Chromosome-level genome assembly and resequencing of camphor tree (Cinnamomum camphora) provides insight into phylogeny and diversification of terpenoid and triglyceride biosynthesis of Cinnamomum.

Cinnamomum species attract attentions owing to their scents, medicinal properties, and ambiguous relationship in the phylogenetic tree. Here, we report a high-quality genome assembly of Cinnamomum camphora, based on which two whole-genome duplication (WGD) events were detected in the C. camphora genome: one was shared with Magnoliales, and the other was unique to Lauraceae. Phylogenetic analyses illustrated that Lauraceae species formed a compact sister clade to the eudicots. We then performed whole-genome resequencing on 24 Cinnamomum species native to China, and the results showed that the topology of Cinnamomum species was not entirely consistent with morphological classification. The rise and molecular basis of chemodiversity in Cinnamomum were also fascinating issues. In this study, six chemotypes were classified and six main terpenoids were identified as major contributors of chemodiversity in C. camphora by the principal component analysis. Through in vitro assays and subcellular localization analyses, we identified two key terpene synthase (TPS) genes (CcTPS16 and CcTPS54), the products of which were characterized to catalyze the biosynthesis of two uppermost volatiles (i.e. 1,8-cineole and (iso)nerolidol), respectively, and meditate the generation of two chemotypes by transcriptional regulation and compartmentalization. Additionally, the pathway of medium-chain triglyceride (MCT) biosynthesis in Lauraceae was investigated for the first time. Synteny analysis suggested that the divergent synthesis of MCT and long-chain triglyceride (LCT) in Lauraceae kernels was probably controlled by specific medium-chain fatty acyl-ACP thioesterase (FatB), type-B lysophosphatidic acid acyltransferase (type-B LPAAT), and diacylglycerol acyltransferase 2b (DGAT 2b) isoforms during co-evolution with retentions or deletions in the genome.

Strain-induced antipolar phase in hafnia stabilizes robust thin-film ferroelectricity.

Hafnia (HfO2) is a promising candidate for next-generation ferroelectric devices due to its robust ferroelectricity at reduced dimensions and its compatibility with silicon technology. Unfortunately, the origin of robust ferroelectricity and the underlying phase transition mechanism in HfO2 remain elusive. Here, we show that its ferroelectricity arises from two phase transitions, where the primary phase transition to antipolar phase is activated by tensile strain. Above a threshold antipolar mode amplitude, a strong cooperative polar-antipolar coupling enables a second ferroelectric phase transition superimposed on the antipolar phase. Because the antipolar mode is not susceptible to depolarization, this polar-antipolar coupling stabilizes the polarization against depolarization effects. Our results demonstrate that tensile strain and polar-antipolar coupling are the origins of ferroelectricity in HfO2 and provide a previously unknown mechanism against depolarization other than conventional improper ferroelectricity.

Seasonal Variation in the Essential Oil Yield and Composition of Cinnamomum parthenoxylon (Jack) Meisner.

Cinnamomum parthenoxylon (Jack) Meisner is an important natural aromatic plant because its leaves are rich in essential oil. Linalool chemotype C. parthenoxylon was used as the research material in the present study. The leaf essential oil yield, the main chemical components, and their content were measured every month from January to December 2018 to study the seasonal variation in the yield and chemical components of C. parthenoxylon leaf essential oil. The results revealed that the essential oil yield and the main chemical component linalool in the essential oil of C. parthenoxylon leaves showed significant differences among months. The leaf essential oil yield and linalool content decreased to the lowest in March and increased rapidly from April to May. The leaf essential oil yield was the highest in May, and a relatively high yield was maintained from April to August. The linalool content in leaf essential oil was stable in other months except March. The leaf essential oil yield of C. parthenoxylon had a very significant positive correlation with monthly rainfall and monthly average temperature. Intense rainfall and high monthly average temperature were conducive to the synthesis and accumulation of C. parthenoxylon leaf essential oil. This study provided a theoretical basis for cultivating C. parthenoxylon as a raw material for spices and determining the best harvest time.

