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Polydnaviruses (PDVs) are obligatory symbionts of parasitoid wasps and play an important role in suppressing host immune defenses. Although PDV genes that inhibit host melanization are known in Microplitis bracovirus, the functional homologs in Cotesia bracoviruses remain unknown. Here, we find that Cotesia vestalis bracovirus (CvBV) can inhibit hemolymph melanization of its host, Plutella xylostella larvae, during the early stages of parasitization, and that overexpression of highly expressed CvBV genes reduced host phenoloxidase activity. Furthermore, CvBV‐7‐1 in particular reduced host phenoloxidase activity within 12 h, and the injection of anti‐CvBV‐7‐1 antibody increased the melanization of parasitized host larvae. Further analyses showed that CvBV‐7‐1 and three homologs from other Cotesia bracoviruses possessed a C‐terminal leucine/isoleucine‐rich region and had a similar function in inhibiting melanization. Therefore, a new family of bracovirus genes was proposed and named as C‐terminal Leucine/isoleucine‐rich Protein (CLP). Ectopic expression of CvBV‐7‐1 in Drosophila hemocytes increased susceptibility to bacterial repression of melanization and reduced the melanotic encapsulation of parasitized D. melanogaster by the parasitoid Leptopilina boulardi. The formation rate of wasp pupae and the eclosion rate of C. vestalis were affected when the function of CvBV‐7‐1 was blocked. Our findings suggest that CLP genes from Cotesia bracoviruses encoded proteins that contain a C‐terminal leucine/isoleucine‐rich region and function as melanization inhibitors during the early stage of parasitization, which is important for successful parasitization. [ABSTRACT FROM AUTHOR]

Odorant‐binding proteins (OBPs) are crucial in insect's olfactory perception, which participate in the initial step of odorant molecules transporting from the external environment to olfactory receptor neurons. To better understand the roles for OBPs in olfactory perception in Cotesia vestalis, a solitary larval endoparasitoid of diamondback moth, Plutella xylostella, we have comprehensively screened the genome of C. vestalis, and obtained 20 CvesOBPs, including 18 classic OBPs and two minus‐C OBPs. Motif‐pattern analysis indicates that the motifs of C. vestalis OBPs are highly conserved in Hymenoptera. The results of tissue expression analysis show that five OBPs (CvesOBP1/11/12/14/16) are highly expressed in male antennae, whereas six other OBP genes (CvesOBP7/8/13/17/18/19) are significantly transcriptionally enriched in female antennae. The results of RNA interference experiments for three most highly expressed OBP genes (CvesOBP17/18/19) in female antennae demonstrate that they are likely involved in parasitic processes of female wasps, as the wasps take a longer time to target the hosts when they are knocked down. [ABSTRACT FROM AUTHOR]

The adoption of pest-resistant transgenic plants to reduce yield losses and decrease pesticide use has been successful. To achieve the goal of controlling both chewing and sucking pests in a given transgenic plant, we generated transgenic tobacco, Arabidopsis, and rice plants expressing the fusion protein, AaIT/GNA, in which an insecticidal scorpion venom neurotoxin ( Androctonus australis toxin, AaIT) is fused to snowdrop lectin ( Galanthus nivalis agglutinin, GNA). Compared with transgenic tobacco and Arabidopsis plants expressing AaIT or GNA, transgenic plants expressing AaIT/GNA exhibited increased resistance and toxicity to one chewing pest, the cotton bollworm, Helicoverpa armigera. Transgenic tobacco and rice plants expressing AaIT/GNA showed increased resistance and toxicity to two sucking pests, the whitefly, Bemisia tabaci, and the rice brown planthopper, Nilaparvata lugens, respectively. Moreover, in the field, transgenic rice plants expressing AaIT/GNA exhibited a significant improvement in grain yield when infested with N. lugens. This study shows that expressing the AaIT/GNA fusion protein in transgenic plants can be a useful approach for controlling pests, particularly sucking pests which are not susceptible to the toxin in Bt crops. [ABSTRACT FROM AUTHOR]

