Metabarcoding read abundances of orchid mycorrhizal fungi are correlated to copy numbers estimated using ddPCR.

Quantifying the abundances of fungi is key to understanding natural variation in mycorrhizal communities in relation to plant ecophysiology and environmental heterogeneity. High-throughput metabarcoding approaches have transformed our ability to characterize and compare complex mycorrhizal communities. However, it remains unclear how well metabarcoding read counts correlate with actual read abundances in the sample, potentially limiting their use as a proxy for species abundances. Here, we use droplet digital PCR (ddPCR) to evaluate the reliability of ITS2 metabarcoding data for quantitative assessments of mycorrhizal communities in the orchid species Neottia ovata sampled at multiple sites. We performed specific ddPCR assays for eight families of orchid mycorrhizal fungi and compared the results with read counts obtained from metabarcoding. Our results demonstrate a significant correlation between DNA copy numbers measured by ddPCR assays and metabarcoding read counts of major mycorrhizal partners of N. ovata, highlighting the usefulness of metabarcoding for quantifying the abundance of orchid mycorrhizal fungi. Yet, the levels of correlation between the two methods and the numbers of false zero values varied across fungal families, which warrants cautious evaluation of the reliability of low-abundance families. This study underscores the potential of metabarcoding data for more quantitative analyses of mycorrhizal communities and presents practical workflows for metabarcoding and ddPCR to achieve a more comprehensive understanding of orchid mycorrhizal communities.

Novel insights into orchid mycorrhiza functioning from stable isotope signatures of fungal pelotons.

Stable isotope signatures of fungal sporocarps have been instrumental in identifying carbon gains of chlorophyllous orchids from a fungal source. Yet, not all mycorrhizal fungi produce macroscopic sporocarps and frequently fungi of different taxa occur in parallel in orchid roots. To overcome this obstacle, we investigated stable isotope signatures of fungal pelotons extracted from orchid roots and compared these data to the respective orchid and reference plant tissues. Anoectochilus sandvicensis and Epipactis palustris represented specialized or unspecialized rhizoctonia-associated orchids. Epipactis atrorubens and Epipactis leptochila are orchids considered ectomycorrhiza-associated with different preferences for Basidio- and Ascomycota. 13 C enrichment of rhizoctonia pelotons was minor compared with plant tissues and significantly lower than enrichments of pelotons from ectomycorrhizal Epipactis species. 15 N values of pelotons from E. leptochila and E. atrorubens showed similar patterns as known for respective sporocarps of ectomycorrhizal Ascomycota and Basidiomycota, however, with an offset towards lower 15 N enrichments and nitrogen concentrations. Our results suggest an explicit fungal nutrition source of orchids associated with ectomycorrhizal fungi, whereas the low 13 C enrichment in rhizoctonia-associated orchids and fungal pelotons hamper the detection of carbon gains from fungal partners. 15 N isotopic pattern of orchids further suggests a selective transfer of 15 N-enriched protein-nitrogen into orchids.

Symbiont switching and trophic mode shifts in Orchidaceae.

Mycorrhizal fungi are central to the biology of land plants. However, to what extent mycorrhizal shifts - broad evolutionary transitions in root-associated fungal symbionts - are related to changes in plant trophic modes remains poorly understood. We built a comprehensive DNA dataset of Orchidaceae fungal symbionts and a dated plant molecular phylogeny to test the hypothesis that shifts in orchid trophic modes follow a stepwise pattern, from autotrophy over partial mycoheterotrophy (mixotrophy) to full mycoheterotrophy, and that these shifts are accompanied by switches in fungal symbionts. We estimate that at least 17 independent shifts from autotrophy towards full mycoheterotrophy occurred in orchids, mostly through an intermediate state of partial mycoheterotrophy. A wide range of fungal partners was inferred to occur in the roots of the common ancestor of this family, including 'rhizoctonias', ectomycorrhizal, and wood- or litter-decaying saprotrophic fungi. Phylogenetic hypothesis tests further show that associations with ectomycorrhizal or saprotrophic fungi were most likely a prerequisite for evolutionary shifts towards full mycoheterotrophy. We show that shifts in trophic mode often coincided with switches in fungal symbionts, suggesting that the loss of photosynthesis selects for different fungal communities in orchids. We conclude that changes in symbiotic associations and ecophysiological traits are tightly correlated throughout the diversification of orchids.

