Toxin diversity revealed by the venom gland transcriptome of Pardosa pseudoannulata, a natural enemy of several insect pests

Integrated transcriptome and metabolome analysis reveals the molecular responses of Pardosa pseudoannulata to hypoxic environments

Terrestrial organisms are likely to face hypoxic stress during natural disasters such as floods or landslides, which can lead to inevitable hypoxic conditions for those commonly residing within soil. Pardosa pseudoannulata often inhabits soil crevices and has been extensively studied, yet research on its response to hypoxic stress remains unclear. Therefore, we investigated the adaptive strategies of Pardosa pseudoannulata under hypoxic stress using metabolomics and transcriptomics approaches. The results indicated that under hypoxic stress, metabolites related to energy and antioxidants such as ATP, D-glucose 6-phosphate, flavin adenine dinucleotide (FAD), and reduced L-glutathione were significantly differentially expressed. Pathways such as the citric acid (TCA) cycle and oxidative phosphorylation were significantly enriched. Transcriptome analysis and related assessments also revealed a significant enrichment of pathways associated with energy metabolism, suggesting that Pardosa pseudoannulata primarily copes with hypoxic environments by modulating energy metabolism and antioxidant-related substances.

The complete mitogenome of the pond wolf spider Pardosa pseudoannulata, with phylogenetic implications for the Lycosidae

The pond wolf spider Pardosa pseudoannulata Bösenberg & Strand, 1906 (Araneae: Lycosidae) is an important predator of agricultural pests in southern, eastern and southeastern Asia. Here, we report the complete mitogenome of this spider reconstructed from Illumina sequencing data. The circular mitogenome length is 14,533 bp with the nucleotide composition A (33.3%), C (8.2%), G (15.2%), and T (43.3%). The P. pseudoannulata mitogenome comprises 13 protein-coding genes, 22 transfer RNA genes, two ribosomal RNA genes, and a control region. Phylogenetic analyses of Lycosidae mitogenomes supported the monophyly of the subfamily Pardosinae and the two genera Pardosa and Alopecosa, and indicated the polyphyly of the subfamily Lycosinae and the paraphyly of its type genus Lycosa. In this study, P. pseudoannulata is the closest relative to P. pusiola. These results provide useful genetic information for future studies on the diversity, phylogeny, and evolution for wolf spiders.

Single domain von Willebrand factor type C "cytokines" and the regulation of the stress/immune response in insects

The single domain von Willebrand factor type C (SVWC) appears in small secreted peptides that are arthropod-specific and are produced following environmental stress or pathogen exposure. Most research has focused on proteins with SVWC domain that are induced after virus infection and are hypothesized to function as "cytokines" to regulate the innate immune response. The expansion of SVWC genes in insect species indicates that many other functions remain to be discovered. Research in shrimp has elucidated the adaptability of Vago-like peptides in the innate immune response against bacteria, fungi and viruses after activation by Jak-STAT and/or Toll/Imd pathways in which they can act as pathogen-recognition receptors or cytokine-like signaling molecules. SVWC factors also appear in scorpion venoms and tick saliva, underlining their versatility to acquire new functions. This review discusses the discovery and function of SVWC peptides from insects to crustaceans and chelicerates and reveals the enormous gaps in knowledge that remain to be filled to understand this enigmatic group of secreted peptides.

Transcriptome-based analyses reveal venom diversity in two araneomorph spiders, Psechrus triangulus and Hippasa lycosina

The spiders Psechrus triangulus and Hippasa lycosina are widely distributed in Yunnan Province, China, and are important natural enemies of agricultural pests, yet studies regarding the composition of their venom are lacking. In this study, cDNA libraries were constructed from venom gland tissue of P. triangulus and H. lycosina and used for transcriptomic analysis. From the analysis, 39 and 31 toxin-like sequences were predicted for P. triangulus and H. lycosina, respectively. The predicted neurotoxin sequences were categorized according to cysteine sequence motifs, and the predicted neurotoxin sequences of P. triangulus and H. lycosina could be classified into 9 and 6 toxin families, respectively. In addition, potential acetylcholinesterase, hyaluronidase, and astaxanthin-like metalloproteinases were identified through annotation. In summary, transcriptomic techniques were invaluable in mining the gene expression information from these two spider species to explore the toxin composition of their venom and determine how they differ. Studies of this type provide essential baseline data for studying the evolution and physiological activities of spider toxins and for the potential development of medicinal compounds.

