Composition and Diversity of Gut Bacterial Community in Different Life Stages of a Leaf Beetle Gastrolina depressa.

Insect gut bacteria have a significant impact on host biology, which has a favorable or negative impact on insect fitness. The walnut leaf beetle (Gastrolina depressa) is a notorious pest in China, causing severe damage to Juglandaceae trees including Juglans regia and Pterocarya rhoifolia. To date, however, we know surprisingly little about the gut microbiota of G. depressa. This study used a high-throughput sequencing platform to investigate the gut bacterial community of G. depressa throughout its life cycle, including the 1st, 2nd, and 3rd instar larvae, as well as male, female, and pre-pregnant female adults. Our results showed that the diversity of the gut bacterial community in larvae was generally higher than that in adults, and young larvae (1st and 2nd larvae) possessed the most diversified and abundant community. Principal coordinate analysis results showed that the gut microbiota of adults cluster together, which is independent of the 1st and 2nd instar larvae. The main phyla were Proteobacteria and Firmicutes in the microbial community of G. depressa, while the dominant genera were Enterobacter, Rosenbergiella, Erwinia, Pseudomonas, and Lactococcus. The gut bacteria of G. depressa were mostly enriched in metabolic pathways (carbohydrate metabolism and amino acid metabolism) as revealed by functional prediction. This study contributes to a better knowledge of G. depressa's gut microbiota and its potential interactions with the host insect, facilitating the development of a microbial-based pest management strategy.

Dynamic Gut Microbiota of Apolygus lucorum Across Different Life Stages Reveals Potential Pathogenic Bacteria for Facilitating the Pest Management.

Insect's gut microbiota has diverse effects on their fitness, and a comprehensive understanding of gut microbiota functions requires analyzing its diversity. Apolygus lucorum is a highly destructive pest that threatens many economically important crops in China. This study investigated the gut microbiota of A. lucorum across its life cycle using both culture-dependent and culture-independent methods. A total of 87 gut bacterial isolates were identified, belonging to 4 phyla, 27 families, and 45 genera, while Miseq sequencing detected 91 amplicon sequence variants (ASVs) assigned to 5 phyla, 28 families, and 39 genera. Proteobacteria and Firmicutes were the predominant phyla, with Staphylococcus and Serratia as the major genera. There were significant differences in the relative abundance of these genera between the nymph and adult stages. Staphylococcus was significantly more abundant in nymphs than it in adults, while Serratia was significantly more abundant in sexually mature adults than in other developmental stages. Notably, Serratia is a common opportunistic pathogen in many insects. Injecting the gut-dominant isolate Serratia marcescens verified its high pathogenicity. Additionally, immune indicators of the bug at different developmental stages supported the hypothesis that Serratia is a pathogen of A. lucorum. This study provides a foundation for understanding the role of gut bacteria in the life history of A. lucorum and developing new pest control strategies based on microbes.

Gut bacterial microbiota of Lymantria dispar asiatica and its involvement in Beauveria bassiana infection.

The gut bacterial microbiota of insects has been shown to play essential roles in processes related to physiology, metabolism, and innate immunity. In this study, we firstly performed a broad analysis of the gut bacteria in Lymantria dispar asiatica, one of the most devastating forestry defoliators. We analyzed the bacterial composition among different individuals from lab-reared or wild-collected using 16 s rRNA-sequencing, revealing that the gut bacteria of wild-collected larvae were highly diverse, while lab-reared larvae were only associated with a few genera. We found Lactobacillus sp. present in all the gut samples, which indicates that it is part of the core microbiome in the caterpillar. Further Beauveria bassiana infection-based assays showed that the mortality of non-axenic L. dispar asiatica larvae was significantly higher than that of axenic larvae at 72 h. Moreover, we isolated several bacteria from the hemolymph of the non-axenic larvae infected by B. bassiana, which may be caused by the translocation of gut bacteria from the gut to the hemocoel. Reintroduction of Enterococcus sp., Pseudomonas sp., Enterobacter sp., and Microbacterium sp. into axenic larvae recurred the larval mortality in their non-axenic counterpart. Taken together, our study demonstrates that the gut bacteria of L. dispar asiatica are highly volatile, and different bacteria taxa can promote host infection by entomopathogenic fungus, providing a new strategy for the pest management.