Spatial inhomogeneity, interfaces and complex vitrification kinetics in a network forming nanocomposite.

A detailed calorimetric study on an epoxy-based nanocomposite system was performed employing bisphenol A diglycidyl ether (DGEBA) cured with diethylenetriamine (DETA) as the polymer matrix and a taurine-modified MgAL layered double hydroxide (T-LDH) as the nanofiller. The -NH2 group of taurine can react with DGEBA improving the interaction of the polymer with the filler. The combined X-ray scattering and electron microscopy data showed that the nanocomposite has a partially exfoliated morphology. Calorimetric studies were performed using conventional DSC, temperature modulated DSC (TMDSC) and fast scanning calorimetry (FSC) in the temperature modulated approach (TMFSC) to investigate the vitrification and molecular mobility dependent on the filler concentration. First, TMDSC and NMR were used to estimate the amount of the rigid amorphous fraction which consists of immobilized polymer segments at the nanoparticle surface. It was found to be 40 wt% for the highest filler concentration, indicating that the interface dominates the overall macroscopic properties and behavior of the material to a great extent. Second, the relaxation rates of the α-relaxation obtained by TMDSC and TMFSC were compared with the thermal and dielectric relaxation rates measured by static FSC. The investigation revealed that the system shows two distinct α-relaxation processes. Furthermore, two separate vitrification mechanisms were also found for a bulk network-former without geometrical confinement as also confirmed by NMR. This was discussed in terms of the intrinsic spatial heterogeneity on a molecular scale, which becomes more pronounced with increasing nanofiller content.

Highly efficient BiVO4single-crystal nanosheets with dual modification: phosphorus doping and selective Ag modification.

BiVO4, a visible-light response photocatalyst, has shown tremendous potential because of abundant raw material sources, good stability and low cost. There exist some limitations for further applicaitions due to poor capability to separate electron-hole pairs. In fact, a single-component modification strategy is barely adequate to obtain highly efficient photocatalytic performance. In this work, P substituted some of the V atoms from VO4oxoanions, namely P was doped into the V sites in the host lattice of BiVO4by a hydrothermal route. Meanwhile, Ag as an attractive and efficient electron-cocatalyst was selectively modified on the (010) facet of BiVO4nanosheets via facile photo-deposition. As a result, the obtained dually modified BiVO4sheets exhibited enhanced photocatalytic degradation property of methylene blue (MB). In detail, photocatalytic rate constant (k) was 2.285 min-1g-1, which was 2.78 times higher than pristine BiVO4nanosheets. Actually, P-doping favored the formation of O vacancies, led to more charge carriers, and facilitated photocatalytic reaction. On the other hand, metallic Ag loaded on (010) facet effectively transferred photogenerated electrons, which consequently helped electron-hole pairs separation. The present work may enlighten new thoughts for smart design and controllable synthesis of highly efficient photocatalytic materials.

Nanocarbon-Based Flame Retardant Polymer Nanocomposites.

In recent years, nanocarbon materials have attracted the interest of researchers due to their excellent properties. Nanocarbon-based flame retardant polymer composites have enhanced thermal stability and mechanical properties compared with traditional flame retardant composites. In this article, the unique structural features of nanocarbon-based materials and their use in flame retardant polymeric materials are initially introduced. Afterwards, the flame retardant mechanism of nanocarbon materials is described. The main discussions include material components such as graphene, carbon nanotubes, fullerene (in preparing resins), elastomers, plastics, foams, fabrics, and film-matrix materials. Furthermore, the flame retardant properties of carbon nanomaterials and their modified products are summarized. Carbon nanomaterials not only play the role of a flame retardant in composites, but also play an important role in many aspects such as mechanical reinforcement. Finally, the opportunities and challenges for future development of carbon nanomaterials in flame-retardant polymeric materials are briefly discussed.

Bioinspired growth of iron derivatives on mesoporous silica: effect on thermal degradation and fire behavior of polystyrene.

