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The enzyme glutamate-cysteine ligase catalytic subunit (Gclc) is a rate-limiting enzyme in the biosynthesis of glutathione that is involved in antioxidant defense, detoxification of xenobiotics, and/or its metabolites and regulates the cell cycle and immune function. Therefore, Gclc presents an appealing target for the development of novel insecticides. In this study, we conducted high-throughput virtual screening from the ZINC20 database and identified three compounds with high binding affinity to the Tribolium castaneum Gclc (TcGclc). Ultimately, we selected ZINC000032992384 due to its superior stability and lowest binding energy, as determined through molecular dynamics simulations. Bioassay results revealed that the IC 50 value of ZINC000032992384 was 19.70 μM lower than that of BSO (49.67 μM). Furthermore, the larval mortality in the ZINC000032992384 treated group was 63.8%, significantly higher than that of the controls (29.1% in the dichlorvos group and 6.4% in the acetone group). This study provides novel insights for the development of a Gclc-targeted inhibitor as a potent insecticide based on the interaction between receptors and ligands.

Depending on the respective research question, LC-MS/MS based bottom-up proteomics poses challenges from the initial biological sample all the way to data evaluation. The focus of this study was to investigate the influence of sample preparation techniques and data analysis parameters on protein identification in Tribolium castaneum by applying free software proteomics platform Max Quant. Multidimensional protein extraction strategies in combination with electrophoretic or chromatographic off-line protein pre-fractionation were applied to enhance the spectrum of isolated proteins from T. castaneum and reduce the effect of co-elution and ion suppression effects during nano-LC-MS/MS measurements of peptides. For comprehensive data analysis, MaxQuant was used for protein identification and R for data evaluation. A wide range of parameters were evaluated to gain reproducible, reliable, and significant protein identifications. A simple phosphate buffer, pH 8, containing protease and phosphatase inhibitor cocktail and application of gentle extraction conditions were used as a first extraction step for T.castaneum proteins. Furthermore, a two-dimensional extraction procedure in combination with electrophoretic pre-fractionation of extracted proteins and subsequent in-gel digest resulted in almost 100% increase of identified proteins when compared to chromatographic fractionation as well as one-pot-analysis. The additionally identified proteins could be assigned to new molecular functions or cell compartments, emphasizing the positive effect of extended sample preparation in bottom-up proteomics. Besides the number of peptides during post-processing, MaxQuant's Match between Runs exhibited a crucial effect on the number of identified proteins. A maximum relative standard deviation of 2% must be considered for the data analysis. Our work with Tribolium castaneum larvae demonstrates that sometimes - depending on matrix and research question - more complex and time-consuming sample preparation can be advantageous for isolation and identification of additional proteins in bottom-up proteomics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Background: Tribolium castaneum (Herbst) is one of the most important secondary storage pests of all types of flour and flour-based products. The present study focuses on the fragment producing behaviour of T. castaneum in wheat flour during storage and its effect on the quality parameters and defect action level (DAL) of fragments. The US Food and Drug Administration has set a DAL of 75 insect fragments in 50 g of flour. Box-Behnken design was used to optimize the storage conditions (storage period in days and temperature in degrees Celsius) and insect density (numbers) to keep insect fragments below the DAL., Results: Optimization results indicated that the presence of single number of adult of T. castaneum is enough to cross the DAL of insect fragments within a storage period of 21 days at a storage temperature of 30 °C. Insect fragments cause perceptible changes in the quality of wheat flour. When sample attained DAL of T. castaneum fragments in wheat flour,the various quality parameters were analysed in that moisture content of wheat flour was 10.8 ± 0.26%, total colour change was 2.052 (ΔE value), T. castaneum progeny emergence was 19.66 ± 1, uric acid was 1.8 ± 0.16 g kg -1 and microbial count was 7.34 ± 0.5 cfu g -1 ., Conclusions: Results from the present study indicate that the presence of even a single adult of stored pest in wheat flour should not be ignored. It is mandatory to determine the threshold level and frequent sampling is required to achieve zero tolerance of stored product insects in food commodities. © 2021 Society of Chemical Industry., (© 2021 Society of Chemical Industry.)

