Histiogaster arborsignis Woodring, 1963 (Acari: Acaridae) is a fungivorous acarid mite whose phoretic deutonymphs commonly disperse on wood-boring insects. Although the mite has been reported from Ips typographus in Germany, its occurrence in Central Europe has been poorly documented. Here, we report the first confirmed record of H. arborsignis associated with the Eurasian spruce bark beetle I. typographus in the Czech Republic and provide new evidence of its ecological roles within bark beetle gallery systems. Deutonymphs carried abundant adherent fungal propagules and transferred viable spores to PDA medium, from which the entomopathogenic fungus Beauveria bassiana (Balsamo-Crivelli, 1835) Vuillemin, 1912 was isolated and identified using multilocus DNA barcoding (ITS, TEF1-alpha, RPB1). The taxonomic identity of the mite was confirmed by morphology and COI sequencing. Laboratory observations showed that deutonymphs successfully moulted to adults in the presence of fungal colonies and interacted closely with mycelium, indicating the use of fungi as a developmental and nutritional resource. Feeding trials further revealed that adults actively attacked and consumed larvae and pupae of I. typographus within 24 hours, leaving only chitinised remains. Together, these results demonstrate that H. arborsignis is not merely a passive phoretic associate of I. typographus, but a multifunctional component of the bark beetle-mite-fungus system, acting simultaneously as a disperser on adult beetles, a carrier of viable entomopathogenic fungal propagules, and an opportunistic predator of susceptible beetle developmental stages. This newly documented association and regional range extension highlight the need to incorporate acarid mites into ecological and applied frameworks of bark beetle dynamics in European spruce forests.

Micropterigidae is regarded as the sister group of all the other Lepidoptera, providing important insights into the evolution of Lepidoptera. However, the gene and protein profiles of silk from Micropterigidae have not yet been identified. In this study, we investigate the components of silk cocoons of the micropterigid species Neomicropteryx cornuta. Here we show that the protein fibroin heavy chain (FibH) is absent in the silk of N. cornuta and that the putative homolog of fibroin light chain (FibL) is also absent or severely altered. This is confirmed by transcriptome and genome analyses of the conserved regions in this species. The examination of the synteny around the fibH genes in several Lepidoptera and Trichoptera species shows that the genomic region containing this gene is absent in another micropterigid species, Micropterix aruncella. In contrast, we found putative orthologs of fibH and fibL in the representative transcripts of another distinct clade, Eriocraniidae. This study shows that the loss of FibH and the loss or severe divergence of FibL occurrs specifically in the family Micropterigidae and reveals dynamic evolutionary changes in silk composition during the early evolution of Lepidoptera. It also shows that silk proteins without FibH can form a solid cocoon.

Silk materials have been extensively studied across several insect groups; however, dipterans remain largely unexplored. In this study, we examined the silk-like secretions of Keroplatus testaceus larvae using histochemistry, transcriptomics, proteomics, mechanical assays, and Fourier-transform infrared (FTIR) spectroscopy. Our results show that a single pair of labial salivary glands produces two distinct secretions, the mucus web and the cocoon, which differ in both composition and function. Neither secretion contains fibroin. Instead, both are composed of a complex mixture of hydrophilic proteins, including collagen-like, mucin-like, novel proline-rich proteins, peroxidases, protease inhibitors, and other proteins with no clear homologs in other species. Structural predictions and FTIR analysis of the cocoon reveal the presence of secondary structures, including β-sheets, α-helices, and polyproline II helices. Although the secretion lacks the characteristic fibrillar core of fibroin-based silks, it is highly hydrated, rich in proline-containing proteins, and exhibits relatively high mechanical strength. These findings confirm that K. testaceus produces a highly specialized silk-like material that is structurally and compositionally adapted to larval life within wood-decomposing fungal fruiting bodies.

