Plasticity and adaptability to the combined effect of pollution and climate change – POLLUCLIM

To reach its objectives, the project is strucutured in three Working Packages :

WP1 : Plastic response to the combined effect of temperature and pollutant gradients
We are building bidimensional niches from large gradients of temperature x pollution (the three pollutants are studied separately) within laboratory microcosms.

WP2 : Adaptability to the combined effect of temperature and pollutant gradients
We will perform experimental evolution within controlled conditions using the data from WP1 to calibrate the experiments.

WP3 : Role of stress-induced mutagenesis in adaptability
We will sequence the genomes of each tested strain from WP2 at the beginning, middle and end of the experiment.

The first major results of the project are:

1) Phenomics of Tetrahymena thermophila after exposure to heavy metals : The bioaccumulation rate is more important after exposure to zinc than to copper, resulting in larger cells.If morphology is less impacted by copper exposure, cells however swim faster and more linearly, suggesting the existence of a plastic dispersal strategy more expressed in the presence of copper than zinc. We suggest that distinct plastic resistance strategies are expressed in T. thermophila depending on the identity of heavy metal.

2) Genomics of T. thermophila: there are hotspots of mutations in the portions of MAC genomes corresponding to MIC centromeric regions, suggesting accelerated evolution of these regions. This can be explained by inter-chromosomal competions during transmission ('centromere drive'). Genes coding for proteins interacting with the extracellular environment evolve faster than the rest of the genome, suggesting important adaptability of T. thermophila to environmnental variations. This high adaptability could be linked to the high ecological success of ciliates.

Not applicable at this stage

Verdonck R, Legrand D, Jacob S, Philippe H (in press) Phenotypic plasticity through disposable genetic adaptation in ciliates. Trends in Microbiology)

Jacob S and Legrand D (2021) Phenotypic plasticity can reverse the relative extent of intra and interspecific variability across a thermal gradient. Proc R Soc B-Biol Sci, 288:20210428

Organisms have always been confronted with changes in environmental conditions, either in space or time. However, the number and rate of anthropogenic alterations impose so intense selective pressures that biodiversity is irreversibly impacted. As well, biodiversity monitoring shows that extinction rate due to global change continues to increase. Plasticity and adaptability are key eco-evolutionary processes that could mitigate biodiversity loss in the face of environmental changes. However, few studies have determined how the combined effects of anthropogenic stressors affect the immediate and evolutionary response of organisms. POLLUCLIM aims at experimentally studying a freshwater organism’s response to the combined effects of climate warming and pollution. Using laboratory microcosms of a ciliate, I will first determine the plastic response to warmer and/or polluted environments (4 different pollutants) of a panel of genotypes. I will then study the probability of evolutionary rescue to these stressors, and determine if exposure to a stressful environment influences the evolutionary response to another stressful environment. Finally, I will relate adaptive patterns to genetic backgrounds and mutagenesis effects of stressors. At the end, the project should improve our understanding of tolerance and adaptability patterns to multiple anthropogenic stressors, with access to the underlying molecular mechanisms.