Genome最新文献

Ticks transmit pathogens of veterinary and public health importance. Understanding their diversity is critical as infestations lead to significant economic losses globally. To date, over 90 species across three families have been identified in South Africa. However, the taxonomy of most species has not been resolved due to morphological identification challenges. DNA barcoding through the Barcode of Life Data Systems (BOLD) is therefore a valuable tool for species verifications for biodiversity assessments. This study conducted an analysis of South African tick COI barcodes on BOLD by verifying species on checklists, literature, and other sequence databases. The compiled list represented 97 species, including indigenous (59), endemics (27), introduced (2), invasives (1), and eight that could not be classified. Analyses indicated that 31 species (32%) from 11 genera have verified COI barcodes. These are distributed across all nine provinces with the Eastern Cape having the highest species diversity, followed by Limpopo, with KwaZulu-Natal having the least diversity. Rhipicephalus, Hyalomma, and Argas species had multiple barcode index numbers, suggesting cryptic diversity or unresolved taxonomy. We identified 21 species of veterinary or zoonotic importance from the Argasidae and Ixodidae families that should be prioritised for barcoding. Coordinating studies and defining barcoding targets is necessary to ensure that tick checklists are updated to support decision-making for the control of vector-borne diseases and alien invasives.

β-Caryophyllene possesses potential anticancer properties against various cancers, including breast, colon, and lung cancer. Therefore, the essential oil of Ayapana triplinervis, which is rich in β-caryophyllene, can be a potential herbal remedy for treating cancer. However, molecular and genomic studies on A. triplinervis are still sparse. In this study, we obtained 14.7 Gb of RNA-Seq data from A. triplinervis leaf RNA and assembled 1,37,554 transcripts with an N50 value of 1,437 bp. We annotated 72,436 (52.7%) transcripts and mapped 10,640 transcripts to 156 biochemical pathways. Among them, 218 were related to terpenoid backbone biosynthesis, while 27 were linked to sesquiterpenoid and triterpenoid pathways. Ninety-four transcripts were annotated in the β-caryophyllene and lupeol pathways. From these transcripts, for the first time, we identified 25 full-length genes encoding all the 17 enzymes involved in β-caryophyllene biosynthesis and an additional five genes involved in lupeol biosynthesis. These genes will be useful for the metabolic engineering of β-caryophyllene and lupeol biosynthesis, not just in A. triplinervis but also in other species. Keywords: β-caryophyllene, Eupatorium ayapana, Eupatorium triplinervis, lupeol, transcriptome.

Combating wildlife crimes in South Africa requires accurate identification of traded species and their products. Diagnostic morphological characteristics needed to identify species are often lost when specimens are processed and customs officials lack the expertise to identify species. As a potential solution, DNA barcoding can be used to identify morphologically indistinguishable specimens in forensic cases. However, barcoding is hindered by the reliance on comprehensive, validated DNA barcode reference databases, which are currently limited. To overcome this limitation, we constructed a barcode library of cytochrome c oxidase subunit 1 and cytochrome b sequences for threatened and protected mammals exploited in southern Africa. Additionally, we included closely related or morphologically similar species and assessed the database's ability to identify species accurately. Published southern African sequences were incorporated to estimate intraspecific and interspecific variation. Neighbor-joining trees successfully discriminated 94%-95% of the taxa. However, some widespread species exhibited high intraspecific distances (>2%), suggesting geographic sub-structuring or cryptic speciation. Lack of reliable published data prevented the unambiguous discrimination of certain species. This study highlights the efficacy of DNA barcoding in species identification, particularly for forensic applications. It also highlights the need for a taxonomic re-evaluation of certain widespread species and challenging genera.

The genome organization of woodpeckers has several distinctive features e.g., an uncommon accumulation of repetitive sequences, enlarged Z chromosomes, and atypical diploid numbers. Despite the large diversity of species, there is a paucity of detailed cytogenomic studies for this group and we thus aimed to rectify this. Genome organization patterns and hence evolutionary change in the microchromosome formation of four species (Colaptes campestris, Veniliornis spilogaster, Melanerpes candidus, and Picumnus nebulosus) was established through fluorescence in situ hybridization using bacterial artificial chromosomes originally derived from Gallus gallus and Taeniopygia guttata. Findings suggest that P. nebulosus (2n = 110), which was described for the first time, had the most basal karyotype among species of Picidae studied here, and probably arose as a result of fissions of avian ancestral macrochromosomes. We defined a new chromosomal number for V. spilogaster (2n = 88) and demonstrated microchromosomal rearrangements involving C. campestris plus a single, unique hitherto undescribed rearrangement in V. spilogaster. This comprised an inversion after a fusion involving the ancestral microchromosome 12 (homologous to chicken microchromosome 12). We also determined that the low diploid number of M. candidus is related to microchromosome fusions. Woodpeckers thus exhibit significantly rearranged karyotypes compared to the putative ancestral karyotype.

Advances in sequencing technology allow whole plant genomes to be sequenced with high quality. Combining genotypic and phenotypic data in genomic prediction helps breeders to select crossing partners in partially phenotyped populations. In plant breeding programs, the cost of sequencing entire breeding populations still exceeds available genotyping budgets. Hence, the method for genotyping is still mainly single nucleotide polymorphism (SNP) arrays; however, arrays are unable to assess the entire genome- and population-wide diversity. A compromise involves genotyping the entire population using an SNP array and a subset of the population with whole-genome sequencing. Both datasets can then be used to impute markers from whole-genome sequencing onto the entire population. Here, we evaluate whether imputation of whole-genome sequencing data enhances genomic predictions, using data from a nested association mapping population of rapeseed (Brassica napus). Employing two cross-validation schemes that mimic scenarios for the prediction of close and distant relatives, we show that imputed marker data do not significantly improve prediction accuracy, likely due to redundancy in relationship estimates and imputation errors. In simulation studies, only small improvements were observed, further corroborating the findings. We conclude that SNP arrays are already equipped with the information that is added by imputation through relationship and linkage disequilibrium.

