ABSTRACT
OBJECTIVE: Livestock droppings cause some environmental problems, but they have the potential to be used as effective biomass resources. The black soldier fly (BSF), Hermetia illucens (Diptera: Stratiomyidae), is suitable for efficiently processing such resources. By using BSF larvae for the disposal of livestock droppings, we can obtain two valuable products: protein resources and organic fertilizer. However, there is insufficient research on the digestive enzymes suitable for processing this waste. Here, we aimed to construct an efficient BSF processing system using livestock droppings, and we explored the digestive enzymes involved in this process. RESULTS: First, we investigated the characteristics of transcripts expressed in the midgut of BSF larvae and found that immune response-related genes were expressed in the midgut. Then, we investigated digestive enzymes and identified a novel serine protease, HiBrachyurin, whose mRNA was highly expressed in the posterior midgut when BSF larvae fed on horse droppings. Despite the low protein content of horse droppings, larvae that fed on horse droppings accumulated more protein than those in the other groups. Therefore, HiBrachyurin may contribute to digestibility in the early stage of protein degradation in BSF larvae fed on horse droppings.
Subject(s)
Diptera , Larva , Serine Proteases , Animals , Diptera/genetics , Diptera/metabolism , Diptera/enzymology , Larva/metabolism , Larva/genetics , Horses , Serine Proteases/metabolism , Serine Proteases/genetics , Insect Proteins/metabolism , Insect Proteins/genetics , FecesABSTRACT
Copidosoma floridanum is a cosmopolitan species and an egg-larval parasitoid of the Plusiine moth. C. floridanum has a unique development mode called polyembryony, in which over two thousand genetically identical embryos are produced from a single egg. Some embryos develop into sterile soldier larvae precociously, and their emergence period and aggressive behavior differ between the US and Japanese C. floridanum strains. Genome sequencing expects to contribute to our understanding of the molecular bases underlying the progression of polyembryony. However, only the genome sequence of the US strain generated by the short-read assembly has been reported. In the present study, we determined the genome sequence of the Japanese strain using Pacific Biosciences high-fidelity reads and generating a highly contiguous assembly (552.7 Mb, N50: 17.9 Mb). Gene prediction and annotation identified 13,886 transcripts derived from 10,786 gene models. We searched the genomic differences between US and Japanese strains. Among gene models predicted in this study, 100 gene loci in the Japanese strain had extremely different gene structures from those in the US strain. This was accomplished through functional annotation (GGSEARCH) and long-read sequencing. Genomic differences between strains were also reflected in amino acid sequences of vasa that play a central role in caste determination in this species. The genome assemblies constructed in this study will facilitate the genomic comparisons between Japanese and US strains, leading to our understanding of detailed genomic regions responsible for the ecological and physiological characteristics of C. floridanum.
Subject(s)
Molecular Sequence Annotation , Wasps , Animals , Wasps/genetics , Genome, Insect , Genomics/methods , Japan , East Asian PeopleABSTRACT
We detected enzymatic activity that generates 20-nucleotide (nt) RNA from double-stranded RNAs (dsRNAs) in crude extracts prepared from various silkworm (Bombyx mori) organs. The result using knocked-down cultured cells indicated that this dicing activity originated from B. mori Dicer-2 (BmDcr2). Biochemical analyses revealed that BmDcr2 preferentially cleaves 5'-phosphorylated dsRNAs at the 20-nt site-counted from the 5'-phosphorylated end-and required ATP and magnesium ions for the dicing reaction. This is the first report of the biochemical characterization of Dicer-2 in lepidopteran insects. This enzymatic property of BmDcr2 in vitro is consistent with the in vivo small interfering RNA profile in virus-infected silkworm cells.