The larvae of the moth Hyalophora cecropia spin silk cocoons with morphologically distinct layers. We investigated the expression of the individual silk protein components of these cocoons in relation to the morphology of the silk gland and its affiliation to the different layers of the cocoon. The study used transcriptomic and proteomic analyses to identify 91 proteins associated with the silk cocoons, 63 of which have a signal peptide indicating their secretory nature. We checked the specificity of their expression in different parts of the SG and the presence of the corresponding protein products in each cocoon layer. Differences were observed among less abundant proteins with unclear functions. The representation of proteins in the inner envelope and intermediate space was similar, except for a higher proportion of probable contaminating proteins, mostly originating from the gut. On the other hand, the outer envelope contains a number of putative enzymes with unclear function. However, the protein most specific to the outer layer has sequence homology to putative serine/threonine kinase-like proteins and some adhesive proteins, and its closest homolog in Bombyx mori was found in the scaffold silk. This research provides valuable insights into the silk production of the cecropia moth, highlighting both similarities and differences to other moth species.

Lepidopteran silk is a complex mixture of proteins, consisting mainly of fibroins and sericins. Sericins are a small family of highly divergent proteins that serve as adhesives and coatings for silk fibers. So far, five genes encoding sericin proteins have been identified in Bombyx mori. Having previously identified sericin protein 150 (SP150) as a major sericin-like protein in the cocoons of the pyralid moths Galleria mellonella and Ephestia kuehniella, we describe the identification of its homolog in B. mori. Our refined gene model shows that it consists of four exons and a long open reading frame with a conserved motif, CXCXCX, at the C-terminus, reminiscent of the structure observed in a class of mucin proteins. Notably, despite a similar expression pattern, both mRNA and protein levels of B. mori SP150 were significantly lower than those of its pyralid counterpart. We also discuss the synteny of homologous genes on corresponding chromosomes in different moth species and the possible phylogenetic relationships between SP150 and certain mucin-like proteins. Our results improve our understanding of silk structure and the evolutionary relationships between adhesion proteins in the silk of different lepidopteran species.

Caddisfly larvae produce silk containing heavy and light fibroins, similar to the silk of Lepidoptera, for the construction of underwater structures. We analyzed the silk of Limnephilus lunatus belonging to the case-forming suborder Integripalpia. We analyzed the transcriptome, mapped the transcripts to a reference genome and identified over 80 proteins using proteomic methods, and checked the specificity of their expression. For comparison, we also analyzed the transcriptome and silk proteome of Limnephilus flavicornis. Our results show that fibroins and adhesives are produced together in the middle and posterior parts of the silk glands, while the anterior part produces enzymes and an unknown protein AT24. The number of silk proteins of L. lunatus far exceeds that of the web-spinning Plectrocnemia conspersa, a previously described species from the suborder Annulipalpia. Our results support the idea of increasing the structural complexity of silk in rigid case builders compared to trap web builders.

One of the major functions of programmed cell death (apoptosis) is the removal of cells that suffered oncogenic mutations, thereby preventing cancerous transformation. By making use of a Double-Headed-EP (DEP) transposon, a P element derivative made in our laboratory, we made an insertional mutagenesis screen in Drosophila melanogaster to identify genes that, when overexpressed, suppress the p53-activated apoptosis. The DEP element has Gal4-activatable, outward-directed UAS promoters at both ends, which can be deleted separately in vivo. In the DEP insertion mutants, we used the GMR-Gal4 driver to induce transcription from both UAS promoters and tested the suppression effect on the apoptotic rough eye phenotype generated by an activated UAS-p53 transgene. By DEP insertions, 7 genes were identified, which suppressed the p53-induced apoptosis. In 4 mutants, the suppression effect resulted from single genes activated by 1 UAS promoter (Pka-R2, Rga, crol, and Spt5). In the other 3 (Orct2, Polr2M, and stg), deleting either UAS promoter eliminated the suppression effect. In qPCR experiments, we found that the genes in the vicinity of the DEP insertion also showed an elevated expression level. This suggested an additive effect of the nearby genes on suppressing apoptosis. In the eukaryotic genomes, there are coexpressed gene clusters. Three of the DEP insertion mutants are included, and 2 are in close vicinity of separate coexpressed gene clusters. This raises the possibility that the activity of some of the genes in these clusters may help the suppression of the apoptotic cell death.