Successful host search by parasitic wasps is often mediated by host-associated chemical cues. The ectoparasitoid Holepyris sylvanidis is known to follow chemical trails released by host larvae of the confused flour beetle, Tribolium confusum, for short-range host location. Although the hexane-extractable trails consist of stable, long-chain cuticular hydrocarbons (CHCs) with low volatility, the kairomonal activity of a trail is lost two days after release. Here, we studied whether this loss of kairomonal activity is due to changes in the chemical trail composition induced by microbial activity. We chemically analyzed trails consisting of hexane extracts of T. confusum larvae after different time intervals past deposition under sterile and non-sterile conditions. GC-MS analyses revealed that the qualitative and quantitative pattern of the long-chain CHCs of larval trails did not significantly change over time, neither under non-sterile nor sterile conditions. Hence, our results show that the loss of kairomonal activity of host trails is not due to microbially induced changes of the CHC pattern of a trail. Interestingly, the kairomonal activity of trails consisting of host larval CHC extracts was recoverable after two days by applying hexane to them. After hexane evaporation, the parasitoids followed the reactivated host trails as they followed freshly laid ones. Cryo-scanning electron microscopy showed that the trails gradually formed filament-shaped microstructures within two days. This self-assemblage of CHCs was reversible by hexane application. Our study suggests that the long-chain CHCs of a host trail slowly undergo solidification by a self-assembling process, which reduces the accessibility of CHCs to the parasitoid's receptors as such that the trail is no longer eliciting trail-following behavior., (© 2021. The Author(s).)

Phosphine resistance is a worldwide issue threatening the grain industry. The cuticles of insects are covered with a layer of lipids, which protect insect bodies from the harmful effects of pesticides. The main components of the cuticular lipids are hydrocarbon compounds. In this research, phosphine-resistant and -susceptible strains of two main stored-grain insects, T. castaneum and R. dominica , were tested to determine the possible role of their cuticular hydrocarbons in phosphine resistance. Direct immersion solid-phase microextraction followed by gas chromatography-mass spectrometry (GC-MS) was applied to extract and analyze the cuticular hydrocarbons. The results showed significant differences between the resistant and susceptible strains regarding the cuticular hydrocarbons that were investigated. The resistant insects of both species contained higher amounts than the susceptible insects for the majority of the hydrocarbons, sixteen from cuticular extraction and nineteen from the homogenized body extraction for T. castaneum and eighteen from cuticular extraction and twenty-one from the homogenized body extraction for R. dominica . 3-methylnonacosane and 2-methylheptacosane had the highest significant difference between the susceptible and resistant strains of T. castaneum from the cuticle and the homogenized body, respectively. Unknown5 from the cuticle and 3-methylhentriacontane from the homogenized body recorded the highest significant differences in R. dominica . The higher hydrocarbon content is a key factor in eliminating phosphine from entering resistant insect bodies, acting as a barrier between insects and the surrounding phosphine environment., Competing Interests: The authors declare no conflict of interest.

Streptococcus pneumoniae ( S. pneumoniae ) is the most common bacterial cause of community-acquired pneumonia. Increasing rates of antibiotic-resistant S. pneumoniae strains impair therapy and necessitate alternative treatment options. In this study, we analysed insect-derived antimicrobial peptides (AMPs) for antibacterial effects on S. pneumoniae in a human in vitro infection model.AMP effects on bacterial growth were examined by colony forming unit (CFU)-assays, and growth curve measurements. Furthermore, cytotoxicity to primary human macrophages was detected by measuring lactate-dehydrogenase release to the supernatant. One AMP (Defensin 1) was tested in a model of primary human monocyte-derived macrophages infected with S. pneumoniae strain D39 and a multi-resistant clinical isolate. Inflammatory reactions were characterised by qPCR and multiplex-ELISA.In total, the antibacterial effects of 23 AMPs were characterized. Only Tribolium castaneum Defensin 1 showed significant antibacterial effects against S. pneumoniae strain D39 and a multi-resistant clinical isolate. During in vitro infection of primary human macrophages with S. pneumoniae D39, Defensin 1 displayed strong antibacterial effects, and consequently reduced bacteria-induced cytokine expression and release.In summary, Tribolium castaneum Defensin 1 showed profound antibacterial effectivity against Streptococcus pneumoniae D39 and a multi-resistant clinical isolate without unwanted cytotoxic or inflammatory side effects on human blood-derived macrophages.

Animals are exposed in nature to a variety of stressors. While stress is generally harmful, mild stress can also be beneficial and contribute to reproduction and survival. We studied the effect of five cold shock events versus a single cold shock and a control group, representing three levels of stress (harsh, mild, and no stress), on behavioral, physiological, and life-history traits of the red flour beetle (Tribolium castaneum, Herbst 1797). Beetles exposed to harsh cold stress were less active than a control group: they moved less and failed more frequently to detect a food patch. Their probability to mate was also lower. Beetle pairs exposed to harsh cold stress frequently failed to reproduce at all, and if reproducing, females laid fewer eggs, which were, as larvae in mid-development, smaller than those in the control group. However, harsh cold stress led to improved female starvation tolerance, probably due to enhanced lipid accumulation. Harsh cold shock also improved tolerance to an additional cold shock compared to the control. Finally, a single cold shock event negatively affected fewer measured response variables than the harsh cold stress, but also enhanced neither starvation tolerance nor tolerance to an additional cold shock. The consequences of a harsher cold stress are thus not solely detrimental but might even enhance survival under stressful conditions. Under benign conditions, nevertheless, harsh stress impedes beetle performance. The harsh stress probably shifted the balance point of the survival-reproduction trade-off, a shift that did not take place following exposure to mild stress., (© 2017 Institute of Zoology, Chinese Academy of Sciences.)

