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Tyrosinase catalyzes the oxidation of phenols and catechols (o-diphenols) to o-quinones. The reactivities of o-quinones thus generated are responsible for oxidative browning of plant products, sclerotization of insect cuticle, defense reaction in arthropods, tunichrome biochemistry in tunicates, production of mussel glue, and most importantly melanin biosynthesis in all organisms. These reactions also form a set of major reactions that are of nonenzymatic origin in nature. In this review, we summarized the chemical fates of o-quinones. Many of the reactions of o-quinones proceed extremely fast with a half-life of less than a second. As a result, the corresponding quinone production can only be detected through rapid scanning spectrophotometry. Michael-1,6-addition with thiols, intramolecular cyclization reaction with side chain amino groups, and the redox regeneration to original catechol represent some of the fast reactions exhibited by o-quinones, while, nucleophilic addition of carboxyl group, alcoholic group, and water are mostly slow reactions. A variety of catecholamines also exhibit side chain desaturation through tautomeric quinone methide formation. Therefore, quinone methide tautomers also play a pivotal role in the fate of numerous o-quinones. Armed with such wide and dangerous reactivity, o-quinones are capable of modifying the structure of important cellular components especially proteins and DNA and causing severe cytotoxicity and carcinogenic effects. The reactivities of different o-quinones involved in these processes along with special emphasis on mechanism of melanogenesis are discussed.

Animals synthesize melanin pigments for the coloration of their skin and use it for their protection from harmful solar radiation. Insects use melanins even more ingeniously than mammals and employ them for exoskeletal pigmentation, cuticular hardening, wound healing and innate immune responses. In this review, we discuss the biochemistry of melanogenesis process occurring in higher animals and insects. A special attention is given to number of aspects that are not previously brought to light: (1) the molecular mechanism of dopachrome conversion that leads to the production of two different dihydroxyindoles; (2) the role of catecholamine derivatives other than dopa in melanin production in animals; (3) the critical parts played by various biosynthetic enzymes associated with insect melanogenesis; and (4) the presence of a number of important gaps in both melanogenic and sclerotinogenic pathways. Additionally, importance of the melanogenic process in insect physiology especially in the sclerotization of their exoskeleton, wound healing reactions and innate immune responses is highlighted. The comparative biochemistry of melanization with sclerotization is also discussed.

Insect life on earth is greatly diversified despite being exposed to several infectious agents due to their diverse habitats and ecological niche. One of the major factors responsible for their successful establishment is having a powerful innate immune system. The most common and effective method used by insects in recognizing pathogen and non-self-substances is the melanization process among others. The key enzyme involved in melanin biosynthesis is the copper containing humoral defense enzyme, phenoloxidase (PO). This review focused on understanding about PO and that had been in research for nearly a century. The review elaborates about evolutionary significance of PO in arthropods, its relationship with mammalian tyrosinases, various substrates, activators and inhibitors involved in the activation of phenoloxidase cascade, as it requires an integrated system of activation that vary among insect species. The enzyme also plays a vital role in insect immunity by involving in several other immune functions like sclerotization, wound healing, opsonization, encapsulation and nodule formation. Further, gene knock down or knock out of PO genes and inhibition of PO-melanization cascade by several mechanisms can also be considered as promising future alternative to control serious pests by making them highly susceptible to any targeted attack.

The insect cuticle exoskeleton is among the most abundant and versatile biological structures. During ontogeny, the cuticle undergoes extensive modification, enabling insects to adapt to a wide range of ecological niches. In contrast, cuticular remodelling is generally thought to cease after adult emergence, raising the question of how mature insects respond to damage to their exoskeleton. To address this fundamental issue, we used an interdisciplinary experimental approach combining biomechanics, quantitative image analysis and molecular biology to investigate the response of mature Locusta migratoria to cuticular injury. We show that deep tibial wounds penetrating the epidermis trigger a coordinated repair programme that integrates rapid sclerotization of the perilesional cuticle with the local deposition of newly synthesized, layered cuticle beneath the wound site. These structural responses are accompanied by a strong but transient reactivation of the developmental enzyme chitin synthase 1 and the induction of the antimicrobial peptide defensin 3 in the vicinity of the injury. In contrast, superficial injuries that do not reach the epidermis fail to elicit cuticle deposition and sclerotization. Together, our results demonstrate that mature insects retain the capacity to locally reactivate developmental cuticle pathways to restore exoskeletal integrity, thereby directly linking structural repair with immune activation.