Structural and evolutionary insights into astacin metallopeptidases

The astacins are a family of metallopeptidases (MPs) that has been extensively described from animals. They are multidomain extracellular proteins, which have a conserved core architecture encompassing a signal peptide for secretion, a prodomain or prosegment and a zinc-dependent catalytic domain (CD). This constellation is found in the archetypal name-giving digestive enzyme astacin from the European crayfish Astacus astacus. Astacin catalytic domains span ∼200 residues and consist of two subdomains that flank an extended active-site cleft. They share several structural elements including a long zinc-binding consensus sequence (HEXXHXXGXXH) immediately followed by an EXXRXDRD motif, which features a family-specific glutamate. In addition, a downstream SIMHY-motif encompasses a "Met-turn" methionine and a zinc-binding tyrosine. The overall architecture and some structural features of astacin catalytic domains match those of other more distantly related MPs, which together constitute the metzincin clan of metallopeptidases. We further analysed the structures of PRO-, MAM, TRAF, CUB and EGF-like domains, and described their essential molecular determinants. In addition, we investigated the distribution of astacins across kingdoms and their phylogenetic origin. Through extensive sequence searches we found astacin CDs in > 25,000 sequences down the tree of life from humans beyond Metazoa, including Choanoflagellata, Filasterea and Ichtyosporea. We also found < 400 sequences scattered across non-holozoan eukaryotes including some fungi and one virus, as well as in selected taxa of archaea and bacteria that are pathogens or colonizers of animal hosts, but not in plants. Overall, we propose that astacins originate in the root of Holozoa consistent with Darwinian descent and that the latter genes might be the result of horizontal gene transfer from holozoan donors.

De Novo Transcriptome Analysis of the Venom of Latrodectus geometricus with the Discovery of an Insect-Selective Na Channel Modulator

The brown widow spider, Latrodectus geometricus, is a predator of a variety of agricultural insects and is also hazardous for humans. Its venom is a true pharmacopeia representing neurotoxic peptides targeting the ion channels and/or receptors of both vertebrates and invertebrates. The lack of transcriptomic information, however, limits our knowledge of the diversity of components present in its venom. The purpose of this study was two-fold: (1) carry out a transcriptomic analysis of the venom, and (2) investigate the bioactivity of the venom using an electrophysiological bioassay. From 32,505 assembled transcripts, 8 toxin families were classified, and the ankyrin repeats (ANK), agatoxin, centipede toxin, ctenitoxin, lycotoxin, scorpion toxin-like, and SCP families were reported in the L. geometricus venom gland. The diversity of L. geometricus venom was also uncovered by the transcriptomics approach with the presence of defensins, chitinases, translationally controlled tumor proteins (TCTPs), leucine-rich proteins, serine proteases, and other important venom components. The venom was also chromatographically purified, and the activity contained in the fractions was investigated using an electrophysiological bioassay with the use of a voltage clamp on ion channels in order to find if the neurotoxic effects of the spider venom could be linked to a particular molecular target. The findings show that U24-ctenitoxin-Pn1a involves the inhibition of the insect sodium (Na_v) channels, BgNa_v and DmNa_v. This study provides an overview of the molecular diversity of L. geometricus venom, which can be used as a reference for the venom of other spider species. The venom composition profile also increases our knowledge for the development of novel insecticides targeting voltage-gated sodium channels.

Neurotoxins in the venom gland of Calommata signata, a burrowing spider

Calommata signata, a burrowing spider, represents a special type of predation mode in spiders, and its utilization of toxins is different from that of web-weaving spiders and wandering spiders. The existing researches on spider toxins are mainly focused on the web-weaving and wandering spiders, but little attention on that of the burrowing spiders. Through transcriptome sequencing of C. signata venom gland and the remaining part as the counterpart tissue, 25 putative neurotoxin precursors were identified. These most neurotoxins were novel because their low similarities with the known sequences except for that of over 50% similarities in four neuropeptide toxins. The 25 neuropeptide toxins were divided into five families according to the constitution of cysteines for the possible disulfide bonds and the similarities of the deduced amino acid sequences. Besides neuropeptide toxins, other potential toxins in the venom gland were also analyzed. Unlike web-weaving spiders and wandering spiders, only a few neurotoxin genes were significantly expressed in the venom gland of C. signata. In the non-peptide toxin genes, only CsTryp_SPc-1, CsPA2-1, CsVa5-2 and four PDI genes were abundantly expressed in the venom gland. The present study provided an improved understanding on the spider toxin diversity and useful information for the exploitation of spider toxins.

