Doria, H. B. | Search bioRxiv

bioRxiv2021

Detecting Cd adaptation footprint in C. riparius with a multi-genomic approach

Evolutionary processes and acquired tolerance to toxicants are important factors governing how animals respond to chemical exposure. Evidence for increased tolerance to cadmium (Cd), a widely distributed toxic metal in aquatic environments, in Chironomus riparius is conflicting and still questioned if it happens through phenotypic plasticity or genetic adaptation. The present study considered the relevance of directional environmental changes by increasing contaminant concentration in a multigenerational selection experiment. Evaluation of measurable life-cycle traits, transcriptomic responses and quantitative genetics from an evolve and resequencing (E&R) experiment were integrated to assess the potential of C. riparius to adapt to Cd. Survival tests revealed some adaptation to Cd exposure. Genomic analyses showed a strong, genome-wide selective response in all replicates, emphasizing that even control laboratory conditions continually exert selective pressure. The integration of transcriptomic and genomic data could isolate the genes related to Cd acquired resistance. Those genes could be linked to an efflux of metals. Therefore, it is possible to conclude that C. riparius can endure long-term Cd exposure also through genetic adaptation.

genomics↗

bioRxiv2020

Measuring mutagenicity in ecotoxicology: A case study of Cd exposure in Chironomus riparius

Existing mutagenicity tests for metazoans lack the direct observation of enhanced germline mutation rates after exposure to anthropogenic substances, therefore being inefficient. Cadmium (Cd) is a metal described as a mutagen in mammalian cells and listed as a group 1 carcinogenic and mutagenic substance. But Cd mutagenesis mechanism is not yet clear. Therefore, in the present study, we propose a method coupling short-term mutation accumulation (MA) lines with subsequent whole genome sequencing (WGS) and a dedicated data analysis pipeline to investigate if chronic Cd exposure on Chironomus riparius can alter the rate at which de novo point mutations appear. Results show that Cd exposure did not affect the basal germline mutation rate nor the mutational spectrum in C. riparius, thereby arguing that exposed organisms might experience a range of other toxic effects before any mutagenic effect may occur. We show that it is possible to establish a practical and easily implemented pipeline to rapidly detect germ cell mutagens in a metazoan test organism. Furthermore, our data implicate that it is questionable to transfer mutagenicity assessments based on in vitro methods to complex metazoans. Main find of the workCd chronic exposure under environmental realistic concentrations did not exert mutagenicity; It is questionable to transfer in vitro mutagenicity assessments to complex metazoans.

pharmacology and toxicology↗