Project description:Evolution and adaptation of living organisms are results of permanent fights against diverse threats, which imply specific responses from the genome itself. Allopolyploidy, combining interspecific hybridization with whole genome duplication, is recognised as an important evolutionary force in plants. Its evolutionary success can be related to the rapid and profound genome reorganizations generated in response to the “Genome Shock” that allow the neo-allopolyploid to adapt efficiently to new environments. While work has focused on the structural and functional consequences of allopolyploidy, studies dedicated to the response of the neo-allopolyploid genome at the level of the functional regulation of genome expression have been rarely conducted. Recently, the hypothesis of a major role for small non coding RNAs (sRNAs) in mediating the immediate functional response of neo-allopolyploid genomes has progressively emerged. Here, we characterize the global response of sRNAs to allopolyploidy in Brassica, using three independent resynthesized B. napus allotetraploids surveyed at two different generations in comparison with their diploid progenitors, by high-throughput sequencing of sRNAs. Our evidence suggests an immediate but transient response of specific sRNA populations, targeting non-coding components of the genome. We identify the early accumulation of both 21- and 24-nt sRNAs involved in the regulation of the same targets, supporting a PTGS-to-TGS shift at the first stages of the neo-allopolyploid formation. We propose that sRNAs are early mobilized in response to allopolyploidy to control the unexpected transcriptional reactivation of various non-coding elements thus, playing the role of guardians of genome integrity during the first steps of neo-allopolyploid formation.
