complementary sequence of an antiviral gene. The viral replication complex replicates the (-)RNA similarly to the viral genome to give a coding (+)RNA from which the antiviral protein will be expressed. As non-infected cells do not express the replication complex, this specific machinery can be used to target virus-infected cells without affecting healthy cells. We show that this approach can be successfully applied to the hepatitis C virus. In both replicon-harboring cells (genotype 1b) and JFH-1 infected cells (genotype 2a), nrRNAs induced a strong decrease in genomic RNA and viral protein NS5A. These effects were correlated with a strong activation of several interferon-stimulating genes.

A service-oriented architecture for integrating the modeling and formal verification of genetic regulatory networks.

BACKGROUND: The study of biological networks has led to the development of increasingly large and detailed models. Computer tools are essential for the simulation of the dynamical behavior of the networks from the model. However, as the size of the models grows, it becomes infeasible to manually verify the predictions against experimental data or identify interesting features in a large number of simulation traces. Formal verification based on temporal logic and model checking provides promising methods to automate and scale the analysis of the models. However, a framework that tightly integrates modeling and simulation tools with model checkers is currently missing, on both the conceptual and the implementational level. RESULTS: We have developed a generic and modular web service, based on a service-oriented architecture, for integrating the modeling and formal verification of genetic regulatory networks. The architecture has been implemented in the context of the qualitative modeling and simulation tool GNA and the model checkers NUSMV and CADP. GNA has been extended with a verification module for the specification and checking of biological properties. The verification module also allows the display and visual inspection of the verification results. CONCLUSIONS: The practical use of the proposed web service is illustrated by means of a scenario involving the analysis of a qualitative model of the carbon starvation response in E. coli. The service-oriented architecture allows modelers to define the model and proceed with the specification and formal verification of the biological properties by means of a unified graphical user interface. This guarantees a transparent access to formal verification technology for modelers of genetic regulatory networks.

Seven nucleotide changes characteristic of the hepatitis C virus genotype 3 5' untranslated region: correlation with reduced in vitro replication.

Computer analysis of 158 hepatitis C virus (HCV) 5' untranslated region (5' UTR) sequences from the six genotypes showed that the 5' UTR from genotype 3 displays seven specific non-contiguous nucleotide changes, at positions 8, 13, 14, 70, 97, 203 and 224. The purpose of this study was to investigate the impact of these changes on translation and replication activities. Indeed, these modifications could alter both the internal ribosome entry site (IRES) present in the 5' UTR of the plus-strand RNA and the 3' end of the minus strand involved in the initiation of plus-strand RNA synthesis. We found that the genotype 3-specific nucleotide changes do not modify the in vitro or ex vivo translation activity of the corresponding IRES, in comparison with that of genotype 1. In contrast, in vitro replication from the minus-strand RNA is eight times less efficient for genotype 3 than for genotype 1 RNA, suggesting the involvement of some nucleotide changes in the reduction of RNA synthesis. Nucleotides 13, 14 and 224 were found to be responsible for this effect. Moreover, a reduced replicative activity was confirmed ex vivo for genotype 3, but to a lesser extent than that observed in vitro, using an RNA minigenome.

A promoter activity is present in the DNA sequence corresponding to the hepatitis C virus 5' UTR.

The hepatitis C virus (HCV) 5' untranslated region (UTR) has been extensively studied with regard to its internal ribosomal entry site (IRES) activity. In this work we present results suggesting the existence of a strong promoter activity carried by the DNA sequence corresponding to the HCV 5' UTR. This activity was not detected when the HCV 5' UTR sequence was replaced by HCV 3' UTR or poliovirus 5' UTR sequences. These results were further confirmed by using bicistronic constructions. We demonstrated the presence of an mRNA initiated in this 5' UTR sequence and located the initiation site by the 5' RACE method at nucleotide 67. Furthermore, northern experiments and flow cytometry analysis showed the unambiguous activity of such a promoter sequence in stably transfected cells. Our results strongly suggest that the data obtained using bicistronic DNA constructs carrying the HCV 5' UTR should be analyzed not only at the translational but also at the transcriptional level.