Enhanced toxicity of entomopathogenic fungi Beauveria bassiana with bacteria expressing immune suppressive dsRNA in a leaf beetle.

The entomopathogenic fungus is recognized as an ideal alternative to chemical pesticides, nonetheless, its efficacy is often limited by insect's innate immune system. The suppression of the host immunity may overcome the obstacle and promote the toxicity of the fungi. Here, by using an entomopathogenic fungus Beauveria bassiana and immune genes dsRNA-expressing bacteria, we explored the potentially synergistic toxicity of the two agents on a leaf beetle Plagiodera versicolora (Coleoptera: Chrysomelidae). We first determined the susceptibilities of P. versicolora to a B. bassiana 476 strain (hereafter referred to Bb476). And the immune genes were identified based on the transcriptome of Bb476 challenged beetles. Subsequently, five immune genes (PGRP1, Toll1, Domeless，SPN1，and Lysozyme) were targeted by feeding dsRNA-expressing bacteria, which produced a 71.4, 39.0, 72.0, 49.0, and 68.7% gene silencing effect, respectively. Furthermore, we found a significantly increased mortality of P. versicolora when combined the Bb476 and the immune suppressive dsRNAs. Taking together, this study highlights the importance of insect immunity in the defense of entomopathogens and also paves the way toward the development of a more efficient pest management strategy that integrates both entomopathogens and immune suppressive dsRNAs.

Efficient Circularly Polarized Electroluminescence from Achiral Luminescent Materials.

Circularly polarized electroluminescence (CP-EL) is generally produced in organic light-emitting diodes (OLEDs) based on special CP luminescent (CPL) materials, while common achiral luminescent materials are rarely considered to be capable of direct producing CP-EL. Herein, near ultraviolet CPL materials with high photoluminescence quantum yields and good CPL dissymmetry factors are developed, which can induce blue to red CPL for various achiral luminescent materials. Strong near ultraviolet CP-EL with the best external quantum efficiencies (ηext s) of 9.0 % and small efficiency roll-offs are achieved by using them as emitters for CP-OLEDs. By adopting them as hosts or sensitizers, commercially available yellow-orange achiral phosphorescence, thermally activated delayed fluorescence (TADF) and multi-resonance (MR) TADF materials can generate intense CP-EL, with high dissymmetry factors and outstanding ηext s (30.8 %), demonstrating a simple and universal avenue towards efficient CP-EL.

Isolation, Identification, and Analysis of Potential Functions of Culturable Bacteria Associated with an Invasive Gall Wasp, Leptocybe invasa.

Symbioses between invasive insects and bacteria are one of the key drivers of insect invasion success. Gall-inducing insects stimulate host plants to produce galls, which affects the normal growth of plants. Leptocybe invasa Fisher et La Salle, an invasive gall-inducing wasp, mainly damages Eucalyptus plantations in Southern China, but little is known about its associated bacteria. The aim of this study was to assess the diversity of bacterial communities at different developmental stages of L. invasa and to identify possible ecological functions of the associated bacteria. Bacteria associated with L. invasa were isolated using culture-dependent methods and their taxonomic statuses were determined by sequencing the 16S rRNA gene. A total of 88 species belonging to four phyla, 27 families, and 44 genera were identified by phylogenetic analysis. The four phyla were Proteobacteria, Actinobacteria, Firmicutes, and Bacteroidetes, mainly from the genera Pantoea, Enterobacter, Pseudomonas, Bacillus, Acinetobacter, Curtobacterium, Sphingobium, Klebsiella, and Rhizobium. Among them, 72 species were isolated in the insect gall stage and 46 species were isolated from the adult stage. The most abundant bacterial species were γ-Proteobacteria. We found significant differences in total bacterial counts and community compositions at different developmental stages, and identified possible ecological roles of L. invasa-associated bacteria. This study is the first to systematically investigate the associated bacteria of L. invasa using culture-dependent methods, and provides a reference for other gall-inducing insects and associated bacteria.

