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Satellite DNAs (SatDNA) are ubiquitously present in eukaryotic genomes and have been recently associated with several biological roles. Understanding the evolution and significance of SatDNA requires an extensive comparison across multiple phylogenetic depths. We combined the RepeatExplorer pipeline and cytogenetic approaches to conduct a comprehensive identification and analysis of the satellitome in 37 species from the genus Drosophila. We identified 188 SatDNA-like families, 112 of them being characterized for the first time. Repeat analysis within a phylogenetic framework has revealed the deeply divergent nature of SatDNA sequences in the Drosophila genus. The SatDNA content varied from 0.54% of the D. arizonae genome to 38.8% of the D. albomicans genome, with the SatDNA content often following a phylogenetic signal. Monomer size and guanine-cytosine-content also showed extreme variation ranging 2-570 bp and 9.1-71.4%, respectively. SatDNA families are shared among closely related species, consistent with the SatDNA library hypothesis. However, we uncovered the emergence of species-specific SatDNA families through amplification of unique or low abundant sequences in a lineage. Finally, we found that genome sizes of the Sophophora subgenus are positively correlated with transposable element content, whereas genome size in the Drosophila subgenus is positively correlated with SatDNA. This finding indicates genome size could be driven by different categories of repetitive elements in each subgenus. Altogether, we conducted the most comprehensive satellitome analysis in Drosophila from a phylogenetic perspective and generated the largest catalog of SatDNA sequences to date, enabling future discoveries in SatDNA evolution and Drosophila genome architecture.

Maria Luisa Somoza1 *, Natalia Pérez-Sánchez2 *, Isabel Torres-Rojas,1 Laura Martín-Pedraza,3 Natalia Blanca-López,1 Laura Victorio Puche,4 Eva Abel Fernández González,5 José Damián López Sánchez,6 Javier Fernández-Sánchez,7,8 Enrique Fernández-Caldas,5,9 Mayte Villalba,10 Francisco Javier Ruano,1 José Antonio Cornejo-García11 *, Gabriela Canto1,12 *, Miguel Blanca3 &#x002A1Allergy Department, Infanta Leonor University Hospital, Madrid, Spain; 2Allergy Department, Hospital Regional Universitario de Málaga, Málaga-IBIMA (FIMABIS), Málaga, Spain; 3Allergy Department, Fundación para la Investigación e Innovación Biomédica (FIIB) de los Hospitales Universitarios Infanta Leonor y Sureste, Madrid, Spain; 4Allergy Department, Morales Meseguer General University Hospital, Murcia, Spain; 5R&D Department, Inmunotek Laboratories, Madrid, Spain; 6Allergy Department, Virgen de la Arrixaca Clinical University Hospital, Murcia, Spain; 7Allergy Department, General University Hospital of Alicante- ISABIAL, Alicante, Spain; 8Clinical Medicine Department, Miguel Hernandez University, Alicante, Spain; 9Division of Allergy and Immunology, University of South Florida College of Medicine, Tampa, FL, USA; 10Department of Biochemistry and Molecular Biology, Universidad Complutense de Madrid, Madrid, Spain; 11Instituto de Investigación Biomédica de Málaga-IBIMA (FIMABIS), Málaga, Spain; 12School of Medicine, Universidad Complutense de Madrid, Madrid, Spain*These authors contributed equally to this workCorrespondence: Maria Luisa Somoza, Email mlsomoza@yahoo.comBackground: Allergy can start at early ages, with genetic and environmental factors contributing to its development.Aim: The study aimed to describe the pattern of sensitisation and allergy in children and adolescents of Spanish versus Moroccan ancestry but born in the same rural area of Spain.Methods: Participants were children and adolescents (3– 19 years) of

Show caves have different grades of colonization by phototrophic biofilms. They may receive a varied number of visits, from a few thousand to hundreds of thousands of visitors annually. Among them, Tesoro Cave, Rincon de la Victoria, Spain, showed severe anthropic alterations, including artificial lighting. The most noticeable effect of the lighting was the growth of a dense phototrophic community of cyanobacteria, algae and bryophytes on the speleothems, walls and ground. The biofilms were dominated by the cyanobacterium Phormidium sp., the chlorophyte Myrmecia israelensis, and the rhodophyte Cyanidium sp. In many cases, the biofilms also showed an abundance of the bryophyte Eucladium verticillatum. Other cyanobacteria observed in different biofilms along the cave were: Chroococcidiopsis sp., Synechocystis sp. and Nostoc cf. edaphicum, the green microalgae Pseudococcomyxa simplex, Chlorella sp. and the diatom Diadesmis contenta. Preliminary cleaning tests on selected areas showed the effectiveness of hydrogen peroxide and sodium hypochlorite. A physicochemical treatment involving the mechanical removal of the thickest layers of biofilms was followed by chemical treatments. In total, 94% of the surface was cleaned with hydrogen peroxide, with a subsequent treatment with sodium hypochlorite in only 1% of cases. The remaining 5% was cleaned with sodium hypochlorite in areas where the biofilms were entrapped into a calcite layer and in sandy surfaces with little physical compaction. The green biofilms from the entire cave were successfully cleaned.