Cadmium exposure alters expression of protective enzymes and protein processing genes in venom glands of the wolf spider Pardosa pseudoannulata

Cadmium (Cd) pollution is currently the most serious type of heavy metal pollution throughout the world. Previous studies have shown that Cd elevates the mortality of paddy field spiders, but the lethal mechanism remains to be explored profoundly. In the present study, we measured the activities of protective enzymes (acetylcholinesterase, glutathione peroxidase, phenol oxidase) and a heavy metal chelating protein (metallothionein) in the pond wolf spider Pardosa pseudoannulata after Cd exposure. The results indicated that Cd initially increased the enzyme activities and protein concentration of the spider after 10- and 20-day exposure before inhibiting them at 30-day exposure. Further analysis showed that the enzyme activities in the cephalothorax were inhibited to some extent. Since the cephalothorax region contains important venom glands, we performed transcriptome sequencing (RNA-seq) analysis of the venom glands collected from the spiders after long-term Cd exposure. RNA-seq yielded a total of 2826 differentially expressed genes (DEGs), and most of the DEGs were annotated into the process of protein synthesis, processing and degradation. Furthermore, a mass of genes involved in protein recognition and endoplasmic reticulum (ER) -associated protein degradation were down-regulated. The reduction of protease activities supports the view that protein synthesis and degradation in organelles and cytoplasm were dramatically inhibited. Collectively, our outcomes illustrate that Cd poses adverse effects on the expression of protective enzymes and protein, which potentially down-regulates the immune function in the venom glands of the spiders via the alteration of protein processing and degradation in the ER.

Proteotranscriptomic Insights into the Venom Composition of the Wolf Spider Lycosa tarantula

Spider venoms represent an original source of novel compounds with therapeutic and agrochemical potential. Whereas most of the research efforts have focused on large mygalomorph spiders, araneomorph spiders are equally promising but require more sensitive and sophisticated approaches given their limited size and reduced venom yield. Belonging to the latter group, the genus Lycosa ("wolf spiders") contains many species widely distributed throughout the world. These spiders are ambush predators that do not build webs but instead rely strongly on their venom for prey capture. Lycosa tarantula is one of the largest species of wolf spider, but its venom composition is unknown. Using a combination of RNA sequencing of the venom glands and venom proteomics, we provide the first overview of the peptides and proteins produced by this iconic Mediterranean spider. Beside the typical small disulfide rich neurotoxins, several families of proteins were also identified, including cysteine-rich secretory proteins (CRISP) and Hyaluronidases. Proteomic analysis of the electrically stimulated venom validated 30 of these transcriptomic sequences, including nine putative neurotoxins and eight venom proteins. Interestingly, LC-MS venom profiles of manual versus electric stimulation, as well as female versus male, showed some marked differences in mass distribution. Finally, we also present some preliminary data on the biological activity of L. tarantula crude venom.

Spider Venom: Components, Modes of Action, and Novel Strategies in Transcriptomic and Proteomic Analyses

This review gives an overview on the development of research on spider venoms with a focus on structure and function of venom components and techniques of analysis. Major venom component groups are small molecular mass compounds, antimicrobial (also called cytolytic, or cationic) peptides (only in some spider families), cysteine-rich (neurotoxic) peptides, and enzymes and proteins. Cysteine-rich peptides are reviewed with respect to various structural motifs, their targets (ion channels, membrane receptors), nomenclature, and molecular binding. We further describe the latest findings concerning the maturation of antimicrobial, and cysteine-rich peptides that are in most known cases expressed as propeptide-containing precursors. Today, venom research, increasingly employs transcriptomic and mass spectrometric techniques. Pros and cons of venom gland transcriptome analysis with Sanger, 454, and Illumina sequencing are discussed and an overview on so far published transcriptome studies is given. In this respect, we also discuss the only recently described cross contamination arising from multiplexing in Illumina sequencing and its possible impacts on venom studies. High throughput mass spectrometric analysis of venom proteomes (bottom-up, top-down) are reviewed.