DNA Research最新文献

To adapt to high-altitude habitats, many alpine plants develop self-compatible breeding systems from outcrossing. The genetic bases for this shift and the resulting demographic consequences remain largely unexplored. Here, we present a high-quality, chromosome-level genome assembly of the monotypic and endangered alpine perennial Przewalskia tangutica (Solanaceae) occurring on the Qinghai-Tibet Plateau (QTP). Our assembled genome is approximately 3 Gb, with a contig N50 size of 17 Mb, and we identified one lineage-specific whole-genome duplication. We found that the gametophytic self-incompatibility (GSI) syntenic locus to the other obligate outcrossing Solanaceae species was broken by the inserted the long terminal repeats, and changes in the flower-specific expression of the homologous genes, and the linked GSI genes in this species. Such changes may have led to its self-compatibility. We identified three deeply diverged lineages in the central distribution of this species, and the gene flow between them was weak but continuous. All three lineages diverged and decreased their population sizes since the largest glaciations occurred in the QTP approximately 720-500 thousand years ago. In addition, we identified one obvious hybrid population between two lineages, suggesting that genetic exchanges between and within lineages still occur. Our results provide insights into evolutionary adaptation through facultative self-pollination and demographic consequences of this alpine rare species in arid habitats.

Tetraena mongolica is an endangered xerophytic shrub with high ecological value for the restoration of desert vegetation because of its high tolerance to drought and heat stress. Here, we generated a high-quality chromosome-level reference genome of T. mongolica by combining PacBio HiFi data and Hi-C sequencing technologies, which was approximately 1.12 Gb (contig N50 of 25.5 Mb) in size and contained 61,888 protein-coding genes; repetitive sequences comprised 44.8% of the genome. This genome of T. mongolica is the first published genome sequence of a member of the order Zygophyllales. Genome analysis showed that T. mongolica has undergone a recent whole genome duplication event, and a recent burst of long terminal repeat insertions afterward, which may be responsible for its genome size expansion and drought adaptation. We also conducted searches for gene homologues and identified terpene synthase (TPS) gene families and candidate genes involved in triacylglycerol biosynthesis. The T. mongolica genome sequence could aid future studies aimed at functional gene identification, germplasm resource management, molecular breeding efforts, as well as evolutionary studies of Fabids and angiosperm taxa.

Kobresia species are common in meadows on the Qinghai-Tibet Plateau. They are important food resources for local livestock, and serve a critical foundation for ecosystem integration. Genetic resources of Kobresia species are scarce. Here, we generated a chromosome-level genome assembly for K. myosuroides (Cyperaceae), using PacBio long-reads, Illumina short-reads, and Hi-C technology. The final assembly had a total size of 399.9 Mb with a contig N50 value of 11.9 Mb. The Hi-C result supported a 29 pseudomolecules model which was in consistent with cytological results. A total of 185.5 Mb (44.89% of the genome) transposable elements were detected, and 26,748 protein-coding genes were predicted. Comparative analysis revealed that Kobresia plants have experienced recent diversification events during the late Miocene to Pliocene. Karyotypes analysis indicated that the fission and fusion of chromosomes have been a major driver of speciation, which complied with the lack of whole-genome duplication (WGD) in K. myosuroides genome. Generally, this high-quality reference genome provides insights into the evolution of alpine sedges, and may be helpful to endemic forage improvement and alpine ecosystem preservation.

Mycorrhizae are one of the most fundamental symbioses between plants and fungi, with ectomycorrhizae being the most widespread in boreal forest ecosystems. Ectomycorrhizal fungi are hypothesized to have evolved convergently from saprotrophic ancestors in several fungal clades, especially members of the subdivision Agaricomycotina. Studies on fungal genomes have identified several typical characteristics of mycorrhizal fungi, such as genome size expansion and decreases in plant cell-wall degrading enzymes (PCWDEs). However, genomic changes concerning the evolutionary transition to the ectomycorrhizal lifestyle are largely unknown. In this study, we sequenced the genome of Lyophyllum shimeji, an ectomycorrhizal fungus that is phylogenetically related to saprotrophic species and retains some saprotroph-like traits. We found that the genome of Ly. shimeji strain AT787 lacks both incremental increases in genome size and reduced numbers of PCWDEs. Our findings suggest that the previously reported common genomic traits of mycorrhizal fungi are not essential for the ectomycorrhizal lifestyle, but are a result of abolishing saprotrophic activity. Since Ly. shimeji is commercially consumed as an edible mushroom, the newly available genomic information may also impact research designed to enhance the cultivation of this mushroom.

The ladybird beetle Henosepilachna vigintioctomaculata is an economically significant oligophagous pest that induces damage to many Solanaceae crops. An increasing number of studies have examined the population and phenotype diversity of ladybird beetles. However, few comparative genome analyses of ladybird beetle species have been conducted. Here, we obtained a high-quality chromosome-level genome assembly of H. vigintioctomaculata using various sequencing technologies, and the chromosome-level genome assembly was ~581.63 Mb, with 11 chromosomes successfully assembled. The phylogenetic analysis showed that H. vigintioctomaculata is a more ancient lineage than the other three sequenced ladybird beetles, Harmonia axyridis, Propylea japonica, and Coccinella septempunctata. We also compared positively selected genes (PSGs), transposable elements (TEs) ratios and insertion times, and key gene families associated with environmental adaptation among these ladybird beetles. The pattern of TEs evolution of H. vigintioctomaculata differs from the other three ladybird beetles. The PSGs were associated with ladybird beetles development. However, the key gene families associated with environmental adaptation in ladybird beetles varied. Overall, the high-quality draft genome sequence of H. vigintioctomaculata provides a useful resource for studies of beetle biology, especially for the invasive biology of ladybird beetles.

