Naranjo-Ortiz, M. A. | Search bioRxiv

bioRxiv2021

Karyon: a computational framework for the diagnosis of hybrids, aneuploids, and other non-standard architectures in genome assemblies.

Recent technological developments have made genome sequencing and assembly accessible to many groups. However, the presence in sequenced organisms of certain genomic features such as high heterozygosity, polyploidy, aneuploidy, or heterokaryosis can challenge current standard assembly procedures and result in highly fragmented assemblies. Hence, we hypothesized that genome databases must contain a non-negligible fraction of low-quality assemblies that result from such type of intrinsic genomic factors. Here we present Karyon, a Python-based toolkit that uses raw sequencing data and de novo genome assembly to assess several parameters and generate informative plots to assist in the identification of non-chanonical genomic traits. Karyon includes automated de novo genome assembly and variant calling pipelines. We tested Karyon by diagnosing 35 highly fragmented publicly available assemblies from 19 different Mucorales (Fungi) species. Our results show that 6 (17%) of the assemblies presented signs of unusual genomic configurations, suggesting that these are common, at least within the Fungi.

genomics↗

bioRxiv2019

Massive gene presence/absence variation in the mussel genome as an adaptive strategy: first evidence of a pan-genome in Metazoa

Mussels are ecologically and economically relevant edible marine bivalves, highly invasive and resilient to biotic and abiotic stressors causing recurrent massive mortalities in other species. Here we show that the Mediterranean mussel Mytilus galloprovincialis has a complex pan-genomic architecture, which includes a core set of 45,000 genes shared by all individuals plus a surprisingly high number of dispensable genes ([~]15,000). The latter are subject to presence/absence variation (PAV), i.e., they may be entirely missing in a given individual and, when present, they are frequently found as a single copy. The enrichment of dispensable genes in survival functions suggests an adaptive value for PAV, which might be the key to explain the extraordinary capabilities of adaptation and invasiveness of this species. Our study underpins a unique metazoan pan-genome architecture only previously described in prokaryotes and in a few non-metazoan eukaryotes, but that might also characterize other marine invertebrates.\n\nSignificance statementIn animals, intraspecific genomic diversity is generally thought to derive from relatively small-scale variants, such as single nucleotide polymorphisms, small indels, duplications, inversions and translocations. On the other hand, large-scale structural variations which involve the loss of genomic regions encoding protein-coding genes in some individuals (i.e. presence/absence variation, PAV) have been so far only described in bacteria and, occasionally, in plants and fungi. Here we report the first evidence of a pan-genome in the animal kingdom, revealing that 25% of the genes of the Mediterranean mussel are subject to PAV. We show that this unique feature might have an adaptive value, due to the involvement of dispensable genes in functions related with defense and survival.

genetics↗