The role of siRNAs in genome stability maintaining in the bread wheat introgression lines

Aim. Deviations of the siRNAs levels from the parental ones in the plants with hybrid genomes are associated with the activation of transposable elements (TE). This, in turn, lead to the further genome rearrangements. Introgression lines Triticum aestivum / Amblyopyrum muticum are cytologically stable, however, there are visible signs of genetic and (or) epigenetic restructuring that are still going on. Molecular mechanisms of these processes are the subject of our study. Methods. The levels of siRNAs in the plant lemmas were determined by small RNA-seq. Reads of the small RNA libraries were aligned to the repeats to find siRNA sequences. Results. Introgression lines (ILs) and parental amphidiploid have variable levels of siRNAs regulating MITE and CACTA transposable elements, compared with the parental bread wheat variety. For twelve TE sequences, majority of which are CACTA elements, decrease in the levels of siRNAs in ILs and amphidiploid, compared to the wheat, is statistically significant. Decreased siRNAs levels could lead to the activation of corresponding TE classes. Conclusions. Variation of siRNA levels in ILs and amphidiploid can be the key factor that cause rearrangements in their genomes. These include activation of TEs, changes in DNA methylation patterns, and gene expression variation. Therefore, detected changes in siRNA levels can be the molecular mechanisms of the processes that occur in studied hybrid genomes. Keywords: siRNA, transposable elements, amphidiploid, introgression lines.