Activation of Plant LTR-retrotransposons under in Vitro Culture Stress

Retrotransposons make up a significant part of plant genome and are probably the most dynamic part of it, so they play a significant role in the generation of genetic variation. In particular, their activation can lead to structural reorganization of genome and changes in genome size, the emergence of novel genetic and phenotypic variants, as well as changes in gene expression, thus providing the raw material for adaptation and evolution. This review summarizes literature data on the activation of LTR-retrotransposons of the superfamilies Ty1/Copia and Ty3/Gypsy during in vitro culture and under various abiotic and biotic stress conditions. Their structure, classification, and significance for the organization and functioning of plant genome are reviewed. The main mechanisms of activation of LTR-retrotransposons under stress conditions are explored, including changes in DNA methylation and interaction of stress-induced transcription factors with retrotransposon promoters due to the presence of specific binding sites and other regulatory elements. The review also discusses consequences of activation of retrotransposons and control of their activity by self-inactivation mechanisms and the epigenetic regulation of genome.Keywords: retrotransposons, Ty1/Copia, Ty3/Gypsy, in vitro culture, abiotic and biotic stress.