Genome最新文献

Eleocharis R. Br. (Cyperaceae) species are known for having holocentric chromosomes, which enable rapid karyotype differentiation. High intra- and interspecific variations in chromosome numbers and genome sizes are documented for different Eleocharis species, frequently accompanied by fluctuations in the repetitive DNA fraction. However, a lack of detailed analysis has hampered a better understanding of the interplay between holocentricity and repetitive DNA evolution in this genus. In our study, we confirmed the holocentricity of Eleocharis chromosomes by immunostaining against the kinetochore protein KNL1 and the cell-cycle dependent posttranslational modifications histone H2AThr121ph and H3S10ph. We further studied the composition and chromosomal distribution of the main satellite DNA repeats found in the newly sequenced species Eleocharis maculosa, Eleocharis geniculata, Eleocharis parodii, Eleocharis elegans, and Eleocharis montana. Five of the six satellites discovered were arranged in clusters, while EmaSAT14 was distributed irregularly along the chromatid length in a line-like manner. EmaSAT14 monomers were present in a few copies in few species across the Eleocharis phylogenetic tree. Nonetheless, they were accumulated within a restricted group of Maculosae series, subgenus Eleocharis. The data indicates that the amplification and line-like distribution of EmaSAT14 along chromatids may have occurred recently within a section of the genus.

Recombination, the reciprocal exchange of DNA between homologous chromosomes, is a mandatory step necessary for meiosis progression. Crossovers between homologous chromosomes generate new combinations of alleles and maintain genetic diversity. Due to genetic, epigenetic, and environmental factors, the recombination landscape is highly heterogeneous along the chromosomes and it also differs between populations and between sexes. Here, we investigated recombination characteristics across the 19 chromosomes of the model allopolyploid crop species oilseed rape (Brassica napus L.), using two unique multiparental populations derived from two genetically divergent founder pools, each of which comprised 50 genetically diverse founder accessions. A fully balanced, pairwise chain-crossing scheme was utilized to create each of the two populations. A total of 3213 individuals, spanning five successive generations, were genotyped using a 15K SNP array. We observed uneven distribution of recombination along chromosomes, with some genomic regions undergoing substantially more frequent recombination in both populations. In both populations, maternal recombination events were more frequent than paternal recombination. This study provides unique insight into the recombination landscape at chromosomal level and reveals a maternal-paternal bias for recombination number with implications for breeding.

Brassica napus L. plants are sensitive to water stress conditions throughout their life cycle from seed germination to seed setting. This study aims at identifying quantitative trait loci (QTL) linked to B. napus tolerance to water stress mimicked by applications of 10% polyethylene glycol-6000 (PEG-6000). Two doubled haploid populations, each consisting of 150 genotypes, were used for this research. Plants at the two true leaf stage of development were grown in the absence (control) or presence (stress) of PEG-6000 under controlled environmental conditions for 48 h, and the drought stress index was calculated for each genotype. All genotypes, along with their parents, were genotyped using the Brassica Infinium 90K SNP BeadChip Array. Inclusive composite interval mapping was used to identify QTL. Six QTL and 12 putative QTL associated with water stress tolerance were identified across six chromosomes (A2, A3, A4, A9, C3, and C7). Collectively, 2154 candidate genes for water stress tolerance were identified for all the identified QTL. Among them, 213 genes were identified as being directly associated with water stress (imposed by PEG-6000) tolerance based on nine functional annotations. These results can be incorporated into future breeding initiatives to select plant material with the ability to cope effectively with water stress.

Heat stress affects the growth and development of Brassicaceae crops. Plant breeders aim to mitigate the effects of heat stress by selecting for heat stress tolerance, but the genes responsible for heat stress in Brassicaceae remain largely unknown. During heat stress, heat shock proteins (HSPs) function as molecular chaperones to aid in protein folding, and heat shock transcription factors (HSFs) serve as transcriptional regulators of HSP expression. We identified 5002 heat shock related genes, including HSPs and HSFs, across 32 genomes in Brassicaceae. Among these, 3347 genes were duplicated, with segmented duplication primarily contributing to their expansion. We identified 466 physical gene clusters, including 240 homogenous clusters and 226 heterogeneous clusters, shedding light on the organization of heat shock related genes. Notably, 37 genes were co-located with published thermotolerance quantitative trait loci, which supports their functional role in conferring heat stress tolerance. This study provides a comprehensive resource for the identification of functional Brassicaceae heat shock related genes, elucidates their clustering and duplication patterns and establishes the genomic foundation for future heat tolerance research. We hypothesise that genetic variants in HSP and HSF genes in certain species have potential for improving heat stress tolerance in Brassicaceae crops.