Identification of RNA helicases in Medicago truncatula and their expression patterns under abiotic stress.

RNA helicase catalyzes the denaturation of DNA or the unwinding of double-stranded RNA. It is vital to RNA splicing, transport, editing, degradation and the initiation of protein translation. However, the function of RNA helicase in Medicago truncatula has rarely been reported. In this study, 170 putative RNA helicase genes were identified in the M. truncatula genome, and classified into three subfamilies based on the presence of either a DEAD-box (52 genes), DEAH-box (38 genes), or DExD/H-box (80 genes) in their coding regions. Additionally, conserved helicase_C domains and other functional domains (e.g., the HA2, DUF, and ZnF domains) were also present in these genes. Chromosomal mapping and synteny analyses showed that there were tandem and segment duplications of RNA helicase genes. Furthermore, transcriptome and real-time PCR analysis showed that the expression of 35 RNA helicase genes was affected by abiotic stress. To be specific, 17, 12 and 19 genes were regulated by salt, drought and cold stress, respectively. It is worth noting that MtDEAD8, MtDEAH3, MtDExD/H18 and MtDExD/H23 responded to all three types of stress. These results provide valuable information for understanding the RNA helicase genes in M. truncatula and their abiotic stress-related functions. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12298-021-01087-y.

Current Status of Research on the Modification of Thermal Properties of Epoxy Resin-Based Syntactic Foam Insulation Materials.

As a lightweight and highly insulating composite material, epoxy resin syntactic foam is increasingly widely used for insulation filling in electrical equipment. To avoid core burning and cracking, which are prone to occur during the casting process, the epoxy resin-based syntactic foam insulation materials with high thermal conductivity and low coefficient of thermal expansion are required for composite insulation equipment. The review is divided into three sections concentrating on the two main aspects of modifying the thermal properties of syntactic foam. The mechanism and models, from the aspects of thermal conductivity and coefficient of thermal expansion, are presented in the first part. The second part aims to better understand the methods for modifying the thermal properties of syntactic foam by adding functional fillers, including the addition of thermally conductive particles, hollow glass microspheres, negative thermal expansion filler and fibers, etc. The third part concludes by describing the existing challenges in this research field and expanding the applicable areas of epoxy resin-based syntactic foam insulation materials, especially cross-arm composite insulation.

Composition-induced type I and direct bandgap transition metal dichalcogenides alloy vertical heterojunctions.

While members of the 2D semiconducting transition metal dichalcogenide (TMD) family MX2 (M = {Mo, W}, X = {S, Se}) are promising for device applications, stacked layer (vertical) heterojunctions exhibit features that make them inappropriate for light-emitting applications. Such vertical heterojunctions exhibit type II, rather than the preferred type I band alignment. Using density functional theory calculations, we identify the pseudo-binary and quaternary alloy composition range for which band alignment is type I. While broad regions of composition space lead to type I band alignment, most light-emitting devices require direct bandgaps. We demonstrate that by taking advantage of alloying and/or twisting between layers, a wide range of type I, direct bandgap stacked layer (vertical) heterojunctions are achievable. These results and the underlying method developed here provide new opportunities for TMD vertical heterojunction device optimization and opens the door to new classes of TMD vertical heterojunction device applications.

The MoSeS dynamic omnigami paradigm for smart shape and composition programmable 2D materials.

The properties of 2D materials can be broadly tuned through alloying and phase and strain engineering. Shape programmable materials offer tremendous functionality, but sub-micron objects are typically unachievable with conventional thin films. Here we propose a new approach, combining phase/strain engineering with shape programming, to form 3D objects by patterned alloying of 2D transition metal dichalcogenide (TMD) monolayers. Conjugately, monolayers can be compositionally patterned using non-flat substrates. For concreteness, we focus on the TMD alloy MoSe[Formula: see text]S[Formula: see text]; i.e., MoSeS. These 2D materials down-scale shape/composition programming to nanoscale objects/patterns, provide control of both bending and stretching deformations, are reversibly actuatable with electric fields, and possess the extraordinary and diverse properties of TMDs. Utilizing a first principles-informed continuum model, we demonstrate how a variety of shapes/composition patterns can be programmed and reversibly modulated across length scales. The vast space of possible designs and scales enables novel material properties and thus new applications spanning flexible electronics/optics, catalysis, responsive coatings, and soft robotics.

