Project description:Microcystis aeruginosa cells were treated with phosphorus repletion, depletion and starvation. Isobaric tags for relative and absolute quantitation (iTRAQ) proteomic method was employed to explore to the effects of phosphorus limitation on Microcystis aeruginosa cells at the protein level. This investigation would contribute to the understanding of global cellular responses of Microcystis to phosphorus limitation and provide theoretical basis for deciding whether it is an effective way to control Microcystis blooms by phosphorus reduction.
Project description:Although cyanobacteria produce a wide range of natural toxins that impact aquatic organisms, food webs and water quality, the mechanisms of toxicity are still insufficiently understood. Here, we implemented a whole-genome expression microarray to identify pathways, gene networks and paralogous gene families responsive to Microcystis stress in Daphnia pulex. Therefore, neonates of a sensitive isolate were given a diet contaminated with Microcystis to contrast with those given a control diet for sixteen days. The microarray revealed 2247 differentially expressed (DE) genes (7.6% of the array) in response to Microcystis, of which 17% are lineage specific and 49% are gene duplicates (paralogs). We identified four pathways/gene networks and eight paralogous gene families affected by Microcystis. Differential regulation of the ribosome including 3 paralogous gene families encoding 40S, 60S and mitochondrial ribosomal proteins, suggests an impact of Microcystis on protein synthesis of Daphnia. In addition, differential regulation of the oxidative phosphorylation pathway, including the NADH ubquinone oxidoreductase gene family, and trypsin paralogous gene family, major component of the digestive system in Daphnia, could explain why fitness is reduced based on energy budget considerations. For others (.e.g Neurexin IV), a link with fitness remains to be established.
Project description:Although cyanobacteria produce a wide range of natural toxins that impact aquatic organisms, food webs and water quality, the mechanisms of toxicity are still insufficiently understood. Here, we implemented a whole-genome expression microarray to identify pathways, gene networks and paralogous gene families responsive to Microcystis stress in Daphnia pulex. Therefore, neonates of a sensitive isolate were given a diet contaminated with Microcystis to contrast with those given a control diet for sixteen days. The microarray revealed 2247 differentially expressed (DE) genes (7.6% of the array) in response to Microcystis, of which 17% are lineage specific and 49% are gene duplicates (paralogs). We identified four pathways/gene networks and eight paralogous gene families affected by Microcystis. Differential regulation of the ribosome including 3 paralogous gene families encoding 40S, 60S and mitochondrial ribosomal proteins, suggests an impact of Microcystis on protein synthesis of Daphnia. In addition, differential regulation of the oxidative phosphorylation pathway, including the NADH ubquinone oxidoreductase gene family, and trypsin paralogous gene family, major component of the digestive system in Daphnia, could explain why fitness is reduced based on energy budget considerations. For others (.e.g Neurexin IV), a link with fitness remains to be established. RNA was isolated from three independent and concurrently replicated exposures of Daphnia to control and Microcystis conditions. RNA was hybridized to 4 microarrays using a standard, control vs. treated design that included dye swaps.
Project description:Microcystins are produced by the cyanobacteria, most commonly Microcystis aerµginosa. Upon ingestion, toxic microcystins are actively absorbed by fish, birds and mammals where they are primarily liver toxins.
Project description:Little is known about the influence that environmental stressors may have on genome-wide methylation patterns, and to what extent epigenetics may be involved in environmental stress response. Yet, studies of methylation patterns under stress could provide crucial insights on stress response and toxicity pathways. Here, we focus on genome-wide methylation patterns in the micro-crustacean Daphnia magna, a model organism in ecotoxicology and risk assessment, exposed to the toxic cyanobacterium Microcystis aeruginosa. Bisulfite sequencing of exposed and control animals highlighted differential methylation patterns in Daphnia upon exposure to Microcystis primarily in exonic regions. These patterns are enriched for serine/threonine amino acid codons and genes related to protein synthesis, transport and degradation. Furthermore, we observed that genes with differential methylation corresponded well with genes susceptible to alternative splicing in response to Microcystis stress. Overall, our results suggest a complex mechanistic response in Daphnia characterized by interactions between DNA methylation and gene regulation mechanisms. These results underscore that DNA methylation is modulated by environmental stress and can also be an integral part of the toxicity response in our study species.