The larvae of moth, Hyalophora cecropia, spin silk cocoons with morphologically distinct layers. We investigated the expression of the individual silk protein components of these cocoons in relation to the morphology of the silk gland and its affiliation to the different layers of the cocoon. The study utilized transcriptomic and proteomic analyses to identify 91 proteins associated with the silk cocoons, with 63 having a signal peptide indicating their secretory nature. We checked the specificity of their expression in different parts of the SG and the presence of the corresponding protein products in each cocoon layer. Differences were observed among less abundant proteins with unclear functions. The representation of proteins in the inner envelope and intermediate space was similar, except for a higher proportion of contaminating proteins, mostly originating from the gut. On the other hand, the outer envelope contains a number of putative enzymes with unclear function. Unlike many moths, the cecropia moth produces a relatively small amount of sericins in its silk. Additionally, sericins are produced in the frontal part of the posterior silk gland. This research provides valuable insights into the silk production of the cecropia moth, highlighting both similarities and differences compared to other moth species.

ABSTRACT The classical model of sex chromosome evolution has been recently challenged in moths and butterflies (Lepidoptera). According to the current hypothesis, the adoption of a supernumerary chromosome may have driven the transition from the Z0 to the WZ sex chromosome system in females. However, the evolutionary history of the W chromosome remains enigmatic, especially in the early-diverging lepidopteran lineages. In ghost moths of the family Hepialidae, one of the most basal lepidopteran clades, there is conflicting evidence regarding their sex chromosomes. In this study, we aimed to clarify the status of the hepialid W chromosome. Using cytogenetics and genomics, we investigated the karyotype, sex chromosomes, genome size and repeatome of multiple ghost moth species and reconstructed basic phylogenetic relationships in the group. Our data show that Hepialidae have unusually large genomes (reaching up to 1C = 3 Gb) and are the oldest known lepidopteran clade with a W chromosome. However, the W does not form a typical heterochromatin body in polyploid nuclei, known as sex chromatin, previously employed to detect the presence of W chromosomes across Lepidoptera. Moreover, in some species, the W does not exhibit distinct repeat content and can escape detection via methods that rely on W-specific sequences. Analysis of the Z chromosome confirmed highly conserved gene content, arguing for a possible origin of the hepialid W chromosome from a B chromosome. We hypothesize that the mechanism underlying the formation of sex chromatin could be used in future research to study the origin of the W chromosome.

Sericins are a small family of highly divergent proteins that serve as adhesives and coatings for silk fibers and are produced in the middle part of the silk gland. So far, five genes encoding sericin proteins have been found in Bombyx mori. Sericins 1 and 3 are responsible for silk adhesion in the cocoon, while sericins 2, 4, and 5 are present in non-cocoon spun silk of younger larvae (including the early last instar). We found a new gene, which we named P150/sericin 6, which appears to be an ortholog of the sericin-like protein previously found in Galleria mellonella. The B. mori sequence of the P150/sericin 6 ORF was previously incorrectly predicted and assigned to two smaller, uncharacterized genes. We present a new P150/sericin 6 gene model and show that it encodes a large protein of 467 kDa. It is characterized by repeats with a high proportion of threonine residues and a short conserved region with a cysteine knot motif (CXCXCX) at the C-terminus. Expression analyzes have shown that B. mori P150/ser6 has low transcriptional level in contrast to its G. mellonella homolog. We also discuss the synteny of homologous genes on corresponding chromosomes between moth species and possible phylogenetic relationships between P150/ser6 and cysteine knot mucins. Our results improve our understanding of the evolutionary relationships between adhesion proteins in different lepidopteran species.

The silk produced by Lepidoptera caterpillars is a mixture of proteins secreted by the transformed labial glands, the silk glands (SG). The silk fiber consists of insoluble filamentous proteins that form a silk core and are produced in the posterior part of the SG and soluble coat proteins consisting of sericins and various other polypeptides secreted in the middle part of the SG. We constructed a silk gland specific transcriptome of Andraca theae and created a protein database required for peptide mass fingerprinting. We identified major silk components by proteomic analysis of cocoon silk and by searching for homologies with known silk protein sequences from other species. We identified 30 proteins including a heavy chain fibroin, a light chain fibroin and fibrohexamerin (P25) that form the silk core, as well as members of several structural families that form the silk coating. To uncover the evolutionary relationships among silk proteins, we included orthologs of silk genes from several recent genome projects and performed phylogenetic analyses. Our results confirm the recent molecular classification that the family Endromidae appears to be slightly more distant from the family Bombycidae. Our study provides important information on the evolution of silk proteins in the Bombycoidea, which is needed for proper annotation of the proteins and future functional studies.

