Identification of the Key Pathways and Genes Involved in the Wax Biosynthesis of the Chinese White Wax Scale Insect (Ericerus pela Chavannes) by Integrated Weighted Gene Coexpression Network Analysis.

The white wax secreted by the male insects of the Chinese white wax scale (CWWS) is a natural high-molecular-weight compound with important economic value. However, its regulatory mechanism of wax biosynthesis is still unclear. In this study, a weighted gene coexpression network analysis (WGCNA) was used to analyze transcriptome data of first- and second-instar females, early and late female adults, and first- and second-instar males. A total of 19 partitioned modules with different topological overlaps were obtained, and three modules were identified as highly significant for wax secretion (p < 0.05). A total of 30 hub genes were obtained through screening, among which elongation of very-long-chain fatty acids protein (ELOVL) and fatty acyl-CoA reductase (FAR) are important catalytic enzymes of fatty acid metabolism. Furthermore, their metabolic catalytic products are involved in the synthesis of wax biosynthesis. The results demonstrate that WGCNA can be used for insect transcriptome analysis and effectively screen out the key genes related to wax biosynthesis.

Characterization of Potential Molecular Markers in Lac Insect Kerria lacca (Kerr) Responsible for Lac Production.

Kerria lacca (Kerr) is an important lac insect extensively used in industrial products in the form of resin, wax and dye. The scarce knowledge on molecular markers for K. lacca is a barrier in elucidating genetic information. Our study identified a total of 16,921 single-nucleotide polymorphisms (SNPs), and 6231 insertions and deletions (InDels)-of which, intergenic variation accounted for 41.22% and 56.30%, and exonic variation accounted for 39.10% and 17.46%, of SNPs and InDels, respectively. Observation of SNPs suggested that nucleotide substitution frequency and transition to transversion (Ts/Tv) ratio were highest at the late adult stage, 3.97, compared to at the other stages, with a genome-wide Ts/Tv ratio of 2.95. The maximum number of SNPs, 2853 (16.86%), was identified in chromosome 8, while the lowest, 1126 (6.65%), was identified in chromosome 7. The maximum and minimum numbers of InDels were located on chromosome 1 and 7, with 834 (13.38%) and 519 (8.33%), respectively. Annotation showed that highest numbers of exonic and intergenic SNPs were present at the late adult stage, whereas the maximum number of InDels was found at the larval stage. On the basis of gene function, 47 gene variations were screened and 23 candidate genes were identified in associations with lac production. Concluding work will enhance knowledge on molecular markers to facilitate an increase in lac production in K. lacca as well as other lac insects.

Genome assembly and methylome analysis of the white wax scale insect provides insight into sexual differentiation of metamorphosis in hexapods.

Scale insects are hemimetabolous, showing "incomplete" metamorphosis and no true pupal stage. Ericerus pela, commonly known as the white wax scale insect (hereafter, WWS), is a wax-producing insect found in Asia and Europe. WWS displays dramatic sexual dimorphism, with notably different metamorphic fates in males and females. Males develop into winged adults, while females are neotenic and maintain a nymph-like appearance, which are flightless and remain stationary. Here, we report the de novo assembly of the WWS genome with a size of 638.30 Mbp (69.68 Mbp for scaffold N50) by PacBio sequencing and Hi-C. These data allowed us to perform a robust phylogenetic analysis comprising 24,923 gene orthogroups from 16 representative insect genomes. This analysis indicated that holometabola evolved from insects with incomplete metamorphosis in the Late Carboniferous, about 50 million years earlier than previously thought. To study the distinct developmental fates of males and females, we analysed the methylome landscape in either sex. Surprisingly, WWS displayed high methylation levels (4.42% for males) when compared to other insects. We observed differential methylation patterns in males and females for genes involved in steroid and sesquiterpenoid production as well as genes acting in fatty acid metabolism pathways. We measured titre profiles for ecdysone, the principal insect steroid hormone, and juvenile hormone (a sesquiterpenoid) in both males and females, which suggested that these hormones are the primary drivers of sexually dimorphic development. Our results provide a comprehensive genomic and epigenomic resource of scale insects that provide new insights into the evolution of metamorphosis and sexual dimorphism in insects.