Anticancer peptides (ACPs) are biologically anticancer active molecules that are produced by mammals, plants, insects and microorganisms. Here, a new peptide (TC22) with the amino acid sequence MTVVLLLIVLPLLGGVHSSGIL was identified and characterized from the beetle Tribolium castaneum. We found it inhibited the growth and viability of HeLa and MCF-7 cells. Flow cytometry analysis demonstrated the TC22 induced HeLa cell apoptosis, and activated caspase-9 and caspase-3. Furthermore, TC22 led to ROS generation, and triggered p53 transcription and expression. Taken together, our results indicated that TC22 exhibited high anticancer capacity via activating p53, inducing ROS generation and through a mitochondrial pathway. This research provided a novel natural source peptide with strong anticancer capacity. These findings provide some novel insights on the potential candidate reagent in cancer treatment.

Mannitol, one of the sugar alcohols, is often used as a low-calorific carbohydrate by animals. In some insects, mannitol acts as a cryoprotectant to endure coldness, but also become a poisonous agent. Adults of the red flour beetle Tribolium castaneum were shown to recognize mannitol as a factor stimulating their feeding behavior, but it remains unclear whether T. castaneum can utilize mannitol as a source of nutrition, because the enzymes needed to metabolize mannitol are unknown in this species. This study shows that T. castaneum utilizes mannitol as a nutrient in a dietary assay based on a sole carbon source added to artificial gypsum diet. The amount of mannitol excreted was less than that ingested, suggesting that it is absorbed in the insect body. The hemolymph of T. castaneum contained no mannitol but contained trehalose, a known blood sugar in insects, even after being fed mannitol. This study also revealed that dietary mannitol was metabolized to triglyceride, the main component of the fat body, forming lipid droplets. It was found that metabolites of a mannitol-supplemented diet extend the lifespan of T. castaneum, compared with those obtained by metabolizing a mannitol-free diet. Given that the insects presented transcriptional changes upon being fed carbohydrates, it might be possible to identify specific genes related to mannitol-specific metabolism by their upregulation upon mannitol intake in T. castaneum. The present study investigated mannitol-responsive gene expression using RNA-Seq. Twenty-eight genes, including those encoding trehalose-6-phosphate synthase and fatty acid synthase, were differentially expressed between beetles that were fed or not fed mannitol. The identification of upregulated genes provides us with important insights into the molecular events following mannitol intake., Competing Interests: I have declared that no competing interests exist.

Parasitic wasps which attack insects infesting processed stored food need to locate their hosts hidden inside these products. Their host search is well-known to be guided by host kairomones, perceived via olfaction or contact. Among contact kairomones, host cuticular hydrocarbons (CHCs) may provide reliable information for a parasitoid. However, the chemistry of CHC profiles of hosts living in processed stored food products is largely unknown. Here we showed that the ectoparasitoid Holepyris sylvanidis uses CHCs of its host Tribolium confusum, a worldwide stored product pest, as kairomones for host location and recognition at short range. Chemical analysis of T. confusum larval extracts by gas chromatography coupled with mass spectrometry revealed a rich blend of long-chain (C25-C30) hydrocarbons, including n-alkanes, mono-, and dimethylalkanes. We further studied whether host larvae leave sufficient CHCs on a substrate where they walk along, thus allowing parasitoids to perceive a CHC trail and follow it to their host larvae. We detected 18 CHCs on a substrate that had been exposed to host larvae. These compounds were also found in crude extracts of host larvae and made up about a fifth of the CHC amount extracted. Behavioral assays showed that trails of host CHCs were followed by the parasitoids and reduced their searching time until successful host recognition. Host CHC trails deposited on different substrates were persistent for about a day. Hence, the parasitoid H. sylvanidis exploits CHCs of T. confusum larvae for host finding by following host CHC trails and for host recognition by direct contact with host larvae.

Telomeres are nucleoprotein complexes that maintain the ends of our chromosomes thus providing genomic stability. Telomerase is a ribonucleoprotein reverse transcriptase that replicates the short tandem repeats of DNA known as telomeres. The telomeric DNA is specifically associated with two major complexes, the shelterin and CST complexes both of which are involved in telomere length regulation and maintenance along with telomerase. Obtaining structural information on these nucleoprotein complexes has been a major bottleneck in fully understanding the mechanism of action of telomeric nucleoproteins for over two decades. The recent advances in molecular and structural biology have enabled us to obtain atomic resolution structures of telomeric proteins alone and in complex with their nucleic acid substrates transforming the field and our understanding and interpretation of this unique biological pathway. Here we report our approach to obtain the structure of the Triobolium castaneum catalytic subunit of telomerase TERT (tcTERT) in its apo- and substrate-bound states., (© 2016 Elsevier Inc. All rights reserved.)