ABSTRACT Sericins are a small family of highly divergent proteins that serve as adhesives and coatings for silk fibers and are produced in the middle part of the silk gland. So far, five genes encoding sericin proteins have been found in Bombyx mori . Sericins 1 and 3 are responsible for silk adhesion in the cocoon, while sericins 2, 4, and 5 are present in non-cocoon spun silk of younger larvae (including the early last instar). We found a new gene, which we named P150/sericin 6 , which appears to be an ortholog of the sericin-like protein previously found in Galleria mellonella . The B. mori sequence of the P150/sericin 6 ORF was previously incorrectly predicted and assigned to two smaller, uncharacterized genes. We present a new P150/sericin 6 gene model and show that it encodes a large protein of 467 kDa. It is characterized by repeats with a high proportion of threonine residues and a short conserved region with a cysteine knot motif (CXCXCX) at the C-terminus. Expression analysis has shown that B. mori P150/ser6 has low transcriptional level in contrast to its G. mellonella homolog. We also discuss the synteny of homologous genes on corresponding chromosomes between moth species and possible phylogenetic relationships between P150/ser6 and cysteine knot mucins. Our results improve our understanding of the evolutionary relationships between adhesion proteins in different lepidopteran species.

Similar to Lepidoptera, the larvae of Trichoptera are also capable of producing silk. Plectrocnemia conspersa , a predatory species belonging to the suborder Annulipalpia, builds massive silken retreats with preycapturing nets. In this study, we describe the silk glands of P. conspersa and use the multi-omics methods to obtain a complete picture of the fiber composition. A combination of silk gland-specific transcriptome and proteomic analyses of the spun-out fibers yielded 27 significant candidates whose full-length sequences and gene structures were retrieved from the publicly available genome database. About one-third of the candidates were completely novel proteins for which there are no described homologs, including a group of five pseudofibroins, proteins with a composition similar to fibroin heavy chain. The rest were homologs of lepidopteran silk proteins, although some had a larger number of paralogs. On the other hand, P. conspersa fibers lacked some proteins that are regular components in moth silk. In summary, the multi-omics approach provides an opportunity to compare the overall composition of silk with other insect species. A sufficient number of such studies will make it possible to distinguish between the basic components of all silks and the proteins that represent the adaptation of the fibers for specific purposes or environments.

This dataset contains: 1) Ephestia_kuehniella_transcriptome_initial.fa: the initial de novo assembly of the silk gland-specific transcriptome of Ephestia kuehniella. 2) Ephestia_kuehniella_transcriptome_improved.fa: the improved transcriptome by incorporating long-read genomic data. For details please see: Wu BC-H, Šauman I, Maaroufi HO, Žaloudíková A, Žurovcová M, Kludkiewicz B, Hradilová M and Žurovec M (2022), Characterization of silk genes in Ephestia kuehniella and Galleria mellonella revealed duplication of sericin genes and highly divergent sequences encoding fibroin heavy chains. Front. Mol. Biosci. 9:1023381. doi: 10.3389/fmolb.2022.1023381

Many lepidopteran species produce silk, cocoons, feeding tubes, or nests for protection from predators and parasites for caterpillars and pupae. Yet, the number of lepidopteran species whose silk composition has been studied in detail is very small, because the genes encoding the major structural silk proteins tend to be large and repetitive, making their assembly and sequence analysis difficult. Here we have analyzed the silk of Yponomeuta cagnagella, which represents one of the early diverging lineages of the ditrysian Lepidoptera thus improving the coverage of the order. To obtain a comprehensive list of the Y. cagnagella silk genes, we sequenced and assembled a draft genome using Oxford Nanopore and Illumina technologies. We used a silk-gland transcriptome and a silk proteome to identify major silk components and verified the tissue specificity of expression of individual genes. A detailed annotation of the major genes and their putative products, including their complete sequences and exon-intron structures is provided. The morphology of silk glands and fibers are also shown. This study fills an important gap in our growing understanding of the structure, evolution, and function of silk genes and provides genomic resources for future studies of the chemical ecology of Yponomeuta species.