Subject(s)
Bombyx , RNA, Double-Stranded , Ribonuclease III , Animals , Bombyx/genetics , Bombyx/metabolism , Insect Proteins/metabolism , Insect Proteins/genetics , Larva/metabolism , Larva/genetics , Larva/growth & development , Magnesium/metabolism , Ribonuclease III/metabolism , Ribonuclease III/genetics , RNA, Double-Stranded/metabolism , RNA, Small Interfering/metabolismABSTRACT
BACKGROUND: The frass of several herbivorous insect species has been utilised as natural medicines in Asia; however, the metabolite makeup and pharmaceutical activities of insect frass have yet to be investigated. Oligophagous Papilionidae insects utilise specific kinds of plants, and it has been suggested that the biochemicals from the plants may be metabolised by cytochrome P450 (CYP) in Papilionidae insects. In this study, we extracted the components of the frass of Papilio machaon larvae reared on Angelica keiskei, Oenanthe javanica or Foeniculum vulgare and examined the biological activity of each component. Then, we explored the expression of CYP genes in the midgut of P. machaon larvae and predicted the characteristics of their metabolic system. RESULTS: The components that were extracted using hexane, chloroform or methanol were biochemically different between larval frass and the host plants on which the larvae had fed. Furthermore, a fraction obtained from the chloroform extract from frass of A. keiskei-fed larvae specifically inhibited the cell proliferation of the human colon cancer cell line HCT116, whereas fractions obtained from the chloroform extracts of O. javanica- or F. vulgare-fed larval frass did not affect HCT116 cell viability. The metabolites from the chloroform extract from frass of A. keiskei-fed larvae prevented cell proliferation and induced apoptosis in HCT116 cells. Next, we explored the metabolic enzyme candidates in A. keiskei-fed larvae by RNA-seq analysis. We found that the A. keiskei-fed larval midgut might have different characteristics from the O. javanica- or F. vulgare-fed larval metabolic systems, and we found that the CYP6B2 transcript was highly expressed in the A. keiskei-fed larval midgut. CONCLUSIONS: These findings indicate that P. machaon metabolites might be useful as pharmaceutical agents against human colon cancer subtypes. Importantly, our findings show that it might be possible to use insect metabolic enzymes for the chemical structural conversion of plant-derived compounds with complex structures.
Subject(s)
Butterflies , Colonic Neoplasms , Animals , Humans , Butterflies/metabolism , Larva/metabolism , Chloroform , HCT116 Cells , Cytochrome P-450 Enzyme System/genetics , Cytochrome P-450 Enzyme System/metabolism , Plant Extracts/pharmacology , Pharmaceutical PreparationsABSTRACT
(1) The global population is projected to reach a staggering 9.8 billion people by the year 2050, leading to major concerns about food security. The necessity to increase livestock production is inevitable. The black soldier fly (BSF) is known for its ability to consume a wide range of organic waste, and BSF larvae have already been used as a partial substitute for fishmeal. In contrast, the use of antibiotics in livestock feed for growth promotion and prophylaxis poses a severe threat to global health owing to antimicrobial resistance. Insect antimicrobial peptides (AMPs) have shown the potential to rapidly disrupt target bacterial membranes, making bacterial resistance to AMPs a less likely concern. (2) In this study, we explored various methods for stimulating AMP synthesis in BSF larvae and found that thermal injury effectively induced the production of various AMP types. Additionally, we investigated the activation of innate immune response pathways that lead to AMP production following thermal injury. (3) Interestingly, thermal injury treatment, although not involving bacteria, exhibited a similar response to that observed following Gram-positive bacterial infection in eliciting the expression of AMP genes. (4) Our findings offer support for the industrial use of BSF to enhance livestock production and promote environmental health.
Subject(s)
Antimicrobial Peptides , Diptera , Animals , Humans , Larva , Diptera/physiology , Bacteria , LivestockABSTRACT
Insects must periodically replace their old cuticle/exoskeleton with a new one in a process called molting or ecdysis to allow for continuous growth through sequential developmental stages. Many RNA interference (RNAi) studies have demonstrated that certain chitinases (CHTs) play roles in this vital physiological event because knockdown of these CHT genes resulted in developmental arrest during the ensuing molting period in several insect species. In this research we analyzed the functions of group I (MaCHT5) and group II (MaCHT10) CHT genes in molting of the Japanese pine sawyer, Monochamus alternatus, an important forest pest known as a major vector of the pinewood nematode. Real-time qPCR revealed that these two CHT genes differ in their expression patterns during late stages of development. Depletion of either MaCHT5 or MaCHT10 transcripts by RNAi resulted in lethal larval-pupal and pupal-adult molting defects depending on the double-stranded RNA (dsRNA) injection timing during development. The insects were unable to shed their old cuticle and died. Furthermore, transmission electron microscopic analysis revealed that, unlike dsEGFP-treated controls, dsMaCHT5- and dsMaCHT10-treated pharate adults exhibited a failure of degradation of the endocuticular layer of their old pupal cuticle, retaining nearly intact horizontal chitinous laminae and vertical pore canal fibers. Both enzymes were indispensable for complete turnover of the chitinous old endocuticle, which is critical for insect molting. The possible functions of two spliced variants of MaCHT10, namely, MaCHT10a and MaCHT10b, are also discussed. Our results add to the knowledge base for further functional studies of insect chitin catabolism by revealing the relative importance of both MaCHT5 and MaCHT10 in chitin turnover with subtle differences in their action. These essential genes and their encoded proteins are potential targets to manipulate for controlling populations of M. alternatus and other pest insects.