The present experiment was designed to demonstrate differences in the degree of fodder contamination with benzoquinones at various Tribolium confusum levels, the impact of infested feed on the beetle population and the impact of infested feed on the health status of rats. The feeding studies were done on female rats divided into 3 groups: a control group and two experimental groups. Experimental groups were fed with a fodder infested by 150 individuals of T. confusum per kg (group D1) and 300 individuals of T. confusum per kg (group D2). The insects were grown in the fodder for 5 months and the contaminated fodder was given to the laboratory animals for 8 weeks. After that period the rats were sacrificed, blood was drawn for morphological, biochemical and immunological analyses, as well as the samples of internal organs were taken for histopathology. Regardless of initial degree of infestation, after 5 months incubation period the content of benzoquinones in fodder reached the maximum level that reduced beetle population. The resulting concentration to benzoquinones had no effect upon feed intake nor growth of rate, whereas caused the presence of these substances in feces, urine and also in tissues which was indicated by pathological lesions observed in the study. The results obtained point to the possibility of the benzoquinones accumulation in the organisms of farm animals fed fodder containing pests.

We studied how copper toxicity in the red flour beetle, Tribolium castaneum changed as a result of infection by the entomopathogenic nematode Steinernema feltiae. Measured traits were: respiration, growth and survival, as well as the concentrations of copper within beetle tissues and in its diet. By comparing F1 and F5 generation we were able to answer how long-term metal exposure changed the responses to both copper and the parasite. The beetles did accumulate copper; however, the results indicated that copper concentrations in beetle tissues were affected by nematode infection, the sex of the experimental animals, and the number of generations of exposure. Five generations of exposure to copper resulted in the highest dry body mass of infected beetles of both sexes; additionally, this group also had the lowest copper concentrations in their tissues. The only factor that had a significant effect on respiration was infection by nematodes: infected beetles of both sexes in both generational groups had significantly decreased respiration rates. Survival was lowest in nematode-infected animals of both sexes from both generations, regardless of exposure to copper. Our results confirm that an organism's response to metal pollution is dependent on its health status and sex. We also found that the history of exposure to metal was equally important-we found enhanced resistance to copper intoxication after only five generations of exposure.

Following a reverse pharmacology approach, we identified an allatotropin-like peptide receptor in Tribolium castaneum. Allatotropins are multifunctional neuropeptides initially isolated from the tabacco hornworm, Manduca sexta. They have been shown to be myoactive, to be cardio-acceleratory, to inhibit active ion transport, to stimulate juvenile hormone production and release and to be involved in the photic entrainment of the circadian clock. A tissue distribution analysis of the T. castaneum allatotropin-like peptide receptor by means of qRT-PCR revealed a prominent sexual dimorphism, the transcript levels being significantly higher in the male fat body and reproductive system. The endogenous ligand of the receptor, Trica-ATL, is able to increase the frequency and tonus of contractions in the gut and in the reproductive tract of mature red flour beetles., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

We report that the abdominal epidermis and associated tissues are the predominant sources of male-produced pheromones in the red flour beetle, Tribolium castaneum and, for the first time, describe the stereoisomeric composition of the natural blend of isomers of the aggregation pheromone 4,8-dimethyldecanal (DMD) in this important pest species. Quantitative analyses via gas chromatography-mass spectrometry showed that the average amount of DMD released daily by single feeding males of T. castaneum was 878 ± 72 ng (SE). Analysis of different body parts identified the abdominal epidermis as the major source of aggregation pheromone; the thorax was a minor source, while no DMD was detectable in the head. No internal organs or obvious male-specific glands were associated with pheromone deposition. Complete separation of all four stereoisomers of DMD was achieved following oxidation to the corresponding acid, derivatization with (1R, 2R)- and (1S, 2S)-2-(anthracene-2,3-dicarboximido)cyclohexanol to diastereomeric esters, and their separation on reversed-phase high-performance liquid chromatography at -54°C. Analysis of the hexane eluate from Porapak-Q-collected volatiles from feeding males revealed the presence of all four isomers (4R,8R)/(4R,8S)/(4S,8R)/(4S,8S) at a ratio of approximately 4:4:1:1. A walking orientation bioassay in a wind tunnel with various blends of the four synthetic isomers further indicated that the attractive potency of the reconstituted natural blend of 4:4:1:1 was equivalent to that of the natural pheromone and greater than that of the 1:1 blend of (4R,8R)/(4R,8S) used in commercial lures.