A female-specific protein, vitellogenin (Vg), and its corresponding egg vitellin (Vt) are identified in the ectoparasitic wasp Nasonia vitripennis. Both native Vt and Vg have a molecular mass of about 350 kDa, which is composed of two subunits of approximately 190 kDa and 165 kDa under reducing and denaturing conditions (sodium dodecyl sulfate—polyacrylamide gel electrophoresis). An indirect sandwich enzyme-linked immunosorbent assay developed with both monoclonal and polyclonal antibodies against N. vitripennis Vt. Vg was first detected in the hemolymph on the 10th day after parasitism, and was first observed in oocytes on the 12th day. In adults deprived of food, the highest hemolymph Vg level occurred at the time of adult eclosion and the highest level of Vt in ovaries was found at 30 h after eclosion. In contrast, feeding adults with 20% sucrose resulted in the reduction of Vt uptake by ovaries and the extension of life span, but had little effect on Vg production. Deprived of hosts, starvation of female wasps had no significant effects on ovariole growth and oocyte maturation before the wasps died. However, starvation of female wasps supplied with hosts accelerated the wasps laying progeny into hosts, but resulted in a decrease of total progeny production by comparison with wasps fed with 20% sucrose. [ABSTRACT FROM AUTHOR]

The nutritional physiology of the diamondback moth, Plutella xylostella, larvae was examined after parasitization by the solitary endoparasitoids Cotesia vestalis or Diadegma semiclausum. Examinations were performed in two phases, one was examined at the time point of 24 h post-parasitization, and the other was done at the end of the 4th instar larvae of host. Rates of growth, food consumption, assimilation, excretion, and respiration were calculated as well as approximate digestibility and the rate ratios ECI (percent efficiency of conversion of ingested food to body substance), and ECD (percent efficiency of conversion of digested food to body substance). Parasitization by C. vestalis resulted in significant decrease in the rates of growth, feeding, excretion, assimilation, and respiration, but the final dry rate of respiration at the end of last larval stadium was elevated. The ECI and ECD were also reduced as the result of parasitization, but digestibility was increased. All these parameters in the larvae parasitized by D. semiclausum at 24 h post-parasitization were also significantly changed compared to the control; however, these differences were quantitatively, but not qualitatively before pupation, similar to those resulted from parasitization by C. vestalis. In spite of the similarities of the parasitism-induced effects caused by these endoparasitoids, the final metabolic rate, that is, the rate of intake of nutrients required to compensate for metabolism, was much lower in the larvae parasitized by C. vestalis than that of the larvae parasitized by D. semiclausum. All of the results discussed here will contribute toward explaining the different ways these two wasps regulate the parasitoid-host relationship. [ABSTRACT FROM AUTHOR]

Females of the solitary parasitoid Diadromus collaris (Insecta: Hymenoptera: Ichneumonidae) lay eggs in the pupae of Plutella xylostella (Lepidoptera: Plutellidae), and the venom is synchronously injected into hosts. The venom apparatus consists of two glandular tubules terminating in a common reservoir. A ductule connects the reservoir with the sting apparatus, by which the reservoir content enters the latter. Secretory units line the two glandular tubules. All secretory cells belong to dermal gland type III. Dermal gland cells in glandular tubules are more abundant and developed than those in the reservoir. There are extensive rough endoplasmic reticulum and electrondense vesicles, and the microvilli are well developed. By the cuticle-lined central funnel secretion products of secretory units reach the reservoir. Moreover, the secretory apparatus undergoes age-related changes. The secretory units in the venom gland are better developed and more vigorous 7 days after eclosion than those 1 day after eclosion; autolytic processes occur 15 days after eclosion, and the tissue of the reservoir is more prostrate 15 day after eclosion than those 1 day after eclosion. The ovipostion peak of this parasitoid, about 3–7 days after eclosion, corresponds with the period when the venom gland is highly developed in the life span of the wasp. [ABSTRACT FROM AUTHOR]

Partial DNA sequences of three genes, that is, mitochondrial large ribosomal subunit (16S), nuclear large ribosomal subunit (28S D2) and mitochondrial NADH1 dehydrogenase (NADH1) gene, were sequenced from different micro gastrine species (Braconidae: Micro gastrinae) collected fresh from paddy fields. The DNA sequences were used to determine the extent of sequence variation among species in order to evaluate the specific status of each species. Cladistic analysis was also used to infer a phylogenetic relationship among these species. The results showed that sequence divergence among species of the same genusCotesiawas much lower than those among different genera, such asCotesia, Exoryza and Apanteles; the sequence similarity of 16S rDNA andNADH1 genes betweenCotesiasp. and C.chiloniswas higher than that between C. sp. and C. ruficrus. Phylogenetic analyses suggested that four species of Cotesia were always grouped in the same clade regardless of using different analysis methods; Cotesia sp. and C. chilonis are more closely related to each other than to C. ruficrus, different from previous morphological results. Additionally, sequence analyses indicated that NADH1 gene has more parsimony informative characters than 28S rDNA D2 and 16S rDNA at the species-level analysis, indicating that NADH1 gene might be a useful marker for species-level analysis. [ABSTRACT FROM AUTHOR]