Beyond Darwinian Selection: the Apparent Inheritance of Acquired Characters as a Result of Environmental Stress
A research group at the Department of Biology and Biotechnology of Sapienza University of Rome, reinterpreted one of the most important hypotheses on the apparent inheritability of abnormal morphological characters acquired following environmental stresses.
The study, funded by the Institute Pasteur Italia – Cenci Bolognetti Foundation and by Epigenomics Flagship Project EpiGen is published in Genetics. Despite the "general" sharing of Darwinian theory on natural selection, the hypothesis of the inheritance of acquired characters as a result of environmental factors has never completely abandoned.
One of the most famous example resembling a Lamarckian phenomenon is due to Conrad Waddington who in 1940s observed that fruit flies exposed to heat shock during metamorphosis, showed abnormal morphological traits in the adult phase. After repeated cycles of stress at each generation, these traits became inheritable, that is they were transmitted to future generations even in the absence of stress.
To explain such results in a Darwinian view, Waddington proposed that the anomalous traits raised after stress were apparently acquired because of the selection, by the same stress, of corresponding cryptic genetic mutations already present in the flies genome.
The research group of the Department of Biology and Biotechnology "Charles Darwin", formed by Laura Fanti, Lucia Piacentini, Ugo Cappucci, Assunta Maria Casale and Sergio Pimpinelli, repeated similar experiments on fruit flies Drosophila melanogaster. The results of the study, selected for the F1000Prime and published in the journal Genetics, permitted to the Sapienza team to formulate a new explanation.
Using the new molecular technologies of DNA sequencing, the researchers have shown that the abnormalities observed and fixed after repeted stresses were actually due to de novo induced genomic changes. It as been shown that heat stress is in fact able to cause mutations by breaking DNA or by activating transposable elements, particular sequences that have the ability to "jump" from one side of the genome to another.
Therefore, the inheritance of abnormal traits in response to the shock is not due to cryptic variation present in the genome, but to mechanisms of mutagenesis.
Canalization by Selection of de Novo Induced Mutations - Laura Fanti, Lucia Piacentini, Ugo Cappucci, Assunta M. Casale and Sergio Pimpinelli – Genetics, August 1, 2017 vol. 206 n.4 1995-2006; https://doi.org/10.1534/genetics.117.201079
Department of Biology and Biotechnologies “Charles Darwin”, Sapienza University di Rome
T (+39) 06 49912844/64