The Cuculiformes are a family of over 150 species that live in a range of habitats, such as forests, savannas, and deserts. Here, bacterial artificial chromosome (BAC) probes (75 from chicken and 14 from zebra finch macrochromosomes 1-10 +ZW and for microchromosomes 11-28 (except 16)) were used to investigate chromosome homologies between chicken and the squirrel cuckoo (Piaya cayana). In addition, repetitive DNA probes were applied to characterize the chromosome organization and to explore the role of these sequences in the karyotype evolution of P. cayana. We also applied BAC probes for chicken chromosome 17 and Z to the guira cuckoo (Guira guira) to test whether this species has an unusual Robertsonian translocation between a microchromosome and the Z chromosome, recently described in the smooth-billed ani (Crotophaga ani). Our results revealed extensive chromosome reorganization with inter- and intrachromosomal rearrangements in P. cayana, including a conspicuous chromosome size and heterochromatin polymorphism on chromosome pair 20. Furthermore, we confirmed that the Z-autosome Robertsonian translocation found in C. ani is also found in G. guira, not P. cayana. These findings suggest that this translocation occurred prior to the divergence between C. ani and G. guira, but after the divergence with P. cayana.

Campylobacter infections are a leading cause of bacterial diarrheal illness worldwide, with increasing reports of outbreaks in both developing and developed countries. Most studies investigating strain genotypes and epidemiology of Campylobacter jejuni examined on a local scale. Using the archived multilocus sequence typing data at seven loci, and associated strain metadata from the PubMLST database, here we investigated the spatial and temporal genetic structure of the global population of C. jejuni. Our analyses revealed evidence for clonal dispersals of multiple sequence types (STs) among countries and continents. However, despite the observed clonal dispersal and that most genetic variations were found within individual geographic subpopulations, both the non-clone-corrected and clone-corrected samples showed evidence of significant genetic differentiation among national and continental subpopulations, with non-clone-corrected samples showing greater differentiation than clone-corrected samples. Phylogenetic incompatibility analyses provided evidence for recombination within each continental subpopulation. However, linkage disequilibrium analyses rejected the hypothesis of random recombination across the samples. Temporally, multiple STs were found to persist across four decades and the five globally most common STs showed relatively stable frequencies over the last two decades. We discussed the implications of our results to food security, disease transmission, and public health management.

For peanut, the lack of stable cytological markers is a barrier to tracking specific chromosomes, elucidating the genetic relationships between genomes and identifying chromosomal variations. Chromosome mapping using single-copy oligonucleotide (oligo) probe libraries has unique advantages for identifying homologous chromosomes and chromosomal rearrangements. In this study, we developed two whole-chromosome single-copy oligo probe libraries, LS-7A and LS-8A, based on the reference genome sequences of chromosomes 7A and 8A of Arachis duranensis. Fluorescence in situ hybridization (FISH) analysis confirmed that the libraries could specifically paint chromosomes 7 and 8. In addition, sequential FISH and electronic localization of LS-7A and LS-8A in A. duranensis (AA) and A. ipaensis (BB) showed that chromosomes 7A and 8A contained translocations and inversions relative to chromosomes 7B and 8B. Analysis of the chromosomes of wild Arachis species using LS-8A confirmed that this library could accurately and effectively identify A genome species. Finally, LS-7A and LS-8A were used to paint the chromosomes of interspecific hybrids and their progenies, which verified the authenticity of the interspecific hybrids and identified a disomic addition line. This study provides a model for developing specific oligo probes to identify the structural variations of other chromosomes in Arachis and demonstrates the practical utility of LS-7A and LS-8A.

Mycoplasmopsis bovis is a worldwide economically important pathogen of cattle that can cause or indirectly contribute to bovine respiratory disease. M. bovis is also a primary etiological agent of respiratory disease in bison with high mortality rates. A major challenge in the development of an efficacious M. bovis vaccine is the design of antigens that contain both MHC-1 and MHC-2 T-cell epitopes, and that account for population level diversity within the species. Publicly available genomes and sequence read archive libraries of 381 M. bovis strains isolated from cattle (n = 202) and bison (n = 179) in North America were used to identify a core genome of 575 genes, including 38 that encode either known or predicted secreted or outer membrane proteins. The antigenic potentials of the proteins were characterized by the presence and strength of their T-cell epitopes, and their protein variant diversity at the population-level. The proteins had surprisingly low diversity and varying predictive levels of T-cell antigenicity. These results provide a reference for the selection or design of antigens for vaccine testing against strains infecting North American cattle and bison.

The last decade has been highlighted by the increased use of next-generation DNA sequencing technology to identify novel human disease genes. A critical downstream part of this process is assigning function to a candidate gene variant. Functional studies in Drosophila melanogaster, the common fruit fly, have made a prominent contribution in annotating variant impact in an in vivo system. The use of patient-derived knock-in flies or rescue-based, "humanization", approaches are novel and valuable strategies in variant testing but have been recently widely reviewed. An often-overlooked strategy for determining variant impact has been GAL4/upstream activation sequence-mediated tissue-defined overexpression in Drosophila. This mini-review will summarize the recent contribution of ectopic overexpression of human reference and variant cDNA in Drosophila to assess variant function, interpret the consequence of the variant, and in some cases infer biological mechanisms.