Subject(s)
Chitinases , Coleoptera , Tribolium , Animals , Molting/genetics , Tribolium/genetics , Chitinases/genetics , Chitinases/metabolism , Chitin/metabolism , Wood/metabolism , Insect Proteins/genetics , Insect Proteins/metabolism , RNA InterferenceABSTRACT
BACKGROUND: The dung beetle Phelotrupes auratus is a holometabolous insect belonging to the order Coleoptera, and it is widely distributed in Japan. The P. auratus habitat depends on herbivores. P. auratus eats the dung of the herbivores and carries it underground for its young. In this process, herbivore droppings disappear from the ground, not only keeping the ground hygienic but also maintaining good soil conditions for plant growth. In this way, a rich ecosystem is maintained. In recent years, the population of P. auratus has decreased, and the main cause has been the decrease in grazing land. It seems that Japanese dung beetles are mainly dependent on herbivores for nutrient sources. However, the physiological relationship between herbivores and P. auratus has not been well investigated. Here, we investigated the nutritional metabolism system of P. auratus by performing whole gene expression analysis of individuals collected from two areas where the ecosystem is occupied by different herbivores. RESULTS: We obtained 54,635 transcripts from P. auratus from Nara Park and Cape Toi and identified 2,592 differentially expressed genes in the fat bodies of the Nara Park and Cape Toi groups. We annotated P. auratus transcripts using Homo sapiens and Drosophila melanogaster genes as references; 50.5% of P. auratus transcripts were assigned to H. sapiens genes, and 54.0% of P. auratus transcripts were assigned to D. melanogaster genes. To perform gene set enrichment analysis, we chose H. sapiens genes for P. auratus transcript annotation. Principal component analysis and gene set enrichment analysis revealed that the nutritional metabolism of P. auratus from Cape Toi might differ from that of P. auratus from Nara Park. CONCLUSION: We analyzed the nutritional metabolism system of P. auratus from Cape Toi and Nara Park and found that the characteristics of the nutritional metabolism process might depend on the plants consumed by the herbivores. Our findings will contribute to elucidating the relationships among habitat plants, herbivores, and dung decomposers and may aid in the maintenance of sustainable land health cycles.
Subject(s)
Coleoptera , Animals , Coleoptera/genetics , Herbivory , Ecosystem , Drosophila melanogaster , Plants/genetics , FecesABSTRACT
Next-generation sequencing has revolutionized entomological study, rendering it possible to analyze the genomes and transcriptomes of non-model insects. However, use of this technology is often limited to obtaining the nucleotide sequences of target or related genes, with many of the acquired sequences remaining unused because other available sequences are not sufficiently annotated. To address this issue, we have developed a functional annotation workflow for transcriptome-sequenced insects to determine transcript descriptions, which represents a significant improvement over the previous method (functional annotation pipeline for insects). The developed workflow attempts to annotate not only the protein sequences obtained from transcriptome analysis but also the ncRNA sequences obtained simultaneously. In addition, the workflow integrates the expression-level information obtained from transcriptome sequencing for application as functional annotation information. Using the workflow, functional annotation was performed on the sequences obtained from transcriptome sequencing of the stick insect (Entoria okinawaensis) and silkworm (Bombyx mori), yielding richer functional annotation information than that obtained in our previous study. The improved workflow allows the more comprehensive exploitation of transcriptome data and is applicable to other insects because the workflow has been openly developed on GitHub.