Traditionally, insects collected for scientific purposes have been dried and pinned, or preserved in 70% ethanol. Both methods preserve taxonomically informative exoskeletal structures well but are suboptimal for preserving DNA for molecular biology. Highly concentrated ethanol (95–100%), preferred as a DNA preservative, has generally been assumed to make specimens brittle and prone to breaking. However, systematic studies on the correlation between ethanol concentration and specimen preservation are lacking. Here, we tested how preservative ethanol concentration in combination with different sample handling regimes affect the integrity of seven insect species representing four orders, and differing substantially in the level of sclerotization. After preservation and treatments (various levels of disturbance), we counted the number of appendages (legs, wings, antennae, or heads) that each specimen had lost. Additionally, we assessed the preservation of DNA after long-term storage by comparing the ratio of PCR amplicon copy numbers to an added artificial standard. We found that high ethanol concentrations indeed induce brittleness in insects. However, the magnitude and nature of the effect varied strikingly among species. In general, ethanol concentrations at or above 90% made the insects more brittle, but for species with robust, thicker exoskeletons, this did not translate to an increased loss of appendages. Neither freezing the samples nor drying the insects after immersion in ethanol had a negative effect on the retention of appendages. However, the morphology of the insects was severely damaged if they were allowed to dry. We also found that DNA preserves less well at lower ethanol concentrations when stored at room temperature for an extended period. However, the magnitude of the effect varies among species; the concentrations at which the number of COI amplicon copies relative to the standard was significantly decreased compared to 95% ethanol ranged from 90% to as low as 50%. While higher ethanol concentrations positively affect long-term DNA preservation, there is a clear trade-off between preserving insects for morphological examination and genetic analysis. The optimal ethanol concentration for the latter is detrimental for the former, and vice versa. These trade-offs need to be considered in large insect biodiversity surveys and other projects aiming to combine molecular work with traditional morphology-based characterization of collected specimens.

Integrating shape memory polymers into the device provides multifunctionality and recyclability. However, complex programming steps and the immutability of material properties hinder their applications. Here, inspired by the Buprestidae sclerotization process, linear long side chains are introduced into chiral liquid crystal elastomers (CLCEs), a class of polymeric photonic crystals, enhancing the phase transition tendency of the system. Through microphase separation between the more ordered structure (smectic and crystalline phases) and the primary chiral nematic (N*) phase, self-enhancement of the material is achieved at room temperature while retaining the selective reflection of the N* phase. Within 48 hours, the Young’s modulus increases by 1854%, and the strain energy density in the 0–100% strain range increases by 1533%. This induces a shape-color integrated memory effect which can be fully restored upon heating. Cyclic utilization of a single CLCE film is demonstrated through programming, achieving the memory of colorful shapes and high-fidelity textures. Furthermore, local regulation of microphase separation enables encrypted information writing and recycling. Programmable shape memory polymers are of interest for smart materials, meanwhile the integration of shape and color enriches the applications. Here the authors use chiral liquid crystal elastomers affording a shape and color changing material, with dynamic mechanical properties.

Abstract Insects have evolved numerous adaptations and colonized diverse terrestrial environments. Several polyneopterans, including dictyopterans (cockroaches and mantids) and locusts, have developed oothecae, but little is known about the molecular mechanism, physiological function, and evolutionary significance of ootheca formation. Here, we demonstrate that the cockroach asymmetric colleterial glands produce vitellogenins, proline-rich protein, and glycine-rich protein as major ootheca structural proteins (OSPs) that undergo sclerotization and melanization for ootheca formation through the cooperative protocatechuic acid pathway and dopachrome and dopaminechrome subpathway. Functionally, OSP sclerotization and melanization prevent eggs from losing water at warm and dry conditions, and thus effectively maintain embryo viability. Dictyopterans and locusts convergently evolved vitellogenins, apolipoprotein D, and laminins as OSPs, whereas within Dictyoptera, cockroaches and mantids independently developed glycine-rich protein and fibroins as OSPs. Highlighting the ecological-evolutionary importance, convergent ootheca formation represents a successful reproductive strategy in Polyneoptera that promoted the radiation and establishment of cockroaches, mantids, and locusts.

