145473 20260217205603.0 doi 10.1186/s12870-024-05658-5 sideral 140319 ART-2024-140319 eng Trunova, Dana Does time matter? Intraspecific diversity of ribosomal RNA genes in lineages of the allopolyploid model grass Brachypodium hybridum with different evolutionary ages 2024 Access copy available to the general public Unrestricted Background Polyploidisation often results in genome rearrangements that may involve changes in both the single-copy sequences and the repetitive genome fraction. In this study, we performed a comprehensive comparative analysis of repetitive DNA, with a particular focus on ribosomal DNA (rDNA), in Brachypodium hybridum (2n = 4x = 30, subgenome composition DDSS), an allotetraploid resulting from a natural cross between two diploid species that resemble the modern B. distachyon (2n = 10; DD) and B. stacei (2n = 20; SS). Taking advantage of the recurrent origin of B. hybridum, we investigated two genotypes, Bhyb26 and ABR113, differing markedly in their evolutionary age (1.4 and 0.14 Mya, respectively) and which resulted from opposite cross directions. To identify the origin of rDNA loci we employed cytogenetic and molecular methods (FISH, gCAPS and Southern hybridisation), phylogenetic and genomic approaches. Results Unlike the general maintenance of doubled gene dosage in B. hybridum, the rRNA genes showed a remarkable tendency towards diploidisation at both locus and unit levels. While the partial elimination of 35S rDNA units occurred in the younger ABR113 lineage, unidirectional elimination of the entire locus was observed in the older Bhyb26 lineage. Additionally, a novel 5S rDNA family was amplified in Bhyb26 replacing the parental units. The 35S and 5S rDNA units were preferentially eliminated from the S- and D-subgenome, respectively. Thus, in the more ancient B. hybridum lineage, Bhyb26, 5S and 35S rRNA genes are likely expressed from different subgenomes, highlighting the complexity of polyploid regulatory networks. Conclusion Comparative analyses between two B. hybridum lineages of distinct evolutionary ages revealed that although the recent lineage ABR113 exhibited an additive pattern of rDNA loci distribution, the ancient lineage Bhyb26 demonstrated a pronounced tendency toward diploidisation manifested by the reduction in the number of both 35S and 5S loci. In conclusion, the age of the allopolyploid appears to be a decisive factor in rDNA turnover in B. hybridum. info:eu-repo/grantAgreement/ES/MICINN/PID2022-140074NB-I00 info:eu-repo/grantAgreement/EUR/MICINN/TED2021-131073B-I00 info:eu-repo/semantics/openAccess by https://creativecommons.org/licenses/by/4.0/deed.es 4.8 2024 PLANT SCIENCES 33 / 273 = 0.121 2024 Q1 T1 1.134 2024 Plant Science 2024 Q1 6.7 2024 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Borowska-Zuchowska, Natalia Mykhailyk, Serhii Xia, Kai Zhu, Yuanbin Sancho, Ruben Rojek-Jelonek, Magdalena Garcia, Sònia Wang, Kai Catalan, Pilar Universidad de Zaragoza (orcid)0000-0001-7793-5259 Kovarik, Ales Hasterok, Robert Kolano, Bozena 5011 063 Universidad de Zaragoza Dpto. CC.Agrar.y Medio Natural Área Botánica 24, 1 (2024), 981 [14 p.] BMC PLANT BIOLOGY BMC PLANT BIOLOGY 1471-2229 5370123 http://zaguan.unizar.es/record/145473/files/texto_completo.pdf Versión publicada 2103843 http://zaguan.unizar.es/record/145473/files/texto_completo.jpg?subformat=icon icon Versión publicada oai:zaguan.unizar.es:145473 articulos driver 2026-02-17-20:45:33 ARTICLE