Aiming to investigate the influence of pore property of mesoporous material on thermal degradation and fire behavior of polystyrene (PS), the ultrafine iron derivatives were uniformly grown on the interior wall of SBA-15 via the coordination-induced assembly by bioinspired polydopamine (PDA). The resultant SBA-15@PDA@Fe was verified by various characterizations with the dominant component of FeOOH. Compared with PS composites with SBA-15, PS composites with SBA-15@PDA@Fe revealed the notably divergent alteration in thermal and thermal-oxidation degradation behavior, which was determined by the changed pore property. The iron derivatives in SBA-15 mesopores possessed the stronger affinity to aerobic volatiles than anaerobic volatiles (via π-π coordination), which inhibited the release of oxidatively decomposed products and enhanced thermal-oxidation stability. In addition, SBA-15@PDA@Fe was capable to preferentially improve limiting oxygen index, accompanied by the decrease of smoke production through suppressing smoke precursors. The glass transition temperature (T g) of PS/SBA-15 was slightly increased via the bioinspired modification.

Evolution of plastid genomes of Holcoglossum (Orchidaceae) with recent radiation.

BACKGROUND: The plastid is a semiautonomous organelle with its own genome. Plastid genomes have been widely used as models for studying phylogeny, speciation and adaptive evolution. However, most studies focus on comparisons of plastid genome evolution at high taxonomic levels, and comparative studies of the process of plastome evolution at the infrageneric or intraspecific level remain elusive. Holcoglossum is a small genus of Orchidaceae, consisting of approximately 20 species of recent radiation. This made it an ideal group to explore the plastome mutation mode at the infrageneric or intraspecific level. RESULTS: In this paper, we reported 15 complete plastid genomes from 12 species of Holcoglossum and 1 species of Vanda. The plastid genomes of Holcoglossum have a total length range between 145 kb and 148 kb, encoding a set of 102 genes. The whole set of ndh-gene families in Holcoglossum have been truncated or pseudogenized. Hairpin inversion in the coding region of the plastid gene ycf2 has been found. CONCLUSIONS: Using a comprehensive comparative plastome analysis, we found that all the indels between different individuals of the same species resulted from the copy number variation of the short repeat sequence, which may be caused by replication slippage. Annotation of tandem repeats shows that the variation introduced by tandem repeats is widespread in plastid genomes. The hairpin inversion found in the plastid gene ycf2 occurred randomly in the Orchidaceae.

Polar tube structure and three polar tube proteins identified from Nosema pernyi.

Microsporidian spores contain a single polar filament that is coiled around the interior of the spore. Upon germination the polar tube (post-germination polar filament) is ejected by inversion into a host cell. The sporoplasm flows through the polar tube, directly infecting the cytoplasm of the cell. Various species of microsporidia display differences in the number of coils in the polar filament and in the amino acid sequence of the polar tube proteins (PTPs). Nosema pernyi is a lethal pathogen that causes microsporidiosis in the Chinese oak silkworm, Antheraea pernyi. In this study, we identified three PTPs in N. pernyi using RT-PCR and LC-MS/MS. Polar tube protein 3 was localized in the polar tube using immuno-histochemical staining and an immunofluorescence assay. Co-immunoprecipitation data and LC-MS/MS analysis revealed that some potential proteins, like immune related proteins in A. pernyi may interact with PTP3.

Peptidoglycan recognition proteins regulate immune response of Antheraea pernyi in different ways.

Peptidoglycan recognition proteins (PGRPs) are evolutionarily conserved molecules that act in innate immune responses against invading pathogens. Insect PGRPs activate the Toll and/or immune deficiency (IMD) signal transduction pathways. They induce cellular and humoral immune defense reactions that effectively protect insects from invasion of microorganisms. In this study, four cDNA clones encoding PGRPs (ApPGRP-A, ApPGRP-B, ApPGRP-C, ApPGRP-LE) were isolated from the Chinese oak silkworm, Antheraea pernyi. The deduced amino acid sequences of ApPGRP-B and -C share high identity with enzymatically active PGRP proteins and contain the amino acids required for amidase activity. The spatiotemporal expression patterns of ApPGRPs and their response to immune stimulations were determined, and suggest that PGRPs might act as a broad-spectrum pattern recognition protein and participate in the pathway activation system. Here, using an RNA-interference approach, we examined the function of PGRPs in response to immune stimulation. We observed that RNAi-mediated silencing of ApPGRP-A decreased the tested antimicrobial peptides (Attacin, Attacin 2, Ceropin, Gloverin, lysozyme and Lebocin) in response to Enterococcus pernyi challenge. However, reducing the ApPGRP-B, -C mRNA levels led to a strong increase of the AMP genes (except for Lebocin). These results suggest that ApPGRPs are necessary for pathway initiation complex formation and activate AMP generation. Our data also indicated that PGRP-B and -C down-regulate AMPs generation in the immune response.