ABSTRACT
Transferrin-1 (Tsf1) is an extracellular insect protein with a high affinity for iron. The functions of Tsf1 are still poorly understood; however, Drosophila melanogaster Tsf1 has been shown to influence iron distribution in the fly body and to protect flies against some infections. The goal of this study was to better understand the physiological functions of Tsf1 in D. melanogaster by 1) investigating Tsf1 null phenotypes, 2) determining tissue-specific localization of Tsf1, 3) measuring the concentration of Tsf1 in hemolymph, 4) testing Tsf1 for bacteriostatic activity, and 5) evaluating the effect of metal and paraquat treatments on Tsf1 abundance. Flies lacking Tsf1 had more iron than wild-type flies in specialized midgut cells that take up iron from the diet; however, the absence of Tsf1 had no effect on the iron content of whole midguts, fat body, hemolymph, or heads. Thus, as previous studies have suggested, Tsf1 appears to have a minor role in iron transport. Tsf1 was abundant in hemolymph from larvae (0.4 µM), pupae (1.4 µM), adult females (4.4 µM) and adult males (22 µM). Apo-Tsf1 at 1 µM had bacteriostatic activity whereas holo-Tsf1 did not, suggesting that Tsf1 can inhibit microbial growth by sequestering iron in hemolymph and other extracellular environments. This hypothesis was supported by detection of secreted Tsf1 in tracheae, testes and seminal vesicles. Colocalization of Tsf1 with an endosome marker in oocytes suggested that Tsf1 may provide iron to developing eggs; however, eggs from mothers lacking Tsf1 had the same amount of iron as control eggs, and they hatched at a wild-type rate. Thus, the primary function of Tsf1 uptake by oocytes may be to defend against infection rather than to provide eggs with iron. In beetles, Tsf1 plays a role in protection against oxidative stress. In contrast, we found that flies lacking Tsf1 had a typical life span and greater resistance to paraquat-induced oxidative stress. In addition, Tsf1 abundance remained unchanged in response to ingestion of iron, cadmium or paraquat or to injection of iron. These results suggest that Tsf1 has a limited role in protection against oxidative stress in D. melanogaster.
Subject(s)
Drosophila melanogaster , Transferrin , Animals , Drosophila melanogaster/metabolism , Female , Iron/metabolism , Male , Oxidative Stress , Paraquat/toxicity , Phenotype , Transferrin/chemistryABSTRACT
The body form of holometabolous insects dramatically transforms from larval to adult stages during metamorphosis that occurs in the pupal stage. The larval disorganization and then new adult tissues are built up at this time. In motoneuron, larval neuronal cells degenerate, and new adult neurons are remodeled. Finally, adult neurons reconnect to new adult muscles. However, the factors that control metamorphosis have not yet been fully elucidated. Here, we show that an antioxidant enzyme, Tribolium castaneum superoxide dismutase 6 (TcSOD6), is secreted into the haemolymph and is required for proper movable legs during metamorphosis. TcSOD6 has a unique domain architecture and is mainly expressed in the pupal stage. The depletion of TcSOD6 expression in the pupa inhibits normal axon development and results in adults that display dysfunctional leg motions, suggesting that SOD6 expression is required for the development of properly movable legs. Therefore, we speculate that TcSOD6 might participate in some of the processes for larval neurons to be remodelled to new adult functions in the legs during metamorphosis, providing new insight into the evolution of SOD functions.
Subject(s)
Tribolium , Animals , Larva/genetics , Metamorphosis, Biological/physiology , Pupa , Superoxide Dismutase/genetics , Tribolium/geneticsABSTRACT
The DJ-1 gene is highly conserved across a wide variety of organisms and it plays a role in anti-oxidative stress mechanisms in cells. The red flour beetle, Tribolium castaneum, is widely used as a model insect species because it is easy to evaluate gene function in this species using RNA interference (RNAi). The T. castaneum DJ-1 (TcDJ-1) sequence is annotated in the T. castaneum genome database; however, the function and characteristics of the TcDJ-1 gene have not been elucidated. Here, we investigated the cDNA sequence of TcDJ-1 and partially characterized its function. First, we examined the TcDJ-1 amino acid sequence and found that it was highly conserved with sequences from other species. TcDJ-1 mRNA expression was higher in the early pupal and adult developmental stages. We evaluated oxidant tolerance in TcDJ-1 knockdown adults using paraquat and found that adults with TcDJ-1 knockdown exhibited increased sensitivity to paraquat. Our findings show that TcDJ-1 has an antioxidant function, as observed for DJ-1 from other insects. Therefore, these results suggest that TcDJ-1 protects against oxidative stress during metamorphosis.