Preparation of Ni3Fe2@NC/CC Integrated Electrode and Its Application in Zinc-Air Battery.

Reasonable design and development of a low-cost and high-efficiency bifunctional electrocatalyst for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is essential for promoting the development of Zinc-air battery technology. Herein, we obtained an integrated catalytic electrode, NiFe nanoparticles supported on nitrogen-doped carbon (NC) directly grown on the carbon cloth (designated as Ni3Fe2@NC/CC), by pyrolysis of bimetallic NiFe metal-organic framework (MOF) precursor. There is a synergistic effect between nickel and iron component, which enhances the bifunctional catalytic activity. In addition, the underlying carbon cloth is conducive to the efficient electron transfer and also benefits the uniform loading of catalytically active materials. Thus, the integrated electrode shows good OER/ORR dual-functional catalytic performance, and the OER overpotential is much lower than that of the traditional drop-coating electrode and precious metal catalyst (IrO2). Moreover, the Ni3Fe2@NC/CC integrated electrode used in zinc-air batteries shows good flexibility and cycle stability. Our findings provide a new avenue for the development of efficient and stable bifunctional oxygen electrocatalysts.

Controlled Synthesis of Ni-Doped MoS2 Hybrid Electrode for Synergistically Enhanced Water-Splitting Process.

The development of high-efficiency, low-cost, and earth-abundant electrocatalysts for overall water splitting remains a challenge. In this work, Ni-modified MoS2 hybrid catalysts are grown on carbon cloth (Ni-Mo-S@CC) through a one-step hydrothermal treatment. The optimized Ni-Mo-S@CC catalyst shows excellent hydrogen evolution reaction (HER) activity with a low overpotential of 168 mV at a current density of 10 mA cm-2 in 1.0 m KOH, which is lower than those of Ni-Mo-S@CC (1:1), Ni-Mo-S@CC (3:1), and pure MoS2 . Significantly, the Ni-Mo-S@CC hybrid catalyst also displays outstanding oxygen evolution reaction (OER) activity with a low overpotential of 320 mV at a current density of 10 mA cm-2 , and remarkable long-term stability for 30 h at a constant current density of 10 mA cm-2 . Experimental results and theoretical analysis based on density functional theory demonstrate that the excellent electrocatalytic performance can be attributed mainly to the remarkable conductivity, abundant active sites, and synergistic effect of the Ni-doped MoS2 . This work sheds light on a unique strategy for the design of high-performance and stable electrocatalysts for water-splitting electrolyzers.

Potential Pathways and Genes Involved in Lac Synthesis and Secretion in Kerria chinensis (Hemiptera: Kerriidae) Based on Transcriptomic Analyses.

Lac is a type of natural resin secreted by lac insects and is widely used in the military and other industries because of its excellent adhesion and insulation properties. The main ingredients of lac are lactones and lactides, which are formed from hydroxy fatty acids and sesquiterpene esters. In this study, we measured lac secretion rates by the insect Kerria chinensis at different developmental stages and identified lac secretion-minimum and lac secretion-active stages of the insect. We then analyzed transcriptomes of lac secretion-minimum and lac secretion-active stages of the insect. Based on expression profiles of genes in different stages of the insect, we identified pathways and genes that are potentially involved in lac synthesis and secretion in K. chinensis. Our study lays a foundation for future studies to reveal the molecular mechanisms and pathways of lac synthesis and secretion in this beneficial insect.

Porous Zinc Anode Design for Zn-air Chemistry.

Zinc-air battery has drawn increasing attention from the whole world owing to its large energy capacity, stable working voltage, environmentally friendship, and low price. A special porous Zn with three-dimensional (3D) network frame structure, whose multistage average pore sizes can be tuned from 300 to 8 um, is synthesized in this work. It is found that there is a competition between Zn2+ and NH 4 + for their reduction on the supports. And the decrease of Zn2+ concentration and increase of NH 4 + concentration can facilitate the decrease of pore size. Potential-dynamic polarization was tested with 3-electrodes cell, aiming to characterize the electrochemical activity and corrosion properties of porous Zn and commercial Zn foil electrodes. After optimization, the porous Zn prepared with the parameters of 3 M NaBr, 1 M C2H3O2NH4, and 0.01 M C4H6O4Zn shows the most negative corrosion potential of -1.45 V among all the samples, indicating the remarkable anti-corrosion property. Its discharge specific capacity is up to 812 mAh g-1. And discharge-charge test of the porous Zn shows an initial discharge platform of 1.33 V and an initial charge platform of 1.96 V, performing a small overpotential. What's more, the porous Zn exhibits a much longer cycle life than commercial Zn foil. Our work will not only shed light on the design and synthesis of other porous metal materials, but also further promote the development of Zn-based battery electrochemistry.