Comparative analysis of the immune system and expression profiling of Lymantria dispar infected by Beauveria bassiana.

Lymantria dispar is one of the most devastating forest pests worldwide. Fungal biopesticides have great potential as alternatives owing to their high lethality to pests and eco-friendly feature, which is, however, often severely compromised by the pests' innate immunity. A better understanding of the antifungal immune system in L. dispar would significantly facilitate the development of the biopesticide. Here, we investigated phylogenetic characteristics of immunity-related genes as well as the tissue expression patterns in L. dispar after the infection of an entomopathogen Beauveria bassiana using RNA-sequencing data. Results showed most immune genes remain at a low level of response after 24 h post-infection (HPI). Almost all genes in the Toll pathway were significantly up-regulated at 48 HPI, and SPH1, SPN6, Toll6, Toll12, Myd88, pelle, and Drosal were significantly down-regulated at 72 HPI. Immunoblotting analysis revealed that the protein levels of ßGRP3 and PPO1 were significantly upregulated at 24 and 48 HPI, while Myd88 was downregulated at 24 HPI, which was further confirmed by Quantitative real-time PCR experiments. Moreover, the relative content of H2O2, a potent reactive oxygen species (ROS), was significantly increased with the decrease of the total antioxidant capacity, indicating that oxidative stress system positively participates in the clearance of the pathogenic fungus. Together, our study provides detailed genetic characteristics of antifungal immunity as well as profiling of the host defense against entomopathogenic infection, and comprehensive insight into molecular interaction between L. dispar and the entomopathogen.

Phosphorescent Bismoviologens for Electrophosphorochromism and Visible Light-Induced Cross-Dehydrogenative Coupling.

A series of novel bismuth-bridged viologen analogues, bismoviologens (BiV2+), synthesized through a combination of a bismuth atom and viologen skeleton is reported. Their optical and electrochemical properties were fine-tuned through the N-arylation or N-alkylation reactions. Bismolviologens not only showed good redox properties but also exhibited phosphorescence under ambient conditions (in air at room temperature). This phenomenon makes BiV2+ the first examples of phosphorescent viologen analogues reported to date. On the basis of the excellent and unique redox and optical properties of BiV2+, their electrophosphorochromic devices were fabricated. Furthermore, BiV2+ was used for the first time as both a photocatalyst and electron mediator in visible light-induced cross-dehydrogenative coupling reactions.

Anti-Sandwich Structured Photo-Electronic Wound Dressing for Highly Efficient Bacterial Infection Therapy.

Photo-electronic devices based on reactive oxygen species (ROS) generation suffer a crucial limitation in wound treatment due to their sandwich structure, which prevents the contact of ROS with wound tissue. In this work, the first anti-sandwich structured visible-light/electricity dual-responsive wound dressing is constructed for treatment of methicillin-resistant Staphylococcus aureus (MRSA), based on selenoviologen-appendant polythiophene (SeV2+ -PT)-containing polyacrylamide hydrogels. The new wound dressing is named an anti-sandwich structured photo-electronic wound dressing (PEWD). The unique structure of PEWD enables its use in synergistic electrodynamic and photodynamic therapy (EDT and PDT), providing rapid, on-demand, and sustained generation of ROS in situ via short-time light irradiation and/or wireless-controlled electrification. The PEWD possesses good flexibility, excellent biocompatibility, and fast response, as well as sustained ROS generation in a physiological environment. Animal experiments demonstrate effective ROS generation in 6 s under irradiation and electrification, inhibiting infection at an early stage, and substantially shortening the healing time of bacterial infection (to within 7 days). This proof-of-concept research holds great promise in developing new flexible PEWD, and novel strategies to improve wound treatment.

Emissive Platinum(II) Cages with Reverse Fluorescence Resonance Energy Transfer for Multiple Sensing.