ABSTRACT
OBJECTIVE: Insects are the most evolutionarily successful groups of organisms, and this success is largely due to their flight ability. Interestingly, some stick insects have lost their flight ability despite having wings. To elucidate the shift from wingless to flying forms during insect evolution, we compared the nutritional metabolism system among flight-winged, flightless-winged, and flightless-wingless stick insect groups. RESULTS: Here, we report RNA sequencing of midgut transcriptome of Entoria okinawaensis, a prominent Japanese flightless-wingless stick insect, and the comparative analysis of its transcriptome in publicly available midgut transcriptomes obtained from seven stick insect species. A gene enrichment analysis for differentially expressed genes, including those obtained from winged vs wingless and flight vs flightless genes comparisons, revealed that carbohydrate metabolic process-related genes were highly expressed in the winged stick insect group. We also found that the expression of the mitochondrial enolase superfamily member 1 transcript was significantly higher in the winged stick insect group than in the wingless stick insect group. Our findings could indicate that carbohydrate metabolic processes are related to the evolutionary process through which stick insects gain the ability of flight.
Subject(s)
Gene Expression Profiling , Insecta , Animals , Insecta/genetics , Sequence Analysis, RNA , TranscriptomeABSTRACT
Phytophagous insect larvae feed on plants containing secondary metabolic products with biological activity against other predatory organisms. Phytophagous insects can use their specialised metabolic systems to covert these secondary metabolic products into compounds with therapeutic properties useful to mankind. Some Asians drink tea decoctions made from phytophagous insect frass which is believed to be effective against inflammatory diseases. However, insects that can convert plant-derived secondary metabolic products into useful human therapeutic agents remain poorly studied. Here, we constructed the TUATinsecta database by integrating publicly plant/insect datasets for the purpose of selecting insect species. Using TUAT-insecta we selected the Asian swallowtail butterfly, Papilio xuthus larvae fed on several species of Rutaceous plants and examined whether the plant-derived secondary metabolites, especially those present in frass, were chemically altered or not. We extracted metabolic products from frass using three organic solvents with different polarities, and evaluated solvent fractions for their cytotoxic effects against several human cell lines. We found that chloroform frass extracts from P. xuthus larvae fed on Poncirus trifoliata leaves contained significant cytotoxic activity. Our findings demonstrate that screening of insect species using the 'TUATinsecta' database provides an important pipeline for discovering novel therapeutic agents that might be useful for mankind.
Subject(s)
Biological Products/chemistry , Databases, Factual , Entomology/methods , Insecta/chemistry , Animals , Butterflies , Cell Proliferation , Cell Survival , Citrus , Drug Discovery , Feces/chemistry , HeLa Cells , Hep G2 Cells , Humans , Inflammation , Inhibitory Concentration 50 , Larva , Plant Leaves/chemistry , PoncirusABSTRACT
BACKGROUND: Polyembryony is defined as the formation of several embryos from a single egg. This phenomenon can occur in humans, armadillo, and some endoparasitoid insects. However, the mechanism underlying polyembryogenesis in animals remains to be elucidated. The polyembryonic parasitoid wasp Copidosoma floridanum oviposits its egg into an egg of the host insect; eventually, over 2000 individuals will arise from one egg. Previously, we reported that polyembryogenesis is enhanced when the juvenile hormone (JH) added to the culture medium in the embryo culture. Hence, in the present study, we performed RNA sequencing (RNA-Seq) analysis to investigate the molecular mechanisms controlling polyembryogenesis of C. floridanum. Functional annotation of genes is not fully available for C.floridanum; however, whole genome assembly has been archived. Hence, we constructed a pipeline for gene functional annotation in C. floridanum and performed molecular network analysis. We analyzed differentially expressed genes between control and JH-treated molura after 48 h of culture, then used the tblastx program to assign whole C. floridanum transcripts to human gene. RESULTS: We obtained 11,117 transcripts in the JH treatment group and identified 217 differentially expressed genes compared with the control group. As a result, 76% of C. floridanum transcripts were assigned to human genes. Gene enrichment analysis revealed genes associated with platelet degranulation, fatty acid biosynthesis, cell morphogenesis in the differentiation and integrin signaling pathways were fluctuated following JH treatment. Furthermore, Cytoscape analysis revealed a molecular interaction that was possibly associated with polyembryogenesis . CONCLUSIONS: We have constructed a pipeline for gene functional annotation of C. floridanum, and identified transcripts with high similarity to human genes during early embryo developmental. Additionally, this study reveals new molecular interactions associated with polyembryogenesis; these interactions could indicate the molecular mechanisms underlying polyembryony. Our results highlight the potential utility of molecular interaction analysis in human twins.