In several insect species, seminal fluid proteins (SFPs) have been demonstrated to be key regulators of male and female fitness through their ability to alter female physiology and behaviour. Tribolium castaneum is an economically important pest species and a model system for sexual selection research, but little is known about SFPs in this insect. To create a foundation for the study of T. castaneum SFPs, we used mass spectrometry to identify putative SFPs by comparing proteins detected in the male reproductive glands with those found in the reproductive tracts of virgin and mated females. Fourteen putative SFPs, thirteen with male biased expression, were identified through this approach. We also used reverse transcription PCR (RT-PCR) to examine expression levels across different tissue types. We found strongly male-biased expression in 13 genes, nine of which were expressed only in male accessory gland tissue. This represents the first proteomic-based method of identifying putative SFPs in any coleopteran species, and is the first study in this species to identify putative SFPs that are likely transferred to the female. This work could lead to functional analyses of the role of SFPs in sexual selection, sexual conflict and potential control of a pest species., (© 2011 The Authors. Insect Molecular Biology © 2011 The Royal Entomological Society.)

The screening of several Chinese mangrove plants for insecticidal principles showed that ethanol extract of Ceriops tagal stems and twigs possessed significant feeding deterrent activity against the red flour beetle, Tribolium castaneum (Family: Rhizophoraceae). From the ethanol extract, three feeding deterrent diterpenoids were isolated by bioassay-guided fractionation. The compounds were identified as tagalsin A, B, and H on the basis of their phytochemical and spectral data. Tagalsin A, B, and H exhibited strong feeding deterrent activity against T. castaneum adults with EC₅₀ values of 375.3 ppm, 277.3 ppm, and 285.45 ppm, respectively.

The cuticular hydrocarbons of insects are species-specific and often function as semiochemicals. The activity of Tribolium brevicornis cuticular hydrocarbons as feeding deterrents that ostensibly function to prevent pupal cannibalism and predation was evaluated. The cuticular hydrocarbons of T. brevicornis pupae were characterized and flour disk bioassays conducted with individual and combined extract components incorporated into artificial diets on which Tribolium adults fed for six days. Feeding by T. brevicornis and T. castaneum on flour disks containing cuticular extracts of T. brevicornis pupae resulted in reduced consumption and weight loss relative to feeding on control flour disks. In both cases, feeding deterrence indices exceeded 80% suggesting that T. brevicornis cuticular hydrocarbons could function to deter cannibalism and predation of pupae by larvae and adult beetles. Sixteen different cuticular hydrocarbons were identified in T. brevicornis pupal extracts. Eight of the commercially available linear alkanes were tested individually in feeding trials with eight Tribolium species. One compound (C28) significantly reduced the amount of food consumed by three species compared to control disks, whereas the compounds C25, C26, and C27 elicited increased feeding in some species. Four other compounds had no effect on consumption for any species. When four hydrocarbon mixtures were tested for synergistic deterrence on T. brevicornis and T. castaneum, none significantly influenced consumption. Our results indicate that the cuticular chemistry of T. brevicornis pupae could serve to deter predation by conspecific and congeneric beetles.

Cuticle tanning in insects involves simultaneous cuticular pigmentation and hardening or sclerotization. The dynamic mechanical properties of the highly modified and cuticle-rich forewings (elytra) from Tribolium castaneum (red flour beetle) wild-type and body color mutant strains were investigated to relate body coloration and elytral mechanical properties. There was no statistically significant variation in the storage modulus E' among the elytra from jet, cola, sooty and black mutants or between the mutants and the wild-type GA-1 strain: E' averaged 5.1 ± 0.6 GPa regardless of body color. E' is a power law function of oscillation frequency for all types. The power law exponent, n, averaged 0.032 ± 0.001 for elytra from all genotypes except black; this small value indicated that the elytra are cross-linked. Black elytra, however, displayed a significantly larger n of 0.047 ± 0.004 and an increased loss tangent (tan δ), suggesting that metabolic differences in the black mutant strain result in elytra that are less cross-linked and more pigmented than the other types. These results are consistent with the hypothesis that black elytra have a β-alanine-deficient and dopamine-abundant metabolism, leading to greater melanin (black pigment) production, probably at the expense of cross-linking of cuticular proteins mediated by N-β-alanyldopamine quinone., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Tribolium castaneum is an important agricultural pest and an advanced genetic model for coleopteran insects. We have taken advantage of the recently acquired T. castaneum genome to identify T. castaneum genes and proteins in one of the more critical environmental interfaces of the insect, the larval alimentary tract. Genetic transcripts isolated from the T. castaneum larval gut were labeled and hybridized to a custom array containing oligonucleotides from predicted genes in the T. castaneum genome. Through a ranking procedure based on relative labeling intensity, we found that approximately 17.6% of the genes represented in the array were predicted to be highly expressed in gut tissue. Several genes were selected to compare relative expression levels in larval gut, head, or carcass tissues using quantitative real-time PCR, and expression levels were, with few exceptions, consistent with the gut rankings. In parallel with the microarrays, proteins extracted from the T. castaneum larval gut were subjected to proteomic analysis. Two-dimensional electrophoretic analysis combined with MALDI-TOF resulted in the identification of 37 of 88 selected protein samples. As an alternative strategy, one-dimensional electrophoretic separation of T. castaneum larval gut proteins followed by two-dimensional nano-HPLC and ESI-MS/MS resulted in the identification of 98 proteins. A comparison of the proteomic studies indicated that 16 proteins were commonly identified in both, whereas 80 proteins from the proteomic analyses corresponded to genes with gut rankings indicative of high expression in the microarray analysis. These data serve as a resource of T. castaneum transcripts and proteins in the larval gut and provide the basis for comparative transcriptomic and proteomic studies related to the gut of coleopteran insects.