Morphological characterization and HSP70-, IGS-based phylogenetic analysis of two microsporidian parasites isolated from Antheraea pernyi.

Two microsporidian isolates were extracted from single infected egg-laying tussah silk moth (Antheraea pernyi) in Liaoning Province, China. The microsporidia were subsequently grown in silk moth larvae, isolated, and subjected to morphological characterization (by light and transmission electron microscopy) and phylogenetic analysis (based on conserved genes). One type of spore was long-axis-oval in shape, measuring 4.71 × 1.95 µm, and the other type was short-axis-oval, measuring 3.64 × 2.17 µm. These dimensions were markedly different from those reported in the spores of the common microsporidia infecting A. pernyi, namely, Nosema pernyi (4.36 × 1.49 µm). A neighbor-joining phylogenetic tree based on HSP70 indicated that these microsporidia belonged to Nosema species and were closely related with Nosema bombycis and Nosema ceranae. Furthermore, in the phylogenetic tree based on the intergenic spacer (IGS) region, the long-axis-oval isolates were closely related and tended to form a clade away from the short-axis-oval isolates and N. pernyi isolates. The microsporidia isolated from A. pernyi clustered in one group. Nosema bombycis, Nosema spodopterae, and Endoreticulatus spp. appeared to be genetically distant from N. pernyi. The two isolates from A. pernyi fell in the Nosema group, but their spores differed from those of the spores of the common A. pernyi parasite N. pernyi, both in morphological and genetic aspects. The two isolates were designated Nosema sp. Ap (L) and Nosema sp. Ap (S). IGS was found to be informative in ascertaining phylogenetic relationships among species, and even closely related strains, of microsporidia.

Elaboration of Thermally Performing Polyurethane Foams, Based on Biopolyols, with Thermal Insulating Applications.

In this work, biobased rigid polyurethane foams (PUFs) were developed with the aim of achieving thermal and fireproofing properties that can compete with those of the commercially available products. First, the synthesis of a biopolyol from a wood residue by means of a scaled-up process with suitable yield and reaction conditions was carried out. This biopolyol was able to substitute completely the synthetic polyols that are typically employed within a polyurethane formulation. Different formulations were developed to assess the effect of two flame retardants, namely, polyhedral oligomeric silsesquioxane (POSS) and amino polyphosphate (APP), in terms of their thermal properties and degradation and their fireproofing mechanism. The structure and the thermal degradation of the different formulations was evaluated via Fourier Transformed Infrared Spectroscopy (FTIR) and thermogravimetric analysis (TGA). Likewise, the performance of the different PUF formulations was studied and compared to that of an industrial PUF. From these results, it can be highlighted that the addition of the flame retardants into the formulation showed an improvement in the results of the UL-94 vertical burning test and the LOI. Moreover, the fireproofing performance of the biobased formulations was comparable to that of the industrial one. In addition to that, it can be remarked that the biobased formulations displayed an excellent performance as thermal insulators (0.02371-0.02149 W·m-1·K-1), which was even slightly higher than that of the industrial one.

The cellular response and molecular mechanism of superoxide dismutase interacting with superparamagnetic iron oxide nanoparticles.

This study explored the response of superoxide dismutase (SOD) under superparamagnetic iron oxide nanoparticles (SPIONs)-induced oxidative stress using combined cellular and molecular methods. Results found that SPIONs induced the inhibition of catalase activity, the U-inverted change of SOD activity and the accumulation of reactive oxygen species (ROS), leading to oxidative damage and cytotoxicity. The change of intracellular SOD activity was resulted from the increase of molecular activity induced by directly interacting with SPIONs and ROS-inhibition of activity. The increase of molecular activity could be attributed to the structural and conformational changes of SOD, which were caused by the direct interaction of SOD with SPIONs. The SOD-SPIONs interaction and its interacting mechanism were explored by multi-spectroscopy, isothermal titration calorimetry and zeta potential assays. SOD binds to SPIONs majorly via hydrophobic forces with the involvement of electrostatic forces. SPIONs approximately adsorb 11 units of SOD molecule with the binding affinity of 2.99 × 106 M-1. The binding sites on SOD were located around Tyr residues, whose hydrophilicity increased upon interacting with SPIONs. The binding to SPIONs loosened the peptide chains, changed the secondary structure and reduced the aggregation state of SOD.