The use of parthenogenetic silkworm ( Bombyx mori ) strains, which eliminate the problem of recombination, is a useful tool for maintaining transgenic clonal lines. The generation of genetically identical individuals is becoming an important tool in genetic engineering, allowing replication of an existing advantageous trait combination without the mixing that occurs during sexual reproduction. Thus, an animal with a particular genetic modification, such as the ability to produce transgenic proteins, can reproduce more rapidly than by natural mating. One obstacle to the widespread use of parthenogenesis in silkworm genetic engineering is the relatively low efficiency of downstream transgenesis techniques. In this work, we seek to optimize the use of transgenesis in conjunction with the production of parthenogenetic individuals. We found that a very important parameter for the introduction of foreign genes into a parthenogenetic strain is the precise timing of embryo microinjection. Our modification of the original method increased the efficiency of transgene injection as well as the survival rate of injected embryos. We also provide a detailed description of the methodological procedure including a graphical overview of the entire protocol.

Concentrative nucleoside transporters (Cnts) are unidirectional carriers that mediate the energy-costly influx of nucleosides driven by the transmembrane sodium gradient. Cnts are transmembrane proteins that share a common structural organization and are found in all phyla. Although there have been studies on Cnts from a biochemical perspective, no deep research has examined their role at the organismal level. Here, we investigated the role of the Drosophila melanogaster cnt1 gene, which is specifically expressed in the testes. We used the CRISPR/Cas9 system to generate a mutation in the cnt1 gene. The cnt1 mutants exhibited defects in the duration of copulation and spermatid maturation, which significantly impaired male fertility. The most striking effect of the cnt1 mutation in spermatid maturation was an abnormal structure of the sperm tail, in which the formation of major and minor mitochondrial derivatives was disrupted. Our results demonstrate the importance of cnt1 in male fertility and suggest that the observed defects in mating behavior and spermatogenesis are due to alterations in nucleoside transport and associated metabolic pathways.

Silk is a secretory product of numerous arthropods with remarkable mechanical properties. In this work, we present the complete sequences of the putative major silk proteins of E. kuehniella and compare them with those of G. mellonella, which belongs to the same moth family Pyralidae. To identify the silk genes of both species, we combined proteomic analysis of cocoon silk with a homology search in transcriptomes and genomic sequences to complement the information on both species. We analyzed structure of the candidate genes obtained, their expression specificity and their evolutionary relationships. We demonstrate that the silks of E. kuehniella and G. mellonella differ in their hydrophobicity and that the silk of E. kuehniella is highly hygroscopic. In our experiments, we show that the number of genes encoding sericins is higher in G. mellonella than in E. kuehniella. By analyzing the synteny of the chromosomal segment encoding sericin genes in both moth species, we found that the region encoding sericins is duplicated in G. mellonella. Finally, we present the complete primary structures of nine fibH genes and proteins from both families of the suborder Pyraloidea and discuss their specific and conserved features. This study provides a foundation for future research on the evolution of silk proteins and lays the groundwork for future detailed functional studies.

Larvae of many lepidopteran species produce a mixture of secretory proteins, known as silk, for building protective shelters and cocoons. Silk consists of a water-insoluble silk filament core produced in the posterior silk gland (PSG) and a sticky hydrophilic coating produced by the middle silk gland (MSG). In Bombyx mori, the fiber core comprises three proteins: heavy chain fibroin (Fib-H), light chain fibroin (Fib-L) and fibrohexamerin (Fhx, previously referred to as P25). To learn more about the role of Fhx, we used transcription activator-like effector nuclease (TALEN) mutagenesis and prepared a homozygous line with a null mutation in the Fhx gene. Our characterization of cocoon morphology and silk quality showed that the mutation had very little effect. However, a detailed inspection of the secretory cells in the posterior silk gland (PSG) of mid-last-instar mutant larvae revealed temporary changes in the morphology of the endoplasmic reticulum. We also observed a morphological difference in fibroin secretory globules stored in the PSG lumen of Fhx mutants, which suggests that their fibroin complexes have a slightly lower solubility. Finally, we performed an LC-MS-based quantitative proteomic analysis comparing mutant and wild-type (wt) cocoon proteins and found a high abundance of a 16 kDa secretory protein likely involved in fibroin solubility. Overall, our study shows that whilst Fhx is dispensable for silk formation, it contributes to the stability of fibroin complexes during intracellular transport and affects the morphology of fibroin secretory globules in the PSG lumen.