DNA Research最新文献

Hibiscus trionum, commonly known as the 'Flower of an Hour', is an easily cultivated plant in the Malvaceae family that is widespread in tropical and temperate regions, including drylands. The purple base part of its petal exhibits structural colour due to the fine ridges on the epidermal cell surface, and the molecular mechanism of ridge formation has been actively investigated. We performed genome sequencing of H. trionum using a long-read sequencing technology with transcriptome and pathway analyses to identify candidate genes for fine structure formation. The ortholog of AtSHINE1, which is involved in the biosynthesis of cuticular wax in Arabidopsis thaliana, was significantly overexpressed in the iridescent tissue. In addition, orthologs of AtCUS2 and AtCYP77A, which contribute to cutin synthesis, were also overexpressed. Our results provide important insights into the formation of fine ridges on epidermal cells in plants using H. trionum as a model.

Plantago is a major genus belonging to the Plantaginaceae family and is used in herbal medicine, functional food, and pastures. Several Plantago species are also characterized by their global distribution, but the mechanism underpinning this is not known. Here, we present a high-quality, chromosome-level genome assembly of Plantago major L., a species of Plantago, by incorporating Oxford Nanopore sequencing and Hi-C technologies. The genome assembly size was approximately 671.27 Mb with a contig N50 length of 31.30 Mb. 31,654 protein-coding genes were identified from the genome. Evolutionary analysis showed that P. major diverged from other Lamiales species at ~62.18 Mya and experienced two rounds of WGD events. Notably, many gene families related to plant acclimation and adaptation expanded. We also found that many polyphenol biosynthesis genes showed high expression patterns in roots. Some amino acid biosynthesis genes, such as those involved in histidine synthesis, were highly induced under metal (Ni) stress that led to the accumulation of corresponding metabolites. These results suggest persuasive arguments for the global distribution of P. major through multiscale analysis. Decoding the P. major genome provides a valuable genomic resource for research on dissecting biological function, molecular evolution, taxonomy, and breeding.

The restriction enzymes examined so far are phosphodiesterases, which cleave DNA strands by hydrolysing phosphodiester bonds. Based on the mobility of restriction-modification systems, recent studies have identified a family of restriction enzymes that excise a base in their recognition sequence to generate an abasic (AP) site unless the base is properly methylated. These restriction glycosylases also show intrinsic but uncoupled AP lyase activity at the AP site, generating an atypical strand break. Action of an AP endonuclease at the AP site may generate another atypical break, rejoining/repairing of which is difficult. This PabI family of restriction enzymes contain a novel fold (HALFPIPE) and show unusual properties, such as non-requirement of divalent cations for cleavage. These enzymes are present in Helicobacteraceae/Campylobacteraceae and in few hyperthermophilic archaeal species. In Helicobacter genomes, their recognition sites are strongly avoided, and the encoding genes are often inactivated by mutations or replacement, indicating that their expression is toxic for the cells. The discovery of restriction glycosylases generalizes the concept of restriction-modification systems to epigenetic immune systems, which may use any mode of damage to DNA that are considered 'non-self' based on epigenetic modifications. This concept will add to our understanding of immunity and epigenetics.

Vestimentiferan tubeworms are representative members of deep-sea chemosynthetic ecosystems. In this study, we developed a draft genome and gene models and performed genomic and transcriptomic analyses of Lamellibrachia satsuma, the only vestimentiferan reported from the euphotic zone. The quality of the genome assembly and gene models is comparable to or higher than those of previously reported vestimentiferan tubeworms. Tissue-specific transcriptome sequencing revealed that Toll-like receptor genes and lineage-specific expanded bacteriolytic enzyme genes are highly expressed in the obturacular and vestimental regions, respectively, suggesting the importance of these tissues in defense against pathogens. On the other hand, globin subunit genes are expressed almost exclusively in the trunk region, supporting the hypothesis that the trophosome is the site of haemoglobin biosynthesis. Vestimentiferan-specific expanded gene families included chitinases, ion channels, and C-type lectins, suggesting the importance of these functions for vestimentiferans. C-type lectins in the trunk region, in particular, may be involved in recognition of pathogens, or in interactions between tubeworms and symbiotic bacteria. Our genomic and transcriptomic analyses enhance understanding of molecular mechanisms underlying the unique lifestyle of vestimentiferan tubeworms, particularly their obligate mutualism with chemosynthetic bacteria.

The prediction of gene structure within the genome sequence is the starting point of genome analysis, and its accuracy has a significant impact on the quality of subsequent analyses. Gene structure prediction is roughly divided into RNA-Seq-based methods, ab initio-based methods, homology-based methods, and the integration of individual prediction methods. Integrated methods are mainstream in recent genome projects because they improve prediction accuracy by combining or taking the best individual prediction findings; however, adequate prediction accuracy for eukaryotic species has not yet been achieved. Therefore, we developed an integrated tool, GINGER, that solves various issues related to gene structure prediction in higher eukaryotes. By handling artefacts in alignments of RNA and protein sequences, reconstructing gene structures via dynamic programming with appropriately weighted and scored exon/intron/intergenic regions, and applying different prediction processes and filtering criteria to multi-exon and single-exon genes, we achieved a significant improvement in accuracy compared to the existing integration methods. The feature of GINGER is its high prediction accuracy at the gene and exon levels, which is pronounced for species with more complex gene architectures. GINGER is implemented using Nextflow, which allows for the efficient and effective use of computing resources.

