Stress, mutators, mutations and stress resistance

Abstract

Organisms need genetic mechanisms to rapidly adapt to changing, stressful environments. Having a high mutation frequency would have a drag on a population due to the deleterious nature of mutations, but having a sub-population with high mutation rate due to the presence of mutator genes seems to be nature's solution. Far more is known about mutator genes in bacteria than in higher organisms. Mutator effects can be genetic, through mutations in genes that affect genome stability or it can be epigenetic through up-or down-regulation of these genes. The mutator genes can be genes with partially lost function, which deal with DNA replication or repair, or with detoxification of DNA-damaging cellular components. Transposons, which are sensitive to environmental stress, can also act as mutators in plants. Mutators can be constitutive or stress-induced. Most evidence for mutator-assisted evolution of stress resistance in plants is circumstantial, except for the evolution of atrazine herbicide resistance due to a nuclearly-inherited plastome mutator, which was repeated experimentally. An important feature of the mutator effect is that it is transient and is followed by reversion to the stable wild type, and can be counter-selected following outcrossing with the wild type. Similarly, remembered epigenetic stress-induced mutator effects were shown to last for a few generations. In summary, mutator genes could be playing an important role in the evolution of resistance to stress in plants, as it does in other systems, but to an extent that is yet unclear. © 2010 Springer Science + Business Media B.V. All Rights Reserved.