Adapt to Evolve
All living organisms are extraordinarily well-adapted to the environment in which they live. The study of the processes through which such results were achieved during evolution is a strongly debated biological issue. In particular, there are two main aspects that are still open for discussion in evolutionary biology: the speed of evolutionary mutation and selection processes and the potential of the environment to actively influence the genome, directly affecting the development and evolution of species.
According to Darwin, the environment selects the organisms that are best adapted to inhabit it based on their genetic constitution. In this context, environmental variations and genetic variability are considered as two separate phenomena. A new study coordinated by the “Charles Darwin” Department of Biology and Biotechnology reveals instead that these two phenomena are interconnected: their interaction gives rise to rapid evolutionary processes.
The study, which has been published on PNAS, experimentally demonstrates that drastic environmental changes can produce a strong genetic variability by activating special mobile elements that are similar to viral particles and known as transposons.
Discovered in the 1950s by Barbara Mc Clintock, transposons are mobile genetic elements that are capable of independently moving around the genome and changing their location either within the same chromosome or even moving to a different chromosome. Due to their capacity to finely modulate and reprogramme the expression of complex genic networks, transposons represent excellent tools for genomes to respond functionally to change and environmental stress.
Using Drosophila melanogaster as an experimental model, the researchers demonstrated that Protein HSP70 is a key mediator in the activation of transposons following environmental stress. HSP70 is a stress-induced molecular chaperone that is capable of facilitating folding (the process that gives proteins their physiological shape and function) of proteins denaturized by heat as well as compromising the functionality of the Riboprotein complex (RNA and proteins) that is normally involved in “silencing” or deactivating mobile genetic elements in the germinal line.
“The study,” explains Prof. Lucia Piacentini from the Sapienza Charles Darwin Department of Biology and Biotechnology, “reveals the functional correlation between stress, transposons and the evolution of genomes. Environmental changes act as mutagens, increasing the genetic variability through the activation of transposable elements and then act to select the most adapted genomes. Moreover, having identified the role of HSP70, a protein present in all organisms, the study provides a molecular explanation for this evolutionary view.”
In conclusion, unlike the classic Darwinian proposal, this new knowledge sheds light on the environment that acts not only to select the most suitable physiological characteristics, but also as an inducer of genetic variability mediated by the activation of mobile genetic elements.
The Hsp70 chaperone is a major player in stress-induced transposable element activation - Cappucci U., Noro F., Casale A.M., Fanti L., Berloco M., Alagia A.A., Grassi L., Le Pera L., Piacentini L., and Pimpinelli S. - PNAS September 3, 2019 116 (36) 17943-17950; first published August 9, 2019 DOI https://doi.org/10.1073/pnas.1903936116
Lucia Piacentini - firstname.lastname@example.org
"Charles Darwin" Department of Biology and Biotechnology