The insect arginine vasopressin-like (AVPL) peptide is of special interest because of its potential function in the regulation of diuresis. Genome sequences of the red flour beetle Tribolium castaneum yielded the genes encoding AVPL and AVPL receptor, whereas the homologous sequences are absent in the genomes of the fruitfly, malaria mosquito, silkworm, and honeybee, although a recent genome sequence of the jewel wasp revealed an AVPL sequence. The Tribolium receptor for the AVPL, the first such receptor identified in any insect, was expressed in a reporter system, and showed a strong response (EC(50)=1.5 nM) to AVPL F1, the monomeric form having an intramolecular disulfide bond. In addition to identifying the AVPL receptor, we have demonstrated that it has in vivo diuretic activity, but that it has no direct effect on Malpighian tubules. However, when the central nervous system plus corpora cardiaca and corpora allata are incubated along with the peptide and Malpighian tubules, the latter are stimulated by the AVPL peptide, suggesting it acts indirectly. Summing up all the results from this study, we conclude that AVPL functions as a monomer in Tribolium, indirectly stimulating the Malpighian tubules through the central nervous system including the endocrine organs corpora cardiaca and corpora allata. RNA interference in the late larval stages successfully suppressed mRNA levels of avpl and avpl receptor, but with no mortality or abnormal phenotype, implying that the AVPL signaling pathway may have been near-dispensable in the early lineage of holometabolous insects.

Insect chitinase (CHT) family proteins are encoded by as many as 16 genes depending upon the species of interest. We have classified these proteins in three species into five different groups based on amino acid sequence similarities (Zhu et al., companion paper). The functions of most of the individual proteins of this family during growth and development are largely unknown. To help determine their enzymatic properties and physiological roles, we expressed representative members belonging to this protein family from Drosophila melanogaster (Dm) and Tribolium castaneum (Tc), and characterized their kinetic and carbohydrate-binding properties. Seven proteins, including DmCHT 4, 5, 9 and DmDS47 from Drosophila, and TcCHT5, TcIDGF2 and TcIDGF4 from Tribolium, belonging to groups I, IV or V of the chitinase-like family were expressed in a baculovirus-insect cell line expression system, purified and characterized. Their enzymatic and chitin-binding properties were compared to those of the well-characterized chitinase, MsCHT535, from Manduca sexta (Ms). All of these proteins, except those belonging to group V that are related to imaginal disc growth factors (IDGFs), exhibited chitinolytic activity against the long polymeric substrate, CM-Chitin-RBV, and/or the short oligomeric substrate, MU-(GlcNAc)(3). TcCHT5, DmCHT5 and MsCHT535, which are members of group I chitinases, cleaved both polymeric and oligomeric substrates. Their enzymatic properties, including pH optima, kinetic parameters, and susceptibility to substrate inhibition by chitooligosaccharides, were similar. Two group IV chitinases, DmCHT4 and DmCHT9, also were characterized. DmCHT4 had one optimum pH of 6 towards the polymeric substrate and no detectable chitinolytic activity towards an oligosaccharide substrate. DmCHT9 had high activity from pH 4 to 8 towards the polymeric substrate and exhibited low activity towards the oligosaccharide substrate. The group V proteins, TcIDGF2 and TcIDGF4, contain all of the catalytically critical residues within conserved region II of family 18 chitinases but neither exhibited chitinolytic activity. Another group V protein, DmDS47, which lacks the critical glutamate residue in region II and the C-terminal CBD, also exhibited no chitinolytic activity. However, all three of the group V proteins bound to chitin tightly. A comparison of the amino acid sequences and homology model structures of group V proteins with enzymatically active members of the chitinase family indicated that the presence of additional loops of amino acids within the (betaalpha)(8)-barrel structure of these proteins interferes with productive substrate binding and/or catalysis.