Subject(s)
Embryonic Development/genetics , Wasps/embryology , Wasps/genetics , Animals , Embryonic Development/drug effects , Genes , Humans , Juvenile Hormones/pharmacology , RNA-Seq , Wasps/metabolismABSTRACT
Perhaps, oxidative stress progresses pupation in some Lepidopteran insects; however, the reasons for this remain obscure. In our previous study, we clarified Bombyx mori SOD1 (BmSOD1) and B. mori SOD2 (BmSOD2) proteins respond in common to ultraviolet irradiation (UV) oxidative stress and metamorphosis. This result strongly suggested pupation initiates by oxidative stress and might mediate by down-regulation of expression of BmSOD1 and BmSOD2 proteins. Thus, we examined about these relationships in B. mori in this study. In the microarray data reanalysis, we found the Notch signaling pathways as the common pathways in pupation and UV oxidative stress in B. mori. Also, we showed a molting hormone, 20-hydroxyecdysone, leads not only generation of superoxide but also downregulation of the expression of BmSOD proteins during pupation in B. mori. Our findings can contribute to a deeper understanding of how biological defense systems work against environmental oxidative stress.
Subject(s)
Bombyx/growth & development , Down-Regulation/radiation effects , Insect Proteins/metabolism , Larva/metabolism , Oxidative Stress/radiation effects , Pupa/metabolism , Superoxide Dismutase-1/metabolism , Superoxide Dismutase/metabolism , Animals , Ecdysterone/metabolism , Gene Expression Regulation, Developmental , Reactive Oxygen Species/metabolism , Receptors, Notch/metabolism , Ultraviolet RaysABSTRACT
Copidosoma floridanum is a polyembryonic, caste-forming, wasp species. The ratio of investment in different castes changes with environmental stressors (e.g. multi-parasitism with competitors). The vasa gene was first identified in Drosophila melanogaster as a germ-cell-determining factor, and C. floridanum vasa (Cf-vas) gene positive cells have been known to develop into reproductive larvae. Cf-vas seems to control the ratio of investment in C. floridanum larval castes. In this study, we identified environmental factors that control Cf-vas mRNA expression in Japanese C. floridanum by examining Cf-vas mRNA expression under competitor (Meteorus pulchricornis) venom stress; we treated the male and female morulae with M. pulchricornis venom. We also assessed the effects of multi-parasitism of Japanese C. floridanum with M. pulchricornis and found an increasing number of female soldier larvae. The results showed that several amino acid sequences differ between the Japanese and US Cf-vas. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) showed that Japanese Cf-vas mRNA is expressed in both male and female larvae and pupae, but mRNA expression decreases in adults. Cf-vas mRNA expression significantly decreased, while C. floridanum dronc (Cf-dronc) mRNA expression increased, in female morulae after M. pulchricornis venom treatment at 20â¯h and 0â¯h of the culture period, respectively. Females and males showed different Cf-vas or Cf-dronc mRNA expression after M. pulchricornis venom treatment. Therefore, M. pulchricornis venom could affect the ratio of investment in different female castes of Japanese C. floridanum by decreasing Cf-vas mRNA expression via apoptosis.