It is quite challenging to realize fluorescence resonance energy transfer (FRET) between two chromophores with specific positions and directions. Herein, through the self-assembly of two carefully selected fluorescent ligands via metal-coordination interactions, we prepared two tetragonal prismatic platinum(II) cages with a reverse FRET process between their faces and pillars. Bearing different responses to external stimuli, these two emissive ligands are able to tune the FRET process, thus making the cages sensitive to solvents, pressure, and temperature. First, these cages could distinguish structurally similar alcohols such as n-butanol, t-butanol, and i-butanol. Furthermore, they showed decreased emission with bathochromic shifts under high pressure. Finally, they exhibited a remarkable ratiometric response to temperature over a wide range (223-353 K) with high sensitivity. For example, by plotting the ratio of the maximum emission (I600/I480) of metallacage 4b against the temperature, the slope reaches 0.072, which is among the highest values for ratiometric fluorescent thermometers reported so far. This work not only offers a strategy to manipulate the FRET efficiency in emissive supramolecular coordination complexes but also paves the way for the future design and preparation of smart emissive materials with external stimuli responsiveness.

Length-dependent accumulation of double-stranded RNAs in plastids affects RNA interference efficiency in the Colorado potato beetle.

Transplastomic potato plants expressing double-stranded RNA (dsRNA) targeted against essential genes of the Colorado potato beetle (CPB) can be lethal to larvae by triggering an RNA interference (RNAi) response. High accumulation levels of dsRNAs in plastids are crucial to confer an efficient RNAi response in the insects. However, whether length and sequence of the dsRNA determine the efficacy of RNAi and/or influence the level of dsRNA accumulation in plastids is not known. We compared the RNAi efficacy of different lengths of dsRNA targeted against the CPB ß-Actin gene (ACT) by feeding in vitro-synthesized dsRNAs to larvae. We showed that, while the 60 bp dsRNA induced only a relatively low RNAi response in CPB, dsRNAs of 200 bp and longer caused high mortality and similar larval growth retardation. When the dsRNAs were expressed from the plastid (chloroplast) genome of potato plants, we found that their accumulation were negatively correlated with length. The level of dsRNA accumulation was positively associated with the observed mortality, suppression of larval growth, and suppression of target gene expression. Importantly, transplastomic potato plants expressing the 200 bp dsRNA were better protected from CPB than plants expressing the 297 bp dsRNA, the best-performing line in our previous study. Our results suggest that the length of dsRNAs is an important factor that influences their accumulation in plastids and thus determines the strength of the insecticidal RNAi effect. Our findings will aid the design of optimized dsRNA expression constructs for plant protection by plastid-mediated RNAi.

Baseline Sensitivity and Toxic Action of the Sterol Demethylation Inhibitor Flusilazole Against Botrytis cinerea.

In the present study, a total of 95 Botrytis cinerea single-spore strains collected from different hosts in Shaanxi Province of China were characterized for their sensitivity to the sterol demethylation inhibitor fungicide flusilazole. The effective concentration for 50% inhibition of mycelial growth (EC50) of flusilazole ranged from 0.021 to 0.372 µg/ml, with an average value of 0.093 µg/ml. Cross-resistance between flusilazole and commonly used fungicides was not detected, and no flusilazole-resistant mutants were induced. Both on detached strawberry leaves and in greenhouse experiments, flusilazole was more effective than the commonly used fungicide carbendazim at reducing gray mold. After culture on PDA plates or detached strawberry leaves, no difference in sclerotia production or pathogenicity was detected between two strains, WG12 (most sensitive to flusilazole) and MX18 (least sensitive to flusilazole). After treatment with flusilazole, however, the two strains lost the ability to produce sclerotia, and oxalic acid and ergosterol contents in mycelium decreased. Interestingly, the inhibition rate of ergosterol content in MX18 was significantly lower than that in WG12. Expression of Cyp51, BcatrD, and Bcmfs1 genes all increased after treatment with flusilazole, especially the Cyp51 and BcatrD genes. However, the expression of Cyp51 gene or BcatrD gene in WG12 and MX18 were significantly different from each other after treatment with flusilazole. In addition, no point mutations in Cyp51 gene were found in MX18. These data suggest flusilazole is a promising fungicide for resistance management of gray mold and also provided novel insights into understanding the resistance mechanism of flusilazole against plant pathogens.