The barcoding of the mitochondrial COX1 gene has been instrumental in cataloguing the tree of life, and in providing insights in the phylogeographic history of species. Yet, this strategy has encountered difficulties in major clades characterized by large genomes, which contain a high frequency of nuclear pseudogenes originating from the mitochondrial genome (numts). Here, we use the meadow grasshopper (Chorthippus parallelus), which possesses a giant genome of similar to 13 Gb, to identify mitochondrial genes that are underrepresented as numts, and test their use as informative phylogeographic markers. We recover the same full mitochondrial sequence using both whole genome and transcriptome sequencing, including functional protein-coding genes and tRNAs. We show that a region of the mitogenome containing the COX1 gene, typically used in DNA barcoding, has disproportionally higher diversity and coverage than the rest of the mitogenome, consistent with multiple insertions of that region into the nuclear genome. By designing new markers in regions of less elevated diversity and coverage, we identify two mitochondrial genes that are less likely to be duplicated as numts. We show that, while these markers show high levels of incomplete lineage sorting between subspecies, as expected for mitochondrial genes, genetic variation reflects their phylogeographic history accurately. These findings allow us to identify useful mitochondrial markers for future studies in C. parallelus, an important biological system for evolutionary biology. More generally, this study exemplifies how non-PCR-based methods using next-generation sequencing can be used to avoid numts in species characterized by large genomes, which have remained challenging to study in taxonomy and evolution.

Eukaryotic genomes contain large amounts of repetitive DNA sequences, such as tandemly repeated satelliteDNAs (satDNAs). These sequences are highly dynamic and tend to begenus- or species-specific due to their particular evolutionary pathways, although there are few unusual cases of conserved satDNAs over long periods of time. Here, we used multiple approaches to reveal that an satDNA named CharSat01-52 originated in the last common ancestor of Characoidei fish, a superfamily within the Characiformes order, similar to 140-78Ma, whereas its nucleotide composition has remained considerably conserved in several taxa. We show that 14 distantly related species within Characoidei share the presence of this satDNA, which is highly amplified and clustered in subtelomeric regions in a single species (Characidiumgomesi), while remained organized as small clusters in all the other species. Defying predictions of the molecular drive of satellite evolution, CharSat01-52 shows similar values of intra- and interspecific divergence. Although we did not provide evidence for a specific functional role of CharSat01-52, its transcriptional activity was demonstrated in different species. In addition, we identified short tandem arrays of CharSat01-52 embedded within single-molecule real-time long reads of Astyanax paranae (536 bp-3.1 kb) and A. mexicanus (501 bp-3.9 kb). Such arrays consisted of head-to-tail repeats and could b e found interspersed with other sequences, inverted sequences, or neighbored by other satellites. Our results provide a detailed characterization of an old and conserved satDNA, challenging general predictions of satDNA evolution.

Background: Eukaryote genomes frequently harbor supernumerary B chromosomes in addition to the "standard" A chromosome set. B chromosomes are thought to arise as byproducts of genome rearrangements and have mostly been considered intraspecific oddities. However, their evolutionary transcendence beyond species level has remained untested. Results: Here we reveal that the large metacentric B chromosomes reported in several fish species of the genus Astyanax arose in a common ancestor at least 4 million years ago. We generated transcriptomes of A. scabripinnis and A. paranae 0B and 1B individuals and used these assemblies as a reference for mapping all gDNA and RNA libraries to quantify coverage differences between B-lacking and B-carrying genomes. We show that the B chromosomes of A. scabripinnis and A. paranae share 19 protein-coding genes, of which 14 and 11 were also present in the B chromosomes of A. bockmanni and A. fasciatus, respectively. Our search for B-specific single-nucleotide polymorphisms (SNPs) identified the presence of B-derived transcripts in B-carrying ovaries, 80% of which belonged to nobox, a gene involved in oogenesis regulation. Importantly, the B chromosome nobox paralog is expressed >30x more than the A chromosome paralog. This indicates that the normal regulation of this gene is altered in B-carrying females, which could potentially facilitate B inheritance at higher rates than Mendelian law prediction. Conclusions: Taken together, our results demonstrate the long-term survival of B chromosomes despite their lack of regular pairing and segregation during meiosis and that they can endure episodes of population divergence leading to species formation.