The production of overwintering eggs is a critical adaptation for winter survival among many insects. Melanization contributes to eggshell pigmentation and hardening, consequently enhancing resistance to environmental stress. The complex life cycle of the pea aphid ( Acyrthosiphon pisum ), a model hemipteran insect with remarkable reproductive capacity, involves cyclical parthenogenesis. It enables the production of black overwintering eggs that undergo obligate diapause to survive under unfavorable conditions. Laccase2 ( Lac2 ) is essential for cuticle sclerotization and pigmentation in other insects. We hypothesized that Lac2 plays a critical role in aphid eggshell pigmentation and survival during diapause. To test the hypothesis, we used CRISPR/Cas9 ribonucleoprotein microinjections and a novel Direct Parental CRISPR (DIPA-CRISPR) method to knockout Lac2 . In Lac2 knockout (KO) crispants (G0), pigment-less eggs correlated with induced indel rates. Additionally, eggshell pigmentation was completely lost in homozygous Lac2 knockouts, leading to embryonic lethality. Observation of late-stage embryos in KO diapause eggs suggested that lethality occurred during late embryogenesis or hatching. Furthermore, eggshell stiffness was significantly reduced in Lac2 KOs, highlighting the role of this gene in eggshell hardening. Moreover, fungal growth was observed in KO eggs. These findings reveal the essential roles of Lac2 in eggshell pigmentation, hardening, late embryonic development, hatching, and fungal protection, which are critical for pea aphid survival during overwintering diapause. This study also advances CRISPR/Cas9-mediated genome editing in pea aphids by addressing the challenges associated with their unique biology, including complex life cycles, obligatory diapause, bacterial endosymbiosis, inbreeding depression, and high nuclease activity. Our optimized protocol achieved efficient targeted mutagenesis and germline transmission, thereby generating stable KO lines. Additionally, we successfully applied DIPA-CRISPR to aphids by inducing mutations via adult oviparous female injections in fertilized eggs. These robust genome-editing protocols will facilitate functional studies in aphids, a key model for research on evolution, ecology, development, and agriculture.

This study conducts a comprehensive analysis and comparison of Bombyx mori cuticles across different developmental stages, ranging from larval to adult, utilizing advanced solid-state NMR techniques. The primary objective is to elucidate the underlying reasons for the contrasting hardness of adult cuticles and softness of larval cuticles. Notably, PXRD analysis reveals a prominent broad peak at 19.34°, indicating the predominantly amorphous nature of both larval and adult cuticles. Analysis of 13 C CP-MAS SSNMR spectra highlights an elevated proportion of phenoxy carbon in adult cuticles (6.77%) compared to larval cuticles (1.24%). Furthermore, a distinctive resonance line at 144 ppm is exclusively observed in adult cuticles, due to catechols, suggesting potential biochemical pathway variations during development. Significant variations in the primary components of 13 C chemical shift anisotropy (CSA) tensors for aliphatic carbons of amino acids, catechols, and lipids between adult and larval cuticles indicate alterations in electronic environments. Additionally, the shorter spin–lattice relaxation time of carbon nuclei in larval cuticles compared to adult cuticles implies slower motional dynamics with enhanced degree of sclerotization in adults. By investigating the internal structure and dynamics of cuticles, this research not only contributes to biomimetic material development but also enhances our understanding of structural changes across different developmental stages of B. mori .

How parasites interact with their hosts at the molecular level is a central question in parasitology, yet identifying host pathways directly targeted by parasites is challenging because infections often have broad effects on host physiology. This difficulty is particularly pronounced in non-model systems, such as the interaction between the parasitic tapeworm Anomotaenia brevis and its intermediate host, the ant Temnothorax nylanderi , in which infection induces strong phenotypic changes. Here, we integrated host and parasite transcriptomes through a combined weighted gene co-expression network analysis (WGCNA) to identify candidate genes and gene networks involved in this interaction. We detected strong negative correlations between parasite and host gene expression, whereas within-species associations were largely positive. Candidate parasite genes were associated with host molecular pathways relevant to infection and host phenotype. The gene networks and expression correlations identified were consistent with those described in model parasite–host systems, supporting the robustness of our approach. Besides, our analysis provided initial functional insights into previously unannotated parasite proteins that may act as effectors of host manipulation. Expression of these parasite genes was correlated with host genes involved in oxidative stress resistance, metabolism, muscle function, immunity, and cuticular sclerotization. These associations suggest that the parasite may modulate multiple host pathways to facilitate infection and transmission. Overall, our findings advance our understanding of molecular mechanisms underlying parasite interference and highlight the value of integrating host and parasite transcriptomic data. More generally, our combined WGCNA framework provides a useful tool for uncovering transcriptional interactions in complex host–parasite systems.