Tea plant is an important economic crop, which is used to produce the world's oldest and most widely consumed tea beverages. Here, we present a high-quality reference genome assembly of the tea plant ...(Camellia sinensis var. sinensis) consisting of 15 pseudo-chromosomes. LTR retrotransposons (LTR-RTs) account for 70.38% of the genome, and we present evidence that LTR-RTs play critical roles in genome size expansion and the transcriptional diversification of tea plant genes through preferential insertion in promoter regions and introns. Genes, particularly those coding for terpene biosynthesis proteins, associated with tea aroma and stress resistance were significantly amplified through recent tandem duplications and exist as gene clusters in tea plant genome. Phylogenetic analysis of the sequences of 81 tea plant accessions with diverse origins revealed three well-differentiated tea plant populations, supporting the proposition for the southwest origin of the Chinese cultivated tea plant and its later spread to western Asia through introduction. Domestication and modern breeding left significant signatures on hundreds of genes in the tea plant genome, particularly those associated with tea quality and stress resistance. The genomic sequences of the reported reference and resequenced tea plant accessions provide valuable resources for future functional genomics study and molecular breeding of improved cultivars of tea plants.
A chromosome-level genome assembly of tea plant was presented in this study, which provides novel insights into the evolution of transposable elements and chromosomes of tea plants. Genome analysis showed that genome duplication events drive the amplification of specific genes associated with quality traits. Using resequencing data of 81 diverse accessions, hundreds of candidate domestication genes were identified, some of which were found to be associated with tea quality and stress resistance.
Summary
The tea plant (Camellia sinensis) is a thermophilic cash crop and contains a highly duplicated and repeat‐rich genome. It is still unclear how DNA methylation regulates the evolution of ...duplicated genes and chilling stress in tea plants. We therefore generated a single‐base‐resolution DNA methylation map of tea plants under chilling stress. We found that, compared with other plants, the tea plant genome is highly methylated in all three sequence contexts, including CG, CHG and CHH (where H = A, T, or C), which is further proven to be correlated with its repeat content and genome size. We show that DNA methylation in the gene body negatively regulates the gene expression of tea plants, whereas non‐CG methylation in the flanking region enables a positive regulation of gene expression. We demonstrate that transposable element‐mediated methylation dynamics significantly drives the expression divergence of duplicated genes in tea plants. The DNA methylation and expression divergence of duplicated genes in the tea plant increases with evolutionary age and selective pressure. Moreover, we detect thousands of differentially methylated genes, some of which are functionally associated with chilling stress. We also experimentally reveal that DNA methyltransferase genes of tea plants are significantly downregulated, whereas demethylase genes are upregulated at the initial stage of chilling stress, which is in line with the significant loss of DNA methylation of three well‐known cold‐responsive genes at their promoter and gene body regions. Overall, our findings underscore the importance of DNA methylation regulation and offer new insights into duplicated gene evolution and chilling tolerance in tea plants.
Significance Statement
Our results show solid evidence that DNA methylation not only drives transposable element (TE)‐mediated functional diversification of duplicated genes in the tea plant, but also facilitates the enhancement of chilling tolerance in the tea plant through suppressing the activities of DNA methyltransferase under chilling stress. The overall findings underscore the importance of DNA methylation regulation on gene expression through TE insertions and broaden our understanding of duplicated gene evolution and chilling tolerance in plants.
SUMMARY
Camellia plants include more than 200 species of great diversity and immense economic, ornamental, and cultural values. We sequenced the transcriptomes of 116 Camellia plants from almost all ...sections of the genus Camellia. We constructed a pan‐transcriptome of Camellia plants with 89 394 gene families and then resolved the phylogeny of genus Camellia based on 405 high‐quality low‐copy core genes. Most of the inferred relationships are well supported by multiple nuclear gene trees and morphological traits. We provide strong evidence that Camellia plants shared a recent whole genome duplication event, followed by large expansions of transcription factor families associated with stress resistance and secondary metabolism. Secondary metabolites, particularly those associated with tea quality such as catechins and caffeine, were preferentially heavily accumulated in the Camellia plants from section Thea. We thoroughly examined the expression patterns of hundreds of genes associated with tea quality, and found that some of them exhibited significantly high expression and correlations with secondary metabolite accumulations in Thea species. We also released a web‐accessible database for efficient retrieval of Camellia transcriptomes. The reported transcriptome sequences and obtained novel findings will facilitate the efficient conservation and utilization of Camellia germplasm towards a breeding program for cultivated tea, camellia, and oil‐tea plants.