Subject(s)
DEAD-box RNA Helicases/genetics , Drosophila Proteins/genetics , Gene Expression Regulation/drug effects , Wasps/embryology , Amino Acid Sequence , Animals , Apoptosis/drug effects , Cell Lineage/drug effects , Cell Lineage/physiology , DEAD-box RNA Helicases/metabolism , Drosophila/genetics , Drosophila Proteins/metabolism , Female , Gene Expression Regulation/genetics , Gene-Environment Interaction , Germ Cells , Japan , Larva/physiology , Male , Morula/drug effects , Reproduction , Venoms/adverse effects , Wasps/genetics , Wasps/metabolismABSTRACT
Self-sacrifice is very rare among organisms. Here, we report a new and astonishing case of adaptive self-sacrifice in a polyembryonic parasitic wasp, Copidosoma floridanum. This wasp is unique in terms of its larval cloning and soldier larvae. Male clone larvae have been found to be killed by female soldier larvae, which suggests intersexual conflict between male and female larvae. However, we show here that mass killing is adaptive to all the killed males as well as the female soldiers that have conducted the killing because the killing increases their indirect fitness by promoting the reproduction of their clone sibs. We construct a simple model that shows that the optimal number of surviving males for both male and female larvae is very small but not zero. We then compare this prediction with the field data. These data agree quite well with the model predictions, showing an optimal killing rate of approximately 94-98% of the males in a mixed brood. The underlying mechanism of this mass kill is almost identical to the local competition for mates that occurs in other wasp species. The maternal control of the sex ratio during oviposition, which is well known in other hymenopterans, is impossible in this polyembryonic wasp. Thus, this mass kill is necessary to maximize the fitness of the female killers and male victims, which can be seen as an analogy of programmed cell death in multicellular organisms.
Subject(s)
Genetic Fitness , Models, Genetic , Reproduction/genetics , Sex Ratio , Wasps/physiology , Animals , Female , Larva/physiology , MaleABSTRACT
Insects are well adapted to changing environmental conditions. They have unique systems for eliminating reactive oxygen species (ROS). Superoxide dismutase (SOD) is a key enzyme that plays a primary role in removing ROS. Bombyx mori is a lepidopteran insect, whose body size is larger than the model insect Drosophila melanogaster, which enabled us to more easily examine gene expression at the tissue level. We searched B. mori SOD (BmSOD) genes using genome database, and we analyzed their function under different type of oxidative stress. Consequently, we identified four new types of BmSODs in addition to the three types already known. Two of the seven types had a unique domain architecture that has not been discovered previously in the SOD family, and they were expressed in different tissues and developmental stages. Furthermore, these BmSODs responded differently to several kinds of stressors. Our results showed that the seven types of BmSODs are likely to play different roles in B. mori; therefore, B. mori could be used to distinguish the functions of each SOD for resistance to oxidative stress that changes with the environmental conditions.
Subject(s)
Bombyx/enzymology , Insect Proteins/metabolism , Superoxide Dismutase/metabolism , Animals , Bombyx/genetics , Bombyx/growth & development , Gene Expression Regulation, Developmental , Gene Expression Regulation, Enzymologic , Genes, Insect , Insect Proteins/chemistry , Insect Proteins/genetics , Manduca/enzymology , Manduca/genetics , Oxidative Stress , Phylogeny , Protein Domains , RNA, Messenger/genetics , RNA, Messenger/metabolism , Reactive Oxygen Species/metabolism , Superoxide Dismutase/chemistry , Superoxide Dismutase/genetics , Tissue DistributionABSTRACT
OBJECTIVE: Hemolymph plays many important roles in the physiology of an insect throughout its lifetime; however, for small-bodied insects, studies are lacking because of the difficulties encountered while collecting hemolymph. The objective of our study was to develop a method to collect hemolymph plasma from various stages of Tribolium castaneum and to evaluate phenoloxidase activity in the plasma samples. We first designed a procedure for easily and quickly collecting clear hemolymph plasma from T. castaneum. RESULTS: By using this method, we collected approximately 5 µl plasma from 30 individuals at the larval, pupal or adult stages. And then, we studied the expression of phenoloxidase by performing western blot analysis of the plasma samples and found that phenoloxidase is present in hemolymph in each developmental stage. We also measured phenoloxidase activity in control plasma and plasma treated with Gram-positive bacteria, Micrococcus luteus. Phenoloxidase activity was greater in some of the M. luteus-treated plasma samples compared with control samples. Thus, we developed a method to collect hemolymph plasma that is suitable for studies of phenoloxidase activity.