Genome and stresses: reactions against aggressions, behavior of transposable elements.

The action of stresses on the genome can be considered as responses of cells or organisms to external aggressions. Stress factors are of environmental origin (climatic or trophic) or of genomic nature (introduction of foreign genetic material, for example). In both cases, important perturbations can occur and modify hereditary potentialities, creating new combinations compatible with survival; such a situation may increase the variability of the genome, and allow evolutive processes to take place. The behavior of transposable elements under stress conditions is thus of particular interest, since these sequences are sources of mutations and therefore of genetic variability; they may play an important role in population adaptation. The survey of the available experimental results suggest that, although some examples of mutations and transposable elements movements induced by external factors are clearly described, environmental injuries or introduction of foreign material into a genome are not systematically followed by drastic genomic changes.