Significance Statement
High‐quality transcriptomes of 116 Camellia plants from almost all sections of genus Camellia unveils their deep phylogeny and the transcriptional mechanism underlying the dynamic evolution of quality traits related secondary metabolites, which will facilitate the efficient conservation and utilization of Camellia germplasm towards a breeding program for cultivated tea, camellia, and oil‐tea plants.
Tea plant is an important economic crop, which produces the world's oldest and widely consumed tea beverages. We here present a high-quality reference genome of the tea plant (Camellia sinensis var. ...sinensis) consisting of 15 pseudo-chromosomes, 70.38% of which are LTR retrotransposons. We show the evidence that LTR-RTs play critical roles in the genome size expansion and transcriptional diversification of tea plant genes through preferential gene insertions in promoter regions and introns. Genes, particularly those for terpene biosynthesis, associated with tea aroma and stress resistance are significantly amplified forming gene clusters through recent tandem duplications in the tea plant genome. Phylogenetic analyses of the sequences of 81 tea plant accessions of diverse origins revealed three well-differentiated tea plant populations, supporting the proposition for the southwest origin of the cultivated tea plants in China and its later spreading to western Asian through introduction. Domestication and modern breeding left significant signatures on hundreds of genes in the tea plant genome, particularly those associated with tea quality and stress resistance. The genomic sequences of the reported reference and resequenced tea plant accessions provided valuable resources for future functional genomic and breeding research of tea plants and understanding the genome evolution of flowering plants.
A metal–organic framework, UiO-66-NH
2
, was designed, synthesized and characterized in this study. By conducting solvothermal method, Salicylaldehyde (Sal) and 2,4-dihydroxybenzaldehyde (MHBA) were ...grafted onto UiO-66-NH
2
via post-treatment to obtain the functionalized material UiO-66-Sal and UiO-66-MHBA. The three materials above were characterized, and the effects of solid–liquid ratio, pH, ionic strength, and oscillation time on U(VI) adsorption were studied. The relevant experimental results fitted well with pseudo-second-order kinetic equation and thermodynamic adsorption model.
Using VSC-MTDC to provide frequency support for interconnected power systems is an attractive solution. Considering the disadvantages of traditional methods in power shortage or surplus absorption ...into the VSC-MTDC from AC systems requiring active power support (RAPS system) as well as flexible and effective power balance in AC systems providing active power support (PAPS system), this paper proposes a novel frequency support control method for interconnected power systems using VSC-MTDC. The main principle of the proposed frequency support control method is firstly to make the active power shortage or surplus of the RAPS system be fully and naturally absorbed into the DC grid with the AC slack bus mode control proposed for RAPS converters; in addition, the smooth switching control and the power limiting control are further proposed to realize smooth and safe power shortage or surplus absorption. Secondly, according to the proposed flexible PAPS systems matching strategy, one or more appropriate PAPS systems with adequate capacity are selected to effectively and accurately balance the unbalanced power via the corresponding PAPS converters using the active balancing power control. The theoretical analysis and simulation results using PSCAD/EMTDC have verified the validity, flexibility and universality of the proposed frequency support control method.
Spatial and temporal distributions of metal ions in vitro and in vivo are crucial in our understanding of the roles of metal ions in biological systems, and yet there is a very limited number of ...methods to probe metal ions with high space and time resolution, especially in vivo. To overcome this limitation, we report a Zn2+-specific near-infrared (NIR) DNAzyme nanoprobe for real-time metal ion tracking with spatiotemporal control in early embryos and larvae of zebrafish. By conjugating photocaged DNAzymes onto lanthanide-doped upconversion nanoparticles (UCNPs), we have achieved upconversion of a deep tissue penetrating NIR 980 nm light into 365 nm emission. The UV photon then efficiently photodecages a substrate strand containing a nitrobenzyl group at the 2′-OH of adenosine ribonucleotide, allowing enzymatic cleavage by a complementary DNA strand containing a Zn2+-selective DNAzyme. The product containing a visible FAM fluorophore that is initially quenched by BHQ1 and Dabcyl quenchers is released after cleavage, resulting in higher fluorescent signals. The DNAzyme–UCNP probe enables Zn2+ sensing by exciting in the NIR biological imaging window in both living cells and zebrafish embryos and detecting in the visible region. In this study, we introduce a platform that can be used to understand the Zn2+ distribution with spatiotemporal control, thereby giving insights into the dynamical Zn2+ ion distribution in intracellular and in vivo models.