Cationic Chalcogenoviologen Derivatives for Photodynamic Antimicrobial Therapy and Skin Regeneration.

A series of water-soluble cationic chalcogenoviologen-based photosensitizers for photodynamic antimicrobial therapy (PDAT) is reported. The Se-containing derivatives (SeMV2+ ) 5 b and 6 b showed good antimicrobial activities due to the presence of chalcogen atoms and a cationic scaffold. The former efficiently enhanced the generation of reactive oxygen species (ROS), and the latter facilitated the ROS delivery to bacteria, resulting in their death. Interestingly, alkyl-modified photosensitizers showed higher antimicrobial activities than commonly reported photosensitizers with quaternary ammonium (QA) groups. In particular, the SeMV2+ (6 b) with excellent antibacterial activities efficiently promoted the healing of infected wounds in mice. Simple yet novel, nontoxic and biocompatible chalcogenoviologens provided a promising strategy to develop new efficient photosensitizers for photodynamic antimicrobial therapy and skin regeneration.

Self-Assembly of Macrocyclic Boronic Esters Bearing Tellurophene Moieties and Their Guest-Responsive Phosphorescence.

Guest-controlled diastereoselective self-assembly of a diboryltellurophene and a chiral tetrol bearing an indacene backbone was achieved to give either hetero- or homochiral macrocyclic boronic esters, selectively. The heterochiral isomer (hetero-[2+2]Te ) exhibited a higher inclusion ability for electron-deficient aromatic guests, leading to effective quenching of phosphorescence from the diboryltellurophene moieties. The reported macrocycles collectively represent a promising arene sensing approach based on phosphorescence.

A Modular Approach to Phosphorescent π-Extended Heteroacenes.

A modular route to previously inaccessible classes of ring-fused π-extended heteroacenes bearing the heavy inorganic element tellurium (Te) is presented. These new materials can be viewed as n-doped analogs of molecular graphene subunits that exhibit color tunable visible light phosphorescence in the solid state and in the presence of air. The general mechanism of phosphorescence in these systems was probed experimentally and computationally via time-dependent density functional theory (TD-DFT). The incorporation of Te into π-extended oligoacene frameworks was achieved by an efficient Zr/Te transmetalation protocol; related zirconium-element exchange reactions have been used to prepare both electron-rich and electron-deficient heterocycles containing different elements from throughout the p-block. Therefore, the current study provides a clear path to incorporate inorganic elements into heteroacenes of greater complexity and side group selectivity compared to existing synthetic routes.

Electrochromic Poly(chalcogenoviologen)s as Anode Materials for High-Performance Organic Radical Lithium-Ion Batteries.

A series of electrochromic electron-accepting poly(chalcogenoviologen)s with multiple, stable, and reversible redox centers were used as anodic materials in organic radical lithium-ion batteries (ORLIBs). The introduction of heavy atoms (S, Se, and Te) into the viologen scaffold significantly improved the capacity and cycling stability of the ORLIBs. Notably, the poly(Te-BnV) anode was able to intercalate 20 Li ions and showed higher conductivity and insolubility in the electrolyte, thus contributing to a reversible capacity of 502 mAh g-1 at 100 mA g-1 when the Coulombic efficiency approached 100 %. The charged/discharged state of flexible electrochromic batteries fabricated from these anodic materials could be monitored visually owing to the unique electrochromic and redox properties of the materials. This study opens a promising avenue for the development of organic polymer-based electrodes for flexible hybrid visual electronics.

Narrow-Bandgap Chalcogenoviologens for Electrochromism and Visible-Light-Driven Hydrogen Evolution.