Prunus mongolica is an ecologically and economically important xerophytic tree native to Northwest China. Here, we report a high-quality, chromosome-level P. mongolica genome assembly integrating PacBio high-fidelity sequencing and Hi-C technology. The assembled genome was 233.17 Mb in size, with 98.89% assigned to eight pseudochromosomes. The genome had contig and scaffold N50s of 24.33 Mb and 26.54 Mb, respectively, a BUSCO completeness score of 98.76%, and CEGMA indicated that 98.47% of the assembled genome was reliably annotated. The genome contained a total of 88.54 Mb (37.97%) of repetitive sequences and 23,798 protein-coding genes. We found that P. mongolica experienced two whole-genome duplications, with the most recent event occurring ~3.57 million years ago. Phylogenetic and chromosome syntenic analyses revealed that P. mongolica was closely related to P. persica and P. dulcis. Furthermore, we identified a number of candidate genes involved in drought tolerance and fatty acid biosynthesis. These candidate genes are likely to prove useful in studies of drought tolerance and fatty acid biosynthesis in P. mongolica, and will provide important genetic resources for molecular breeding and improvement experiments in Prunus species. This high-quality reference genome will also accelerate the study of the adaptation of xerophytic plants to drought.

Grafting is widely used as a method to increase stress tolerance in good fruiting lines of Solanaceae plants. However, little is known about how grafting, affects epigenetic modifications and leads to stress tolerance, especially within the same line. Here, we studied the effects of self-grafting in tomato plants on histone and DNA modifications and changes in gene expression related to drought stress. We found that at the three-leaf stage, 1 week after self-grafting, histone H3 K4 trimethylation and K27 trimethylation changes were observed in more than 500 genes each, and DNA methylation changes in more than 5,000 gene regions at the shoot apex compared to the non-grafted control. In addition, two weeks after the epigenomic changes, global expression changes continued to be observed at the shoot apex in several genes related to the metabolic process of nitrogen compounds, responses to stimulus, chromosome organization, cell cycle-related genes, and regulation of hormone levels. Finally, these grafted seedlings acquired remarkable drought tolerance, suggesting that epigenomic modifications during the wound-healing process mitigate stress tolerance in tomato plants.

To quantify the biases introduced during human gut microbiome studies, analyzing an artificial mock community as the reference microbiome is indispensable. However, there are still limited resources for a mock community which well represents the human gut microbiome. Here, we constructed a novel mock community comprising the type strains of 18 major bacterial species in the human gut and assessed the influence of experimental and bioinformatics procedures on the 16S rRNA gene and shotgun metagenomic sequencing. We found that DNA extraction methods greatly affected the DNA yields and taxonomic composition of sequenced reads, and that some of the commonly used primers for 16S rRNA genes were prone to underestimate the abundance of some gut commensal taxa such as Erysipelotrichia, Verrucomicrobiota and Methanobacteriota. Binning of the assembled contigs of shotgun metagenomic sequences by MetaBAT2 produced phylogenetically consistent, less-contaminated bins with varied completeness. The ensemble approach of multiple binning tools by MetaWRAP can improve completeness but sometimes increases the contamination rate. Our benchmark study provides an important foundation for the interpretation of human gut microbiome data by providing means for standardization among gut microbiome data obtained with different methodologies and will facilitate further development of analytical methods.

The Mediterranean lizard Podarcis lilfordi is an emblematic species of the Balearic Islands. The extensive phenotypic diversity among extant isolated populations makes the species a great insular model system for eco-evolutionary studies, as well as a challenging target for conservation management plans. Here we report the first high-quality chromosome-level assembly and annotation of the P. lilfordi genome, along with its mitogenome, based on a mixed sequencing strategy (10X Genomics linked reads, Oxford Nanopore Technologies long reads and Hi-C scaffolding) coupled with extensive transcriptomic data (Illumina and PacBio). The genome assembly (1.5 Gb) is highly contiguous (N50 = 90 Mb) and complete, with 99% of the sequence assigned to candidate chromosomal sequences and >97% gene completeness. We annotated a total of 25,663 protein-coding genes translating into 38,615 proteins. Comparison to the genome of the related species Podarcis muralis revealed substantial similarity in genome size, annotation metrics, repeat content, and a strong collinearity, despite their evolutionary distance (~18-20 MYA). This genome expands the repertoire of available reptilian genomes and will facilitate the exploration of the molecular and evolutionary processes underlying the extraordinary phenotypic diversity of this insular species, while providing a critical resource for conservation genomics.

The genetic bases of halophytes for salinity tolerance are crucial for genetically breeding salt-tolerant crops. All natural Nitrariaceae species that exclusively occur in arid environments are highly tolerant to salt stress, but the underlying genomic bases to this adaptation remain unknown. Here we present a high-quality, chromosome-level genome sequence of Nitraria sibirica, with an assembled size of 456.66 Mb and 23,365 annotated genes. Phylogenomic analyses confirmed N. sibirica as the sister to all other sampled representatives from other families in Sapindales, and no lineage-specific whole-genome duplication was found except the gamma triplication event. Still, we found that the genes involved in K + retention, energy supply, and Fe absorption expanded greatly in N. sibirica. Deep transcriptome analyses showed that leaf photosynthesis and cuticular wax formation in roots were enhanced under salt treatments. Furthermore, many transcription factors involved in salt tolerance changed their expressions significantly and displayed tissue- and concentration-dependent signaling in response to salt stress. Additionally, we found vacuolar Na + compartmentalization is an ongoing process under salt treatment, while Na + exclusion tends to function at high salt concentrations. These genomic and transcriptomic changes conferred salt tolerance in N. sibirica and pave the way for future breeding of salt-tolerant crops.