Séminaire de Claudia WIEGAND (RBPE)



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Le mardi 19 janvier 2016 à 13h00, salle de l'UFR SVE, bâtiment 13, Campus de Beaulieu, UR1

Le mardi 19 janvier 2016 à 13h00, salle de l'UFR SVE, bâtiment 13, Campus de Beaulieu, UR1

Do freshwater mussel species respond differently to mixed exposure scenarios?


Abstract:

Lakes, ponds and rivers adjacent to farmland receive agrochemicals and fertilizers, creating a mixed exposure scenario for the organisms living within. With their limited spatial activity freshwater mussels cannot escape pollution and via their filtration for food, they are exposed to huge quantities of water. Whereas some indigenous species densities decline, invasive ones are able to proliferate in the same pollution scenario.
Pollution can be directly by agrochemicals, so is glyphosate one of the most used herbicides worldwide. It inhibits the amino acid synthesis in plants through the shikimic acid pathway, specific for plants and fungi. Evidence about its harmful effects in non-target organisms is growing, in particular for the commercial formulations. Pollution can also be indirectly via excess plant nutrients, thriving cyanobacterial blooms, which in turn pose a natural environmental risk due to their capacity to produce toxic metabolites. The cyanobacterial toxin microcystin-LR binds and inactivates protein phosphatase of type 1 and 2A, and may cause death of the organism. Within exposure concentration and duration limits, microcystins can be detoxified via conjugation to glutathione by the glutathione S-transferase (GST) enzymes.
Comparisons of invasive and indigenous mussel species in biotransformation of microcystin-LR and the herbicide Roundup Flash® (containing Glyphosate as a.i.) and energy allocated to that revealed some species specificities:
The invasive D. polymorpha detoxified microcystin-LR up to 50 µgLvia the sGST system but U. tumidus’ sGST were rather inhibited in the same exposure scenario. Moreover, GST was hampered in both indigenous species (U. tumidus and U. pictorum) by Roundup Flash®: it slightly decreased the GST activity, and prevented the elevation, thus the detoxification capacity in the mixed exposure.
Energetic resources supported the detoxification processes but the species drew from differen sources: Whereas U. tumidus started by using glycogen, supported by lipids after 7 days of exposure, U. pictorum needed the lipids and thus more energy right from the start. Even if closely related, these species may experience different life trait consequences via the energy that is allocated to detoxification and mending, thus lacking for growth and reproduction.
Moreover, variations of the total proteome were investigated. Using de novo sequencing, 30 spots were identified by mass spectrometry. Enzymes related to antioxidant and detoxification processes were often down regulated in U. pictorum, indicating an impairment of the mussels’ capacity to react to environmental stress.

Contact: Claudia WIEGAND

Seminaire RBPE 080116 1





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