Genome size evolution is a process mainly determined by processes as polyploidization and amplification/loss of transposons, with a minor role played by other repeated sequences such as tandem repeats. In the cultivated olive, available data suggest a singular model of genome evolution, in which a massive expansion of tandem repeated sequences accompanied changes in nuclear architecture. Focusing on Olea genus evolution, NGS technologies, bioinformatics and in situ hybridization were applied to study the genome structure of 5 related Olea taxa originated at different times from the last common ancestor. On average, repetitive DNA in Olea taxa ranged from ~59% to ~73%, showing remarkable differences in terms of composition and abundance. We identified 11 major families of tandem repeats, 5 of which for the first time. Overall, tandem repeat abundance was inversely correlated to that of retrotransposons, with the exception of O. paniculata which has very few tandem-repeated sequences being, on the contrary, especially rich in long terminal repeat-retrotransposons, suggesting that the amplification of tandem repeats occurred after its divergence from the Olea common ancestor. Furthermore, cytological analyses underlined differences in genome size and chromatin organization of O. paniculata, whose genome is about 50% larger of that of cultivated olive compared to O. europaea subsp. europaea. Our results, supported by retrotransposon timing data and by in situ hybridization, indicates that the genome expansion of O. paniculata may be derived from massive amplification of major individual retrotransposon families in the last 20 MY. Our research identified the temporal dynamics shaping Olea genome structure, which represent a very peculiar model of evolution in higher plants characterized by a preminent role of tandem repeats in fostering genome structure variation, also suggesting a possible role of transposons in tandem repeats evolution and mobility.
The race between retrotransposons and tandem repeats for shaping genome structure. The case of Olea.
MASCAGNI F.;NATALI L.;BARGHINI E.;GIORDANI T.;CAVALLINI A.
2019-01-01
Abstract
Genome size evolution is a process mainly determined by processes as polyploidization and amplification/loss of transposons, with a minor role played by other repeated sequences such as tandem repeats. In the cultivated olive, available data suggest a singular model of genome evolution, in which a massive expansion of tandem repeated sequences accompanied changes in nuclear architecture. Focusing on Olea genus evolution, NGS technologies, bioinformatics and in situ hybridization were applied to study the genome structure of 5 related Olea taxa originated at different times from the last common ancestor. On average, repetitive DNA in Olea taxa ranged from ~59% to ~73%, showing remarkable differences in terms of composition and abundance. We identified 11 major families of tandem repeats, 5 of which for the first time. Overall, tandem repeat abundance was inversely correlated to that of retrotransposons, with the exception of O. paniculata which has very few tandem-repeated sequences being, on the contrary, especially rich in long terminal repeat-retrotransposons, suggesting that the amplification of tandem repeats occurred after its divergence from the Olea common ancestor. Furthermore, cytological analyses underlined differences in genome size and chromatin organization of O. paniculata, whose genome is about 50% larger of that of cultivated olive compared to O. europaea subsp. europaea. Our results, supported by retrotransposon timing data and by in situ hybridization, indicates that the genome expansion of O. paniculata may be derived from massive amplification of major individual retrotransposon families in the last 20 MY. Our research identified the temporal dynamics shaping Olea genome structure, which represent a very peculiar model of evolution in higher plants characterized by a preminent role of tandem repeats in fostering genome structure variation, also suggesting a possible role of transposons in tandem repeats evolution and mobility.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
