Project description:Chemical contamination is a common threat to biota thriving in estuarine and coastal ecosystems. In particular, trace metals tend to accumulate and exert deleterious effects on small invertebrates such as zooplankton, which are essential trophic links between phytoplankton and higher-level consumers in aquatic food webs. Beyond the direct effects of the contamination, we hypothesized that metal exposure could also affect the zooplankton microbiota, which in turn might further impair host fitness. To assess this assumption, copepods (Eurytemora affinis) were sampled in the oligo-mesohaline zone of the Seine estuary and exposed to dissolved copper (25 µg.L-1) over a 72-hour time period. Copepod response to copper treatment was assessed by determining transcriptomic changes in E. affinis along with shifts in its microbiota. Unexpectedly, very few genes were differentially expressed in copper-treated copepods compared to controls, with most of the reported differences involving genes upregulated in males compared to females. In contrast, copper increased the taxonomic diversity indices of the microbiota and resulted in substantial compositional changes at both the phyla and genus levels. Phylogenetic reconstruction of the microbiota further suggested that copper mitigated phylogenetic relatedness of taxa at the basal tree structure of the phylogeny, whereas it strengthened it at the terminal branches. Increased terminal phylogenetic clustering in copper-treated copepods concurred with higher proportions of bacterial genera previously identified as copper resistant (e.g., Pseudomonas, Acinetobacter, and Alkanindiges) and a higher relative abundance of the copA gene encoding a periplasmic inducible multi-copper oxidase. Overall, these results revealed very contrasting responses of E. affinis and its microbiota to copper exposure. The enrichment in micro-organisms likely to perform copper sequestration and/or enzymatic transformation processes, underlines here the need to follow the microbial component during the evaluation of the vulnerability of the zooplankton to the metallic stress.
Project description:Copepods are zooplanktonic crustaceans ubiquitously widespread in aquatic systems. They are of ecological importance due to their place in the trophic chain. Copepods are exposed to a wide variety of pollutants as insect growth regulators (IGR) acting as endocrine disruptors although they are not the target. The aim of the present work was to investigate the molecular response of a non-targeted organism, the copepod Eurytemora affinis, to an IGR. Adult males and females were exposed at two sub-lethal concentrations of tebufenozide (TEB), an agonist of the ecdysone receptor targeting lepidopteran larvae. Results suggest a gender-specific response with a higher sensitivity in males potentially due to a differential activation of stress response pathways. Indeed, genes coding for proteins involved in stress response were mis-regulated in males while not in females suggesting that detoxification processes are still ongoing in males. In both genders, TEB exposure triggers similar pathways as for its targeted species by modulating the transcription of early and late ecdysone responsive genes. Among them, genes involved in cuticle metabolism, muscle contraction, neurotransmission and gametogenesis whose mis-regulation could lead to moult, locomotor and reproductive impairments. Furthermore, genes coding for proteins playing part in epigenetic processes were found in both genders highlighting the potential impact of TEB exposure on further generations. Beyond the in-depth knowledge of the molecular MoA of an ecdysone agonist on a non-targeted organism, this work provides data allowing the identification of (i) potential biomarkers of ecdysone agonists and (ii) putative physiological responses to be further assessed to characterize the effects of TEB at higher biological levels. The present study reinforces the suitability of the use E. affinis as an ecotoxicological model.
Project description:Plum pox virus (PPV, family Potyviridae) is one of the most important viral pathogens of Prunus spp. causing considerable damage to stone-fruit industry worldwide each year. Among the PPV strains identified so far, only PPV-C and PPV-CR are able to infect cherries under natural conditions. Herein, we evaluated the impact of strains differing by the pathogenic potential on herbaceous host Nicotiana benthamiana. At first glance, a faster accumulation of PPV capsid protein was noticed by semi-quantitative DAS-ELISA on tobacco leaves infected by PPV-CR (the RU-30sc isolate) in contrast to PPV-C (BY-101 isolate). This result was correlated perfectly with observed phenotypic symptoms. To assess the host response to infection more deeply, a comprehensive proteomic profiling was performed using reverse phase UHPLC followed by label-free mass spectrometry quantification. Thirty-one unique plant proteins were identified as significantly altered due to the infection. Precise evaluation of particular amount shifts of identified proteins in relation to infection has revealed that the aggressive PPV-CR isolate has a stronger influence on the abundance of photosynthesis-related proteins, mainly from Calvin cycle, as the mild PPV-C. This observation was accompanied by a significant reduction of photosynthetic pigments extracted from the leaves of PPV-CR infected plants. Shifts in the abundance of remaining identified proteins, indicates activation of repair mechanism, stimulation of photosynthetic capacity, and modifications in amino acid and carbohydrate metabolism to affect plant growth and initiate energy formation via gluconeogenesis. Furthermore, we speculate that accumulation of H2O2, in PPV-CR infected leaves may activate glutathione synthesis, which plays a crucial role in further plant defense and development.