More than 20 years ago, an oxytocin/vasopressin-like peptide, CLITNCPRGamide, was isolated from the locust, Locusta migratoria [Proux JP, et al. (1987) Identification of an arginine vasopressin-like diuretic hormone from Locusta migratoria. Biochem Biophys Res Commun 149:180-186]. However, no similar peptide could be identified in other insects, nor could its prohormone be cloned, or its physiological actions be established. Here, we report that the recently sequenced genome from the red flour beetle Tribolium castaneum contains a gene coding for an oxytocin/vasopressin-like peptide, identical to the locust peptide, which we named inotocin (for insect oxytocin/vasopressin-like peptide) and a gene coding for an inotocin G protein-coupled receptor (GPCR). We cloned the Tribolium inotocin preprohormone and the inotocin GPCR and expressed the GPCR in CHO cells. This GPCR is strongly activated by low concentrations of inotocin (EC(50), 5 x 10(-9) M), demonstrating that it is the inotocin receptor. Quantitative RT-PCR (qPCR) showed that in adult Tribolium, the receptor is mainly expressed in the head and much less in the hindgut and Malpighian tubules, suggesting that the inotocin/receptor couple does not play a role in water homeostasis. Surprisingly, qPCR also showed that the receptor is 30x more expressed in the first larval stages than in adult animals. The inotocin/receptor couple can also be found in the recently sequenced genome from the parasitic wasp Nasonia vitripennis but not in any other holometabolous insect with a completely sequenced genome (12 Drosophila species, the malaria mosquito Anopheles gambiae, the yellow fever mosquito Aedes aegypti, the silk worm Bombyx mori, and the honey bee Apis mellifera), suggesting that this neuropeptide system is confined to basal holometabolous insects. Furthermore, we identified an oxytocin/vasopressin-like peptide and receptor in the recently sequenced genome from the water flea Daphnia pulex (Crustacea). To our knowledge, this is the first report on the molecular cloning of an oxytocin/vasopressin-like receptor and its ligand from arthropods.

Four neuropeptides were identified from the brain and corpora cardiaca-corpora allata (CC-CA) of the mealworm beetle Tenebrio molitor using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and information derived from the genome of the red flour beetle, Tribolium castaneum. Leucomyosuppressin (a FLRFamide), previously associated with cockroaches, but also subsequently identified from honey bee seen as a prominent peptide in both brain and CC-CA of T.molitor. A coding sequence for this peptide is found in the genome of T. castaneum. In addition, three FXPRLamides (pyrokinins), provisionally Tenmo-PK-1, Tenmo-PK-2 and Tenmo-PK-3 (HVVNFTPRLamide, SPPFAPRLamide, HL(I)SPFSPRLamide) were identified in both CC-CA and brain of T. molitor, again on the basis of predicted occurrence or similarity in T. castaneum. The sequence of Tenmo-PK-2 is the same as the PK-2 of the cockroach, Periplaneta americana. Other peptides readily predicted from the genome of T. castaneum include two AKH/HrTH peptides (Trica-AKH-1; pELNFSTDWamide and Trica-AKH-2; pELNFTPNWamide), the second of which is identical to Pyrap-AKH, an AKH-related peptide (Trica AKH-L; pEVTFSRDWPamide), two CRF-related diuretic factors (Trica-DH 37 and Trica-DH 47), the latter identical to Tenmo-DH 47, a putative antidiuretic factor (Trica-ADFb; LYDDGSYKPHVYGF-OH), two sulfakinin-like peptides (Trica-SK-1; pETSDDY(SO(3))GHLRFamide, and Trica SK-2; GEEPFDDYGHMRFamide), a potential allatostatin-C (Trica-AS; pESRYRQCYFNPISCF-OH), six allatostatin-B/myoinhibitory peptides (Trica-AST-B-1,2,3,4,5 & 6; DWNKDLHIWamide, GWNNLHEGWamide, AWQSLQSGWamide, NWGQFHGGWamide, SKWDNFRGSWamide, EPAWSNLGIWamide), an allatotropin-like peptide (Trica-ATL; GIEALKYHNMDLGTARGYamide), four 'CAPA'-related peptides (Trica-CAPA-1,2,3,4; NKLASVYALTPSLRVamide, RIGKMVSFPRIamide, PGANSGGMWFGPRLamide, SENFTPWAYIILNGEAPIIREVHYSPRLamide), proctolin (RYLPT), a potential SIFamide (Trica-SIFa; TYRKPPFNGSIFamide), an arginine-vasopressin-related peptide (Trica-AVP; CLITNCPRGamide) and an ITP-related peptide (Trica-ITP). No evidence was found for the presence of 'A' allatostatins (Y/FxFGLamides) or corazonin, either in T. molitor, or in the genome of T. castaneum.