Atomically Dispersed Binary Co-Ni Sites in Nitrogen-Doped Hollow Carbon Nanocubes for Reversible Oxygen Reduction and Evolution.

With the inspiration of developing bifunctional electrode materials for reversible oxygen electrocatalysis, one strategy of heteroatom doping is proposed to fabricate dual metal single-atom catalysts. However, the identification and mechanism functions of polynary single-atom structures remain elusive. Atomically dispersed binary Co-Ni sites embedded in N-doped hollow carbon nanocubes (denoted as CoNi-SAs/NC) are synthesized via proposed pyrolysis of dopamine-coated metal-organic frameworks. The atomically isolated bimetallic configuration in CoNi-SAs/NC is identified by combining microscopic and spectroscopic techniques. When employing as oxygen electrocatalysts in alkaline medium, the resultant CoNi-SAs/NC hybrid manifests outstanding catalytic performance for bifunctional oxygen reduction/evolution reactions, boosting the realistic rechargeable zinc-air batteries with high efficiency, low overpotential, and robust reversibility, superior to other counterparts and state-of-the-art precious-metal catalysts. Theoretical computations based on density functional theory demonstrate that the homogenously dispersed single atoms and the synergistic effect of neighboring Co-Ni dual metal center can optimize the adsorption/desorption features and decrease the overall reaction barriers, eventually promoting the reversible oxygen electrocatalysis. This work not only sheds light on the controlled synthesis of atomically isolated advanced materials, but also provides deeper understanding on the structure-performance relationships of nanocatalysts with multiple active sites for various catalytic applications.

Generation of Nanoparticle, Atomic-Cluster, and Single-Atom Cobalt Catalysts from Zeolitic Imidazole Frameworks by Spatial Isolation and Their Use in Zinc-Air Batteries.

The size effect of transition-metal nanoparticles on electrocatalytic performance remains ambiguous especially when decreasing the size to the atomic level. Herein, we report the spatial isolation of cobalt species on the atomic scale, which was achieved by tuning the zinc dopant content in predesigned bimetallic Zn/Co zeolitic imidazole frameworks (ZnCo-ZIFs), and led to the synthesis of nanoparticles, atomic clusters, and single atoms of Co catalysts on N-doped porous carbon. This synthetic strategy allowed an investigation of the size effect on electrochemical behavior from nanometer to Ångström dimensions. Single-atom Co catalysts showed superior bifunctional ORR/OER activity, durability, and reversibility in Zn-air batteries compared with the other derivatives and noble-metal Pt/C+RuO2 , which was attributed to the high reactivity and stability of isolated single Co atoms. Our findings open up a new avenue to regulate the metal particle size and catalytic performance of MOF derivatives.

Molecular mechanisms of tannin accumulation in Rhus galls and genes involved in plant-insect interactions.

For galling aphids and their hosts, tannins are crucial for plant-insect interactions and for protecting the host plant from herbivory. Due to their peculiar chemical characteristics, tannins from plant galls have been used for medical and chemical purposes for more than 2000 years. In this study, hydrolyzable tannin concentrations in galls increased from gall initiation (38.34% on June 21) to maturation (74.79% on August 8), then decreased gradually thereafter (58.83% on October 12). We identified a total of 81 genes (named as GTS1-81) with putative roles in gallotannin biosynthesis and 22 genes (TS1-22) in condensed tannin biosynthesis. We determined the expression profiles of these genes by real-time PCR over the course of gall development. Multiple genes encoding 1-beta-D-glucosyl transferases were identified, which may play a vital role in gallotannin accumulation in plant galls. This study is the first attempt to examine the molecular basis for the regulation of tannin accumulation in insect gallnuts. The differentially expressed genes we identified may play important roles in both tannin biosynthesis and plant-insect interactions.