Perilla frutescens (Lamiaceae) is an important herbal plant with hundreds of bioactive chemicals, among which perillaldehyde and rosmarinic acid are the two major bioactive compounds in the plant. The leaves of red perilla are used as traditional Kampo medicine or food ingredients. However, the medicinal and nutritional uses of this plant could be improved by enhancing the production of valuable metabolites through the manipulation of key enzymes or regulatory genes using genome editing technology. Here, we generated a high-quality genome assembly of red perilla domesticated in Japan. A near-complete chromosome-level assembly of P. frutescens was generated contigs with N50 of 41.5 Mb from PacBio HiFi reads. 99.2% of the assembly was anchored into 20 pseudochromosomes, among which seven pseudochromosomes consisted of one contig, while the rest consisted of less than six contigs. Gene annotation and prediction of the sequences successfully predicted 86,258 gene models, including 76,825 protein-coding genes. Further analysis showed that potential targets of genome editing for the engineering of anthocyanin pathways in P. frutescens are located on the late-stage pathways. Overall, our genome assembly could serve as a valuable reference for selecting target genes for genome editing of P. frutescens.

The New World Screwworm, Cochliomyia hominivorax (Calliphoridae), is the most important myiasis-causing species in America. Screwworm myiasis is a zoonosis that can cause severe lesions in livestock, domesticated and wild animals, and occasionally in people. Beyond the sanitary problems associated with this species, these infestations negatively impact economic sectors, such as the cattle industry. Here, we present a chromosome-scale assembly of C. hominivorax's genome, organized in 6 chromosome-length and 515 unplaced scaffolds spanning 534 Mb. There was a clear correspondence between the D. melanogaster linkage groups A-E and the chromosomal-scale scaffolds. Chromosome quotient (CQ) analysis identified a single scaffold from the X chromosome that contains most of the orthologs of genes that are on the D. melanogaster fourth chromosome (linkage group F or dot chromosome). CQ analysis also identified potential X and Y unplaced scaffolds and genes. Y-linkage for selected regions was confirmed by PCR with male and female DNA. Some of the long chromosome-scale scaffolds include Y-linked sequences, suggesting misassembly of these regions. These resources will provide a basis for future studies aiming at understanding the biology and evolution of this devastating obligate parasite.

The genome contains large functional units ranging in size from hundreds of kilobases to megabases, such as gene clusters and topologically associating domains. To analyse these large functional units, the technique of deleting the entire functional unit is effective. However, deletion of such large regions is less efficient than conventional genome editing, especially in cultured cells, and a method that can ensure success is anticipated. Here, we compared methods to delete the 2.5-Mb Krüppel-associated box zinc finger protein (KRAB-ZFP) gene cluster in mouse embryonic stem cells using CRISPR-Cas9. Three methods were used: first, deletion by non-homologous end joining (NHEJ); second, homology-directed repair (HDR) using a single-stranded oligodeoxynucleotide (ssODN); and third, HDR employing targeting vectors with a selectable marker and 1-kb homology arms. NHEJ-mediated deletion was achieved in 9% of the transfected cells. Inversion was also detected at similar efficiency. The deletion frequency of NHEJ and HDR was found to be comparable when the ssODN was transfected. Deletion frequency was highest when targeting vectors were introduced, with deletions occurring in 31-63% of the drug-resistant clones. Biallelic deletion was observed when targeting vectors were used. This study will serve as a benchmark for the introduction of large deletions into the genome.

Amaranthus tricolor is a vegetable and ornamental amaranth, with high lysine, dietary fibre and squalene content. The red cultivar of A. tricolor possesses a high concentration of betalains, which has been used as natural food colorants. Here, we constructed the genome of A. tricolor, the first reference genome for the subgenus Albersia, combining PacBio HiFi, Nanopore ultra-long and Hi-C data. The contig N50 size was 906 kb, and 99.58% of contig sequence was anchored to the 17 chromosomes, totalling 520 Mb. We annotated 27,813 protein-coding genes with an average 1.3 kb coding sequence and 5.3 exons. We inferred that A. tricolor underwent a whole-genome duplication (WGD) and that the WGD shared by amaranths occurred in the last common ancestor of subfamily Amaranthoideae. Moreover, we comprehensively identified candidate genes in betalain biosynthesis pathway. Among them, DODAα1 and CYP76ADα1, located in one topologically associated domain (TAD) of an active (A) compartment on chromosome 16, were more highly expressed in red leaves than in green leaves, and DODAα1 might be the rate-limiting enzyme gene in betalains biosynthesis. This study presents new genome resources and enriches our understanding of amaranth evolution, betalains production, facilitating molecular breeding improvements and the understanding of C4 plants evolution.