Impacto de hibridação interespecífica e poliploidização na fração repetitiva de genótipos de Paspalum (grupo Plicatula)

Abstract

In this study, we investigated the repeatome of P. compressifolium and P. lenticulare (Plicatula group), which include sexual diploid and apomictic tetraploid cytotypes, as well as their reciprocal diploid hybrids (H10 and H56) and the hybrids H77 (fertile) and H89 (sterile), obtained by artificial tetraploidization of H56. Analyses were performed using low-coverage genomic sequencing data (1-5x), with identification and classification of transposable elements and satellite sequences through the RepeatExplorer/TAREAN pipeline. The total repetitive fraction was relatively stable (45-50%), with a predominance of Class I retrotransposons. The SIRE lineage represented the most consistent component (16-20%), whereas lineages within the Ty3-Gypsy superfamily exhibited directional remodeling, including expansion of Retand in the diploid hybrids and reduction of Tekay in the sterile hybrid H89. Class II elements remained a minor component, dominated by EnSpm/CACTA, in proportions similar to those reported for other Panicoideae. Satellite DNA families displayed greater plasticity, with patterns of amplification, reduction, loss, and exclusivity among genotypes. Species- and cytotype-specific satellite sequences were identified in P. compressifolium and P. lenticulare, including families restricted to diploids or tetraploids. In the reciprocal diploid hybrids, asymmetric retention and expansion of families were observed: PpSat2 and PpSat7 were amplified in H10, whereas PpSat3 and PpSat4 expanded in H56. Some families were amplified in only one hybrid (PpSat5 in H10; PpSat8 and PpSat14 in H56), indicating directional effects of hybridization. Among the tetraploidized hybrids, H77 retained and amplified a broader satellite repertoire, whereas H89 exhibited losses and reductions. Overall, the results show that although the global repeatome of Paspalum maintains quantitative stability, satellite DNAs respond dynamically to hybridization and polyploidization through amplification, reduction, loss, and lineage-specific retention. These findings are consistent with the “library” hypothesis of satellite DNA. The combination of conserved families alongside asymmetric retention or loss of others indicates that distinct evolutionary processes including differential amplification, preferential elimination, and genetic drift have acted unevenly across parental lineages and ploidy levels. The resulting patterns reflect the cumulative action of these mechanisms in reshaping the satellitome and provide a framework for comparative cytogenomic interpretations and for applications in forage grass breeding.