Synthesis and Physical Properties of Phase-Engineered Transition Metal Dichalcogenide Monolayer Heterostructures.

Heterostructures of transition metal dichalcogenides (TMDs) offer the attractive prospect of combining distinct physical properties derived from different TMD structures. Here, we report direct chemical vapor deposition of in-plane monolayer heterostructures based on 1H-MoS2 and 1T'-MoTe2. The large lattice mismatch between these materials led to intriguing phenomena at their interface. Atomic force microscopy indicated buckling in the 1H region. Tip-enhanced Raman spectroscopy showed mode structure consistent with Te substitution in the 1H region during 1T'-MoTe2 growth. This was confirmed by atomic resolution transmission electron microscopy, which also revealed an atomically stitched, dislocation-free 1H/1T' interface. Theoretical modeling revealed that both the buckling and absence of interfacial misfit dislocations were explained by lateral gradients in Te substitution levels within the 1H region and elastic coupling between 1H and 1T' domains. Phase field simulations predicted 1T' morphologies with spike-shaped islands at specific orientations consistent with experiments. Electrical measurements across the heterostructure confirmed its electrical continuity. This work demonstrates the feasibility of dislocation-free stitching of two different atomic configurations and a pathway toward direct synthesis of monolayer TMD heterostructures of different phases.

Dynamic Phase Engineering of Bendable Transition Metal Dichalcogenide Monolayers.

Current interest in two-dimensional (2D) materials is driven in part by the ability to dramatically alter their optoelectronic properties through strain and phase engineering. A combination of these approaches can be applied in quasi-2D transition metal dichalcogenide (TMD) monolayers to induce displacive structural transformations between semiconducting (H) and metallic/semimetallic (T') phases. We classify such transformations in Group VI TMDs, and formulate a multiscale, first-principles-informed modeling framework to describe evolution of microstructural domain morphologies in elastically bendable 2D monolayers. We demonstrate that morphology and mechanical response can be controlled via application of strain either uniformly or through local probes to generate functionally patterned conductive T' domains. Such systems form dynamically programmable electromechanical 2D materials, capable of rapid local switching between domains with qualitatively different transport properties. This enables dynamic "drawing" of localized conducting regions in an otherwise semiconducting TMD monolayer, opening several interesting device-relevant functionalities such as the ability to dynamically "rewire" a device in real time.

Inhibition of lipopolysaccharide-induced iNOS and COX-2 expression by indole alkaloid, 3-(hydroxymethyl)-6,7-dihydroindolo[2,3-a]quinolizin-(12H)-one, via NF-κB inactivation in RAW 264.7 macrophages.

3-(Hydroxymethyl)-6,7-dihydroindolo[2,3-a]quinolizin-(12H)-one is a bioactive indole alkaloid isolated from Nauclea officinalis, a plant species which is used as a traditional Chinese medicine. We investigated the anti-inflammatory properties of 3-(hydroxymethyl)-6,7-dihydroindolo[2,3-a]quinolizin-(12H)-one in RAW 264.7 murine macrophages. The results indicated that it inhibited the overproduction of NO and the release of TNF-α. Furthermore, this compound inhibited the expression of iNOS and COX-2 proteins, the enzymatic activity of iNOS, and the translocation of NF-κB to the nucleus induced by LPS. Therefore, we suggested that the effect of 3-(hydroxymethyl)-6,7-dihydroindolo[2,3-a]quinolizin-(12H)-one-mediated inhibition of the expression of LPS-induced iNOS and COX-2 genes is due to the suppression of NF-κB activation in the transcriptional level.