RESUMO
The Przewalski's horse (Equus ferus przewalskii) is an endangered equid native to the steppes of central Asia. After becoming extinct in the wild multiple conservation efforts convened to preserve the species, including captive breeding programs, reintroduction and monitoring systems, protected lands, and cloning. Availability of a highly contiguous reference genome is essential to support these continued efforts. We used Oxford Nanopore sequencing to produce a scaffold-level 2.5 Gb nuclear assembly and 16,002 bp mitogenome from a captive Przewalski's mare. All assembly drafts were generated from 111 Gb of sequence from a single PromethION R10.4.1 flow cell. The mitogenome contained 37 genes in the standard mammalian configuration and was 99.63% identical to the domestic horse (Equus caballus). The nuclear assembly, EquPr2, contained 2,146 scaffolds with an N50 of 85.1 Mb, 43X mean depth, and BUSCO quality score of 98.92%. EquPr2 successfully improves upon the existing Przewalski's horse reference genome (Burgud), with 25-fold fewer scaffolds, a 166-fold larger N50, and phased pseudohaplotypes. Modified basecalls revealed 79.5% DNA methylation and 2.1% hydroxymethylation globally. Allele-specific methylation analysis between pseudohaplotypes revealed 226 differentially methylated regions (DMRs) in known imprinted genes and loci not previously reported as imprinted. The heterozygosity rate of 0.165% matches previous estimates for the species and compares favorably to other endangered animals. This improved Przewalski's horse assembly will serve as a valuable resource for conservation efforts and comparative genomics investigations.
RESUMO
The Przewalski's horse (Equus ferus przewalskii) is an endangered equid native to the steppes of central Asia. After becoming extinct in the wild, multiple conservation efforts convened to preserve the species including captive breeding programs, reintroduction and monitoring systems, protected lands, and cloning. Availability of a highly contiguous reference genome is essential to support these continued efforts. We used Oxford Nanopore sequencing to produce a scaffold-level 2.5 Gb nuclear assembly and 16,002 bp mitogenome from a captive Przewalski's mare. All assembly drafts were generated from 111 Gb of sequence from a single PromethION R10.4.1 flow cell. The mitogenome contained 37 genes in the standard mammalian configuration and was 99.63% identical to the domestic horse (Equus caballus). The nuclear assembly, EquPr2, contained 2,146 scaffolds with an N50 of 85.1 Mb, 43X mean depth, and BUSCO quality score of 98.92%. EquPr2 successfully improves upon the existing Przewalski's horse reference genome (Burgud), with 25-fold fewer scaffolds, a 166-fold larger N50, and phased pseudohaplotypes. Modified basecalls revealed 79.5% DNA methylation and 2.1% hydroxymethylation globally. Allele-specific methylation analysis between pseudohaplotypes revealed 226 differentially methylated regions (DMRs) in known imprinted genes and loci not previously reported as imprinted. The heterozygosity rate of 0.165% matches previous estimates for the species and compares favorably to other endangered animals. This improved Przewalski's horse assembly will serve as a valuable resource for conservation efforts and comparative genomics investigations.
RESUMO
Research on the public health significance of Ixodes scapularis ticks in the Midwest seldom focuses on extreme weather conditions that can modulate their population dynamics and ability to transmit pathogenic organisms. In this study, we assessed whether the distributional abundance of I. scapularis immatures is associated with current and time-lagged climatic determinants either directly or indirectly. We analyzed a 20-year longitudinal small mammal live-trapping dataset within a seven-county metropolitan area in Minnesota (1998-2016) using yearly tick counts at each site to assess whether inter- and intra-annual variation in immature I. scapularis counts is associated with climate and land-use conditions. We found that (1) immature I. scapularis ticks infesting mammals expanded southwesterly over the study period, (2) eastern chipmunks, Tamias striatus, supplied a substantial proportion of nymphal blood meals, (3) a suite of climatological variables are demonstrably associated with I. scapularis presence, and abundance across sites, most notably summer vapor pressure deficit, and (4) immature I. scapularis display an affinity for deciduous forests in metro areas. Our results suggest that climatic and land-type conditions may impact host-seeking I. scapularis ticks through numerous mechanistic avenues. These findings extend our understanding of the abiotic factors supporting I. scapularis populations in metro areas of the upper Midwest with strong implications for discerning future tick-borne pathogen risk.