Neuropeptides and neurohormones are among the more diverse and functionally important classes of cell-to-cell signaling molecules involved in animal development and behavior. Less is known about the hormones and neuropeptides of the red flour beetle, Tribolium castaneum, than many other insects. However, the genomic information becoming available from this organism presents an opportunity to identify multiple neuropeptide and hormone genes, and hence their associated protein precursors. Using similarity-based prediction, we report new neuropeptides and hormone precursors from T. castaneum, bringing the number of annotated precursors to 37. We identified one prohormone (SVDPIDGDLIG-containing) having little similarity to other insect prohormones. The conversion of the protein precursors into bioactive peptides requires a suite of processing enzymes and a number of enzymatic steps; using the web-based NeuroPred application and similarity-based bioinformatics approaches, we predict 132 likely peptides that may result from the enzymatic processing of these gene products.

4,8-Dimethyldecanal (4,8-DMD) is the aggregation pheromone produced by male red flour beetles (RFB), Tribolium castaneum. To elucidate the biosynthetic origin of 4,8-DMD, the following studies were performed: (1) effects of juvenile hormone (JH) III, and pathway inhibitors mevastatin, an inhibitor of the mevalonate pathway, and 2-octynoic acid, an inhibitor of the fatty acid pathway, were tested to determine whether 4,8-DMD is derived from the fatty acid pathway or the mevalonate pathway; (2) incorporation of 13C-labeled acetate, propionate, and mevalonolactone into 4,8-DMD was measured to directly determine the biosynthetic origin of 4,8-DMD; and (3) incorporation of deuterium-labeled precursors, including 2-methylbutanoate (C5D), 4-methylhexanoate (C7D), 2,6-dimethyloctanoate (C10D), and 4,8-dimethyldecanoate (C12D) was tested to determine whether 4,8-DMD is biosynthesized in the sequence Ac-Pr-Ac-Pr-Ac (Ac; acetate, Pr; propionate). JH III was topically applied to males at various doses. Inhibitors and isotopically labeled substrates were administered orally by feeding the beetles flour treated with the substrates of interest, after which volatiles were collected from both sexes of RFBs. The amount of 4,8-DMD produced was significantly reduced with increasing doses of JH III. Also, 2-octynoic acid inhibited the production of 4,8-DMD, but mevastatin did not. Exposure of RFBs to [1-(13)C]acetate and [1-(13)C]propionate, but not [2-(13)C]mevalonolactone, resulted in incorporation of the labeled compounds into 4,8-DMD. RFBs fed flour treated with deuterium-labeled C5D, C10D, and C12D, but not C7D, incorporated these compounds into 4,8-DMD. The findings that the production of 4,8-DMD was inhibited by 2-octynoic acid but unaffected by mevastatin, combined with the high incorporation of [1-(13)C]acetate and [1-(13)C]propionate into 4,8-DMD and the incorporation of deuterated precursors, unambiguously demonstrated that 4,8-DMD is of fatty acid rather than terpene biosynthetic origin, and that the biosynthesis of 4,8-DMD proceeds in the sequence Ac-Pr-Ac-Pr-Ac.

We are characterizing the cuticular proteins of Tribolium castaneum (Herbst) (Coleoptera:Tenebrionidae) to determine their role in the function of the exoskeleton. Based on qualitative analyses of cuticles, we focused on the sodium dodecyl sulfate (SDS)-extractable proteins. A small-scale cuticle "mini-prep" procedure was devised that yields preparations virtually free of contaminating cellular material compared to hand-dissected preparations, as assessed by fluorescent microscopy using DAPI to stain nuclei. Proteins extracted in 1% SDS from various developmental stages (last larval instar, pupal, adult) were analyzed by one-dimensional denaturing polyacrylamide gel electrophoresis and by two-dimensional gel electrophoresis. The cuticular protein profiles show both similarities and differences among the stages examined. The amino acid composition, glycosylation, and partial amino acid sequence of several abundant cuticular proteins indicate similarity to cuticular proteins of other insects.

Benzoquinones were extracted from flour beetles by rinsing them for 8 min in methanol followed by homogenization in fresh methanol. This procedure recovered > 96% of the total benzoquinones from both species, with the methanolic rinse and supernatant representing the "surface" and "total" benzoquinones. As determined by UV/VIS spectrometry and reversed-phase HPLC, the methanolic rinse contained methyl- and ethyl-1,4-benzoquinone (MBQ and EBQ), but no substituted hydroquinones, The methanolic supernatant contained MBQ and EBQ, and methyl- and ethyl-hydroquinone. When stored at -20 degrees C for 72 hr, the chemical composition of the methanolic rinse did not change, but the composition of the methanolic homogenate did change. Notably, the amounts of benzoquinones in the methanolic supernatant decreased during storage. The method described represents an improvement over those described previously in that it uses less hazardous solvents for extraction (methanol vs more non-polar solvents such as hexane) and allows for the differentiation and quantification of the surface and total benzoquinones of these beetles.