Bio-based epoxy vitrimer with inherent excellent flame retardance and recyclability via molecular design.

The development of biobased fire-safe thermosets with recyclability heralds the switch for a transition towards a circular economy. In this framework, we introduced a novel high-performance bio-epoxy vitrimer (named GVD), which was fabricated by forming a crosslinking network between bio-epoxy glycerol triglycidyl ether (Gte), varying amounts of reactive flame-retardant agent 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) (0-7 wt%) and a vanillin-based hardener (VA) with imine bonds. For instance, the epoxy vitrimer GVD5, featuring a DOPO content of 5 wt%, achieved a V-0 rating in the vertical burning test (UL-94) and obtained a limiting oxygen index (LOI) value of 31 %, surpassing the performance of pristine epoxy. Furthermore, the peak heat release rate and total heat release of GVD5 were reduced by 38.2 % and 26.3 %, respectively, compared to pristine epoxy. The GVD vitrimers further demonstrated exceptional reprocessability and recyclability, attributed to the presence of dynamic imine bonds within the topological crosslinking network. Remarkably, the epoxy vitrimers maintained the mechanical properties of the parent epoxy. Therefore, this work provides a facile strategy for fabricating high-performance and multi-functional bio-epoxy thermosets.

Exploiting Waste towards More Sustainable Flame-Retardant Solutions for Polymers: A Review.

The development of sustainable flame retardants is gaining momentum due to their enhanced safety attributes and environmental compatibility. One effective strategy is to use waste materials as a primary source of chemical components, which can help mitigate environmental issues associated with traditional flame retardants. This paper reviews recent research in flame retardancy for waste flame retardants, categorizing them based on waste types like industrial, food, and plant waste. The paper focuses on recent advancements in this area, focusing on their impact on the thermal stability, flame retardancy, smoke suppression, and mechanical properties of polymeric materials. The study also provides a summary of functionalization methodologies used and key factors involved in modifying polymer systems. Finally, their major challenges and prospects for the future are identified.

Cyclodextrin-based host-guest hierarchical fire retardants: Synthesis and novel strategy to endow polylactic acid fire retardancy and UV resistance.

ß-Cyclodextrin (ß-CD) with a cage-like supramolecular structure possesses the hydrophobic internal ring and external hydroxyl groups, which are beneficial for intramolecular interactions known as "host-guest" chemistry. This study presents a ß-CD-based three-functions-in-one and host-guest fire retardant (ßCD-MOF@Schiff base), which incorporates self-crosslinking Schiff base into its cavity and modification of its surface by metal-organic framework (MOF). With the presence of 5 wt% of ßCD-MOF@Schiff base, the LOI value of PLA composites increased to 29 % and showed 15 %, 17 % and 62 % reductions in peak heat release rate (pHRR), total heat release (THR), and the yield of hazard gas carbon monoxide, respectively. The mode action of FR on fire retardation of PLA showed that the FR promoted the char formation with higher thermal stability and graphitization, and modified the decomposition path of PLA. Additionally, the PLA composites exhibited enhanced UV resistance in the UVA and UVB areas with improved UV absorbance and the UPF values improving and doubling. This work develops a new approach to preparing biodegradable FR, which simultaneously endows fire safety and anti-UV properties for PLA.

Mycoheterotrophy in the wood-wide web.