Key message We mapped 11 sorghum traits, identified 33 candidate genes, and found a grain yield gene (GID1) that regulates seed development and a grass-specific tillering gene (DUF1618) transferred to Striga hermonthica.

Mitochondrial DNA is commonly used in population genetic studies to investigate spatial structure, intraspecific variation, and phylogenetic relationships. The control region is the most rapidly evolving and largest non-coding region, but its analysis can be complicated by heteroplasmic signals of genome duplication in many mammals, including felids. Here, we describe the presence of heteroplasmy in the control region of Canada lynx (Lynx canadensis) through intra-individual sequence variation. Our results demonstrate multiple haplotypes of varying length in each lynx, resulting from different copy numbers of the repetitive sequence RS-2 and suggest possible heteroplasmic single nucleotide polymorphisms in both repetitive sequences RS-2 and RS-3. Intra-individual variation was only observed in the repetitive sequences while inter-individual variation was detected in the flanking regions outside of the repetitive sequences, indicating that heteroplasmic mutations are restricted to these repeat regions. Although each lynx displayed multiple haplotypes of varying length, we found the most common variant contained three complete copies of the RS-2 repeat unit, suggesting copy number is regulated by stabilizing selection. While genome duplication offers potential for increased diversity, heteroplasmy may lead to a selective advantage or detriment in the face of mitochondrial function and disease, which could have significant implications for wildlife populations experiencing decline (e.g., bottlenecks) as a result of habitat modification or climate change.

We unified the recent literature with the goal to contribute to the discussion on how genetic diversity might best be conserved. We argue that this decision will be guided by how genomic variation is distributed among manageable populations (i.e., its spatial structure), the degree to which adaptive potential is best predicted by variation across the entire genome or the subset of that variation that is identified as putatively adaptive (i.e., its genomic structure), and whether we are managing species as single entities or as collections of diversifying lineages. The distribution of genetic variation and our ultimate goal will have practical implications for on-the-ground management. If adaptive variation is largely polygenic or responsive to change, its spatial structure might be broadly governed by the forces determining genome-wide variation (linked selection, drift, and gene flow), making measurement and prioritization straightforward. If we are managing species as single entities, then population-level prioritization schemes are possible so as to maximize future pooled genetic variation. We outline one such scheme based on the popular Shapley value from cooperative game theory that considers the relative genetic contribution of a population to an unknown future collection of populations.

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 137 554 transcripts with an N50 value of 1437 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.

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.

Cricula trifenestrata Helfer (commonly known as Amphutukoni muga/Cricula silkworm), a wild sericigenous insect produces golden yellow silk similar to Antheraea assamensis (muga silkworm), with significant potential as a natural fiber and biomaterial. Cricula is considered as a pest as it competes for food with muga, which produces the prized golden silk. This study focuses on decoding the mitochondrial genome of C. trifenestrata using next-generation sequencing technology and includes comparative analysis with Bombycoids and other lepidopteran insects. We found that the Cricula mitogenome spans 15 425 bp and exhibits typical gene content and arrangement consistent with other Saturniids and lepidopterans. All protein-coding genes were found to undergo purifying selection, with the highest and lowest conservation observed in the cox1 and atp8 gene, respectively, indicating their potential role in future evolutionary events. We identified two types of mismatches: 23 "G-U" and 6 "U-U" pairs, similar to those found in Actias selene among the Saturniids. Additionally, our study uncovered the presence of two 33 bp repeat units and a "TTAGA" motif in the control region, in contrast to the typical "ATAGA" motif, suggesting functional similarity with evolving sequences. Furthermore, phylogenetic analysis supports the close relationship of Cricula with other species within the Saturniidae family.