Assessing the impact of USER-treatment on hyRAD capture applied to ancient DNA.

Ancient DNA preservation in subfossil specimens provides a unique opportunity to retrieve genetic information from the past. As ancient DNA extracts are generally dominated by molecules originating from environmental microbes, capture techniques are often used to economically retrieve orthologous sequence data at the population scale. Post-mortem DNA damage, especially the deamination of cytosine residues into uracils, also considerably inflates sequence error rates unless ancient DNA extracts are treated with the USER enzymatic mix prior to library construction. While both approaches have recently gained popularity in ancient DNA research, the impact of USER-treatment on capture efficacy still remains untested. In this study, we applied hyRAD capture to eight ancient equine subfossil specimens from France (1st-17th century CE), including horses, donkeys and their first-generation mule hybrids. We found that USER-treatment could reduce capture efficacy and introduce significant experimental bias. It differentially affected the size distribution of on-target templates following capture with two distinct hyRAD probe sets in a manner that was not driven by differences in probe sizes and DNA methylation levels. Finally, we recovered unbalanced proportions of donkey-specific and horse-specific alleles in mule capture sequence data, due to the combined effects of USER-treatment, probe sets and reference bias. Our work demonstrates that while USER-treatment can improve the quality of ancient DNA sequence data, it can also significantly affect hyRAD capture outcomes, introducing bias in the sequence data that is difficult to predict based on simple molecular probe features. Such technical batch effects may prove easier to model and correct for using capture with synthetic probes of controlled sizes and diversity content.

Genome assembly and annotation of Meloidogyne enterolobii, an emerging parthenogenetic root-knot nematode.

Root-knot nematodes (genus Meloidogyne) are plant parasites causing huge economic loss in the agricultural industry and affecting severely numerous developing countries. Control methods against these plant pests are sparse, the preferred one being the deployment of plant cultivars bearing resistance genes against Meloidogyne species. However, M. enterolobii is not controlled by the resistance genes deployed in the crop plants cultivated in Europe. The recent identification of this species in Europe is thus a major concern. Here, we sequenced the genome of M. enterolobii using short and long-read technologies. The genome assembly spans 240 Mbp with contig N50 size of 143 kbp, enabling high-quality annotations of 59,773 coding genes, 4,068 non-coding genes, and 10,944 transposable elements (spanning 8.7% of the genome). We validated the genome size by flow cytometry and the structure, quality and completeness by bioinformatics metrics. This ensemble of resources will fuel future projects aiming at pinpointing the genome singularities, the origin, diversity, and adaptive potential of this emerging plant pest.

Author Correction: Genome assembly and annotation of Meloidogyne enterolobii, an emerging parthenogenetic root-knot nematode.

A Correction to this paper has been published: https://doi.org/10.1038/s41597-020-00747-0.