A series of electron-accepting chalcogen-bridged viologens with narrow HOMO-LUMO bandgaps and low LUMO levels is reported. The optoelectronic properties of chalcogenoviologens can be readily tuned through heavy atom substitution (S, Se and Te). Herein, in situ electrochemical spectroscopy was performed on the proof-of-concept electrochromic devices (ECD). E-BnV2+ (E=Se, Te; BnV2+ =benzyl viologen) was used for the visible-light-driven hydrogen evolution due to the strong visible-light absorption. Remarkably, E-BnV2+ was not only used as a photosensitizer, but also as an electron mediator, providing a new strategy to explore photocatalysts. The higher apparent quantum yield of Se-BnV2+ could be interpreted in terms of different energy levels, faster electron-transfer rates and faster formation of radical species.

Aerobic Solid State Red Phosphorescence from Benzobismole Monomers and Patternable Self-Assembled Block Copolymers.

The synthesis of the first bismuth-containing macromolecules that exhibit phosphorescence in the solid state and in the presence of oxygen is reported. These red emissive high molecular weight polymers (>300 kDa) feature benzobismoles appended to a hydrocarbon scaffold, and were built via an efficient ring-opening metathesis (ROMP) protocol. Moreover, our general procedure readily allows for the formation of cross-linked networks and block copolymers. Attaining stable red phosphorescence with non-toxic elements remains a challenge and, thus, our new class of soluble (processable) polymeric phosphor is of great interest. Furthermore, the formation of bismuth-rich cores within organic-inorganic block copolymer spherical micelles is possible, leading to patterned arrays of bismuth in the film state.

Pine Defensive Monoterpene α-Pinene Influences the Feeding Behavior of Dendroctonus valens and Its Gut Bacterial Community Structure.

The exposure to plant defense chemicals has negative effects on insect feeding activity and modifies insect gut microbial community composition. Dendroctonus valens is a very destructive forest pest in China, and harbors a large diversity and abundance of gut microorganisms. Host pine defensive chemicals can protect the pines from attack by the holobiont. In this study, boring length of D. valens feeding on 0 mg/g α-pinene and 9 mg/g α-pinene concentration in phloem media for 6 and 48 h were recorded, and their gut bacterial communities were analyzed in parallel. Nine milligram per gram α-pinene concentration significantly inhibited boring length of D. valens and altered its gut microbial community structure after 6 h. The inhibition of boring length from 9 mg/g α-pinene in diets ceased after 48 h. No significant differences of the bacterial communities were observed between the beetles in 0 and 9 mg/g α-pinene concentration in phloem media after 48 h. Our results showed that the inhibition of the feeding behavior of D. valens and the disturbance to its gut bacterial communities in 9 mg/g α-pinene concentration in phloem media after 6 h were eliminated after 48 h. The resilience of gut bacterial community of D. valens may help the beetle catabolize pine defense chemical.

Gut-Associated Bacteria of Dendroctonus valens and their Involvement in Verbenone Production.

Bark beetles are the most important mortality agent in coniferous forests, and pheromones play important roles in their management. Dendroctonus valens LeConte was introduced from North America to China and has killed millions of healthy pines there. Trapping with semiochemicals and pheromones was deployed in D. valens management in the last decade, but little is known about the ability of gut bacteria to produce the pheromone. In this study, we analyzed the volatiles in D. valens guts and frass after antibiotic treatment versus control. Then, we isolated and identified the bacteria in D. valens guts and frass, examined verbenone (a multifunctional pheromone of D. valens) production by 16 gut bacterial isolates from the precursor cis-verbenol at three concentrations, and further compared the cytotoxicities between the cis-verbenol and verbenone to the bacterial isolates. cis-Verbenol was not detected in the frass in the control group, but it was in the antibiotic treatment. The amount of verbenone was significantly suppressed in D. valens guts after antibiotic treatment versus control. Thirteen out of 16 gut bacterial isolates were capable of cis-verbenol to verbenone conversion, and cis-verbenol had stronger cytotoxicities than verbenone to all tested gut bacterial isolates. The bacterial species capable of verbenone production largely exists in D. valens guts and frass, suggesting that gut-associated bacteria may help the bark beetle produce the pheromone verbenone in guts and frass. The bacteria may benefit from the conversion due to the reduced cytotoxicity from the precursor to the beetle pheromone.