The prevalence and potential functions of common mycorrhizal networks, or the 'wood-wide web', resulting from the simultaneous interaction of mycorrhizal fungi and roots of different neighbouring plants have been increasingly capturing the interest of science and society, sometimes leading to hyperbole and misinterpretation. Several recent reviews conclude that popular claims regarding the widespread nature of these networks in forests and their role in the transfer of resources and information between plants lack evidence. Here we argue that mycoheterotrophic plants associated with ectomycorrhizal or arbuscular mycorrhizal fungi require resource transfer through common mycorrhizal networks and thus are natural evidence for the occurrence and function of these networks, offering a largely overlooked window into this methodologically challenging underground phenomenon. The wide evolutionary and geographic distribution of mycoheterotrophs and their interactions with a broad phylogenetic range of mycorrhizal fungi indicate that common mycorrhizal networks are prevalent, particularly in forests, and result in net carbon transfer among diverse plants through shared mycorrhizal fungi. On the basis of the available scientific evidence, we propose a continuum of carbon transfer options within common mycorrhizal networks, and we discuss how knowledge on the biology of mycoheterotrophic plants can be instrumental for the study of mycorrhizal-mediated transfers between plants.

Multifunctional polylactic acid sensing fabric based on biomass flame retardants for intelligent fire early-warning.

Today, building materials emit many hazardous gases in the event of a fire, causing great harm to human health and the environment. Therefore, it is of great significance to develop bio-based flame retardant materials and to realize preventive measures to reduce fires or their damage. In this work, we fabricated a novel multifunctional fire early-warning polylactic acid-based fabric (MFR-PBF) by coating MXene nanosheet, phytic acid @ furfurylamine (PA@FA) and ammonium polyphosphate (APP) via an eco-friendly layer-by-layer assembly method. MFR-PBF showed outstanding flame retardancy including a limiting oxygen index value of 35 % and better char formation capacity. More importantly, MFR-PBF exhibited sensitive fire early-warning capability (∼1 s) and excellent cyclic alarm stability (>15 cycles) due to the excellent semiconductor responsiveness (light and heat) and the significant catalytic char formation effect. Moreover, MFR-PBF is comfortable, flexible and strong enough to sew onto firefighter uniform to detect a variety of human motions, which can be monitored in the internet by using a LoRa emitter and a gateway. In addition, the controllable heating performance rendered MFR-PBF as a potential portable heater. This work provides new insights into the preparation and application of intelligent fire early-warning fabrics in the smart fire protection and Internet of Things.

Recent Progress on Multifunctional Thermally Conductive Epoxy Composite.

In last years, the requirements for materials and devices have increased exponentially. Greater competitiveness; cost and weight reduction for structural materials; greater power density for electronic devices; higher design versatility; materials customizing and tailoring; lower energy consumption during the manufacturing, transport, and use; among others, are some of the most common market demands. A higher operational efficiency together with long service life claimed. Particularly, high thermally conductive in epoxy resins is an important requirement for numerous applications, including energy and electrical and electronic industry. Over time, these materials have evolved from traditional single-function to multifunctional materials to satisfy the increasing demands of applications. Considering the complex application contexts, this review aims to provide insight into the present state of the art and future challenges of thermally conductive epoxy composites with various functionalities. Firstly, the basic theory of thermally conductive epoxy composites is summarized. Secondly, the review provides a comprehensive description of five types of multifunctional thermally conductive epoxy composites, including their fabrication methods and specific behavior. Furthermore, the key technical problems are proposed, and the major challenges to developing multifunctional thermally conductive epoxy composites are presented. Ultimately, the purpose of this review is to provide guidance and inspiration for the development of multifunctional thermally conductive epoxy composites to meet the increasing demands of the next generation of materials.

Size-focused conservation may fail to protect the world's oldest trees.

Old trees are irreplaceable natural resources that provide multifaceted benefits to humans. Current conservation strategies focus primarily on large-sized trees that were often considered old. However, some studies have demonstrated that small trees can be more than thousands of years old, suggesting that conventional size-focused perceptions may hamper the efficiency of current conservation strategies for old trees. Here, we compiled paired age and diameter data using tree-ring records sampled from 121,918 trees from 269 species around the world to detect whether tree size is a strong predictor of age for old trees and whether the spatial distribution of small old trees differs from that of large old trees. We found that tree size was a weak predictor of age for old trees, and diameter explained only 10% of the total age variance of old trees. Unlike large-sized trees that are mainly in warm, wet environments and protected, small old trees are predominantly in cold, dry environments and mostly unprotected, indicating that size-focused conservation failed to protect some of the oldest trees. To conserve old trees, comprehensive old-tree recognition systems are needed that consider not only tree size but also age and external characteristics. Protected areas designed for small old trees are urgently needed.