This Research Topic is part of the Epigenetic Modifications Associated with Abiotic and Biotic Stresses in Plants: An Implication for Understanding Plant Evolution series:
Epigenetic Modifications Associated with Abiotic and Biotic Stresses in Plants: An Implication for Understanding Plant EvolutionAlterations in gene expression are essential during growth and development phases and when plants are exposed to environmental challenges. Stress conditions induce gene expression modifications, which are associated with changes in the biochemical and physiological processes that help plants to avoid or reduce potential damage resulting from these stresses.
After exposure to stress, surviving plants tend to flower earlier than normal and therefore transfer the accumulated epigenetic information to their progenies, given that seeds, where this information is stored, are formed at a later stage of plant development.
DNA methylation is correlated with expression repression. Likewise, miRNA produced in the cell can reduce the transcript abundance or even prevent translation of mRNA. However, histone modulation, such as histone acetylation, methylation, and ubiquitination, can show distinct effects on gene expression. These alterations can be inherited, especially if the plants are consistently exposed to a particular environmental stress. Retrotransposons and retroviruses are foreign movable DNA elements that play an important role in plant evolution. Recent studies have shown that epigenetic alterations control the movement and the expression of genes harboured within these elements. These epigenetic modifications have an impact on the morphology, and biotic and abiotic tolerance in the subsequent generations because they can be inherited through the transgenerational memory in plants. Therefore, epigenetic modifications, including DNA methylation, histone modifications, and small RNA interference, serve not only to alter gene expression but also to enhance the evolutionary process in eukaryotes.
Epigenetic changes associated with gene evolution may describe the natural appearance of new varieties through a rapid evolutionary process. For a long time, scientists believed that various types of mutations within the DNA were the sole mechanism by which a new tolerant variety is naturally produced. At that time, epigenetic factors associated with developmental modifications and their impacts on DNA mutagenesis were not considered. However, recent findings have shown that prolonged exposure to stress conditions induces epigenetic changes leading to alterations in the chromosomal homologous recombination frequency (HRF) in somatic and possibly in sex cells, a process that may cause macromutation and produce new genes of novel function. Changes resulting from homologous recombination deviation under environmental stress selection are often stably inherited by subsequent generations. These changes can also speed up the adaptation process, which may take place over a longer time span if evolution depends only on random point mutations in the DNA.
The evolutionary history of plant species is usually measured based on the predicted DNA mutations regardless of the effects of epigenetic modifications on the HRF. Based on recent epigenetics discoveries, scientists are being forced to develop new bioinformatics tools that are able to consider epigenetic modifications in measuring the timeline of plant evolution based on the molecular clock.
In this Research Topic of Frontiers in Plant Science, we would like to encourage scientists to submit original research, opinion, innovative methodological approaches, and review articles that cover issues related to the role of DNA methylation, histone modifications, and small RNA in plant evolution through studying the effect of these modifications on gene expression, transgenerational memory, HRF, and stability of retrotransposons, retroviruses, and transgenes.