ObjectivesThe measurement of visceral fat (VF) is clinically important for the identification of individuals at high risk of visceral obesity-related health conditions. Bioelectrical impedance ...analysis (BIA) is a widely available and frequently used body composition assessment method, but there have been few validation studies for the measurement of VF. This validation study investigated agreement between BIA and CT for the assessment of VF in adults.DesignCross-sectional study.SettingBetween 2015 and 2016 in China.ParticipantsA total of 414 adults (119 men and 295 women) aged 40–82 years.Primary and secondary outcome measuresCT-visceral fat area (VFA) was derived at the L2-3 and umbilicus level and VFA cut-offs for visceral obesity applied. BIA measurements of visceral fat level were compared with CT VFA findings using scatter plots and receiver operator characteristic (ROC) curves.ResultsScatter plots showed poor agreement between BIA and CT-derived visceral fat measurements in both sexes (R=0.387–0.636). ROC curves gave optimum figures for sensitivity and specificity of 65% and 69% in women and 76% and 70% in men, respectively, for BIA to discriminate between adults with normal levels of VF and those with visceral obesity determined by CT.ConclusionBIA has limited accuracy for the assessment of VF in adults in practice when compared with the criterion method.
Dielectric polymers with high breakdown strength (Eb) and high retention rate of breakdown strength at elevated temperature have important application potential in advanced electrical insulation ...devices. Herein, the aromatic heterocyclic diamine monomer, 5-amino-2-(2-hydroxy-4-aminobenzene)-benzoxazole (HBOA), was synthesized. Theoretical calculation and single crystal date demonstrated fully the formation of intramolecular H-bond of OH⋯NC between benzoxazole and benzene ring in HBOA, which endows the monomer a coplanar geometry. Moreover, the aromatic polyamide films were prepared by polycondensation of HBOA, and the in-plane orientation of films increases with increasing the coplanar HBOA content, which reduces the orientation confusion and cavity of chains packing. When the HBOA content is over 70%, the films exhibit dense-layered stacking structure with high crystallinity. It is found that the dense-layered stacking structure can prevent the films breakdown and failure effectively, which endows the homopolymerization (HBOA-100) film with Eb of 771 kV/mm. Moreover, the Eb of the HBOA-100 film is still as high as 634 kV/mm at 150 °C, and its retention rate of Eb reaches 82% in high temperature environment. In addition, tensile strength of the HBOA-100 film is nearly 343 MPa, glass transition temperature is about 334 °C and the thermal stability up to 487 °C.
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•HBOA and BOA single crystals were obtained, suggesting that the intramolecular hydrogen bond leads to coplanar geometry.•The HBOA monomer and its model compound present layered stacking pattern arising from the coplanar structure.•The dense-layered stacking structure can be constructed in the aromatic polyamide film by the coplanar monomer.•The intrinsic breakdown strength of the homopolymerization film reaches 771 kV/mm and still as high as 634 kV/mm at 150 °C.•This work provides a promising strategy of molecular structure design for high-temperature dielectric polymers.
The demands for massive renewable energy integration, passive network power supply, and global energy interconnection have all gradually increased, posing new challenges for high voltage direct ...current (HVDC) power transmission systems, including more complex topology and increased diversity of bipolar HVDC transmission. This study proposes that these two factors have led to new requirements for HVDC control strategies. Moreover, due to the diverse applications of HVDC transmission technology, each station in the system has different requirements. Furthermore, the topology of the AC-DC converter is being continuously developed, revealing a trend towards hybrid converter stations. Keywords: Direct current transmission system, Topology, Control strategy, AC-DC converter
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