DNA Research最新文献

Gentiana macrophylla is a perennial herb in the Gentianaceae family, whose dried roots are used in traditional Chinese medicine. Here, we assembled a chromosome-level genome of G. macrophylla using a combination of Nanopore, Illumina, and Hi-C scaffolding approaches. The final genome size was ~1.79 Gb (contig N50 = 720.804 kb), and 98.89% of the genome sequences were anchored on 13 pseudochromosomes (scaffold N50 = 122.73 Mb). The genome contained 55,337 protein-coding genes, and 73.47% of the assemblies were repetitive sequences. Genome evolution analysis indicated that G. macrophylla underwent two rounds of whole-genome duplication after the core eudicot γ genome triplication event. We further identified candidate genes related to the biosynthesis of iridoids, and the corresponding gene families mostly expanded in G. macrophylla. In addition, we found that root-specific genes are enriched in pathways involved in defense responses, which may greatly improve the biological adaptability of G. macrophylla. Phylogenomic analyses showed a sister relationship of asterids and rosids, and all Gentianales species formed a monophyletic group. Our study contributes to the understanding of genome evolution and active component biosynthesis in G. macrophylla and provides important genomic resource for the genetic improvement and breeding of G. macrophylla.

A high-quality genome assembly is imperative to explore the evolutionary basis of characteristic attributes that define chemotype and provide essential resources for a molecular breeding strategy for enhanced production of medicinal metabolites. Here, using single-molecule high-fidelity (HiFi) sequencing reads, we report chromosome-scale genome assembly for Chinese licorice (Glycyrrhiza uralensis), a widely used herbal and natural medicine. The entire genome assembly was achieved in eight chromosomes, with contig and scaffold N50 as 36.02 and 60.2 Mb, respectively. With only 17 assembly gaps and half of the chromosomes having no or one assembly gap, the presented genome assembly is among the best plant genomes to date. Our results showed an advantage of using highly accurate long-read HiFi sequencing data for assembling a highly heterozygous genome including its complexed repeat content. Additionally, our analysis revealed that G. uralensis experienced a recent whole-genome duplication at approximately 59.02 million years ago post a gamma (γ) whole-genome triplication event, which contributed to its present chemotype features. The metabolic gene cluster analysis identified 355 gene clusters, which included the entire biosynthesis pathway of glycyrrhizin. The genome assembly and its annotations provide an essential resource for licorice improvement through molecular breeding and the discovery of valuable genes for engineering bioactive components and understanding the evolution of specialized metabolites biosynthesis.

Sesame (Sesamum indicum L.) is an important oilseed crop that produces abundant seed oil and has a pleasant flavor and high nutritional value. To date, several Illumina-based genome assemblies corresponding to different sesame genotypes have been published and widely used in genetic and genomic studies of sesame. However, these assemblies consistently showed low continuity with numerous gaps. Here, we reported a high-quality, reference-level sesame genome assembly by integrating PacBio high-fidelity sequencing and Hi-C technology. Our updated sesame assembly was 309.35 Mb in size with a high chromosome anchoring rate (97.54%) and contig N50 size (13.48 Mb), which were better than previously published genomes. We identified 163.38 Mb repetitive elements and 24,345 high-confidence protein-coding genes in the updated sesame assembly. Comparative genomic analysis showed that sesame shared an ancient whole-genome duplication event with two Lamiales species. A total of 2,782 genes were tandemly duplicated. We also identified several genes that were likely involved in fatty acid and triacylglycerol biosynthesis. Our improved sesame assembly and annotation will facilitate future genetic studies and genomics-assisted breeding of sesame.

Bats (Chiroptera) constitute the second largest order of mammals and have several distinctive features, such as true self-powered flight and strong immunity. The Pendlebury's roundleaf bat, Hipposideros pendleburyi, is endemic to Thailand and listed as a vulnerable species. We employed the 10× Genomics linked-read technology to obtain a genome assembly of H. pendleburyi. The assembly size was 2.17 Gb with a scaffold N50 length of 15,398,518 bases. Our phylogenetic analysis placed H. pendleburyi within the rhinolophoid clade of the suborder Yinpterochiroptera. A synteny analysis showed that H. pendleburyi shared conserved chromosome segments (up to 105 Mb) with Rhinolophus ferrumequinum and Phyllostomus discolor albeit having different chromosome numbers and belonging different families. We found positive selection signals in genes involved in inflammation, spermatogenesis and Wnt signalling. The analyses of transposable elements suggested the contraction of short interspersed nuclear elements (SINEs) and the accumulation of young mariner DNA transposons in the analysed hipposiderids. Distinct mariners were likely horizontally transferred to hipposiderid genomes over the evolution of this family. The lineage-specific profiles of SINEs and mariners might involve in the evolution of hipposiderids and be associated with the phylogenetic separations of these bats from other bat families.

Prunus humilis (2n = 2x = 16) is a dwarf shrub fruit tree native to China and distributed widely in the cold and arid northern region. In this study, we obtained the whole genome sequences of P. humilis by combining Illumina, PacBio and HiC sequencing technologies. This genome was 254.38 Mb long and encodes 28,301 putative proteins. Phylogenetic analysis indicated that P. humilis shares the same ancestor with Prunus mume and Prunus armeniaca at ∼ 29.03 Mya. Gene expansion analysis implied that the expansion of WAX-related and LEA genes might be associated with high drought tolerance of P. humilis and LTR maybe one of the driver factors for the drought adaption by increase the copy number of LEAs. Population diversity analysis among 20 P. humilis accessions found that the genetic diversity of P. humilis populations was limited, only 1.40% base pairs were different with each other, and more wild resources need to be collected and utilized in the breeding and improvement. This study provides new insights to the drought adaption and population diversity of P. humilis that could be used as a potential model plant for horticultural research.

ATP-binding cassette (ABC) proteins are the largest membrane transporter family in plants. In addition to transporting organic substances, these proteins function as ion channels and molecular switches. The development of multiple genes encoding ABC proteins has been associated with their various biological roles. Plants utilize many secondary metabolites to adapt to environmental stresses and to communicate with other organisms, with many ABC proteins thought to be involved in metabolite transport. Lithospermum erythrorhizon is regarded as a model plant for studying secondary metabolism, as cells in culture yielded high concentrations of meroterpenes and phenylpropanoids. Analysis of the genome and transcriptomes of L. erythrorhizon showed expression of genes encoding 118 ABC proteins, similar to other plant species. The number of expressed proteins in the half-size ABCA and full-size ABCB subfamilies was ca. 50% lower in L. erythrorhizon than in Arabidopsis, whereas there was no significant difference in the numbers of other expressed ABC proteins. Because many ABCG proteins are involved in the export of organic substances, members of this subfamily may play important roles in the transport of secondary metabolites that are secreted into apoplasts.