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The 14-3-3 gene plays important role in many biological processes, including cell survival, apoptosis, and signal transduction. However, function of the 14-3-3 homologous gene in Musca domestica remains unclear. Here, we identified and characterized the 14-3-3ζ of M. domestica. We found that Md14-3-3ζ gene was highly homologous with other close insects. The qRT–PCR analysis revealed that the Md14-3-3ζ was highly expressed in adults, and was expressed predominantly in hemocytes and fat body. Meanwhile, the expression of Md14-3-3ζ was up-regulated after injecting Escherichia coli and Staphylococcus aureus. Moreover, the recombinant protein rMd14-3-3ζ strongly inhibits the growth of E. coli and S. aureus. Notably, the rMd14-3-3ζ inhibits E. coli and S. aureus by permeating the cell membrane. Taken together, our findings suggested that Md14-3-3ζ is involved in the immune response against bacteria through damaging the cell membrane.

Insects have the phenomenon of immune priming by which they can have enhanced protection against reinfection with the same pathogen, and this immune protection can be passed on to their offspring, which is defined as "trans-generational immune priming (TGIP)." But whether housefly possesses TGIP is still unclear. Therefore, we used the housefly as the insect model and

Many entomopathogens regulate the development of their insect hosts. However, the influence of mermithid nematodes on the development of their host remains unclear. In the current study, we provide insights into how Ovomermis sinensis parasitism affects the development of Helicoverpa armigera. We observed that O. sinensis arrests host development, as evidenced by the reduced body size and failure of Helicoverpa armigera to pupate. Moreover, midgut replacement of the host was significantly blocked by parasitism. Furthermore, juvenile hormone (JHIII) titers of the host were dramatically elevated by parasitism, but JH esterase (JHE) activities were strongly inhibited. By contrast, steroid hormone (20-hydroxyecdysone, 20E) titers of the host were significantly depressed by parasitism on days 4-6. The expression profiles of hormone-related genes in the host also showed similar patterns with the hormone titer. For this reason, rescue experiments were performed by injecting 20E and JHIII into developmentally arrested hosts. Notably, the midgut replacement of the host was rescued by the injection of 20E, whereas JHIII injection resulted in negative effects. Altogether, O. sinensis arrests H. armigera midgut replacement by reducing 20E and maintaining JH, thereby causing developmental arrests. Our study is the first report of the possible mechanism of mermithid nematodes in regulating insect development.

Chitinases are hydrolytic enzymes that play important roles in chitin degradation during the insect development process, and thus are considered as the potential targets for pest management. Here, we identified and characterized the group VII chitinase gene from health pest Musca domestica (MdCht2). We found that MdCht2 was 1932 bp in length with an open reading frame of 1530 bp, which encodes a polypeptide of 509 amino acid residues. Phylogenetic analysis showed that MdCht2 gene was homologs with other closed insects, and belong to the group VII chitinases. Moreover, Real-time PCR analysis indicated that MdCht2 mRNA was highly expressed in pupa stage, as well as in integument and trachea. However, RNAi-mediated knockdown of MdCht2 resulted in high mortality rates and abnormal eclosion. Therefore, we hypothesized that MdCht2 was a crucial gene required for housefly development, which was supported by the transcription level of MdCht2 could be induced by 20-hydroxyecdysone (20E), and the dsMdCht2 could resulted in decrease of the chitinase activity and increase of the chitin content. Taken together, our findings suggested that MdCht2 regulated the chitin content via chitinases, thereby leading to abnormal development. Our results provide a potential target for M. domestica management.

The mitochondrial genome (mitogenome) can provide information on genomic structure and can also be useful for phylogenetic analysis and evolutionary biology. A complete mitogenome sequence of a model nematode species, Caenorhabditis remanei , was determined. This mitogenome was 13,977 base pairs (bp) in length and contained 12 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, 2 ribosomal RNA genes, and non-coding regions. The nucleotide composition of the C. remanei mitogenome (heavy strand) was heavily biased toward A and T, with the overall A + T content was 77.46%. This bias had strong effects on the codon usage and relative synonymous codon usage in the PCGs. Thus, among the 12 PCGs, ATT and TAG were the most frequently used initiation and termination codons, respectively. In C. remanei , none of the mitogenome tRNAs, consistent with findings in other nematodes, could be folded into the canonical cloverleaf secondary structure, with 20 tRNAs lacking the TΨC (thymidine, pseudouridine, and cytidine) arm and two serine tRNAs ( trn S) missing the dihydrouracil (DHU) arm. In addition to the two large non-coding region, the AT-rich region and a non-coding region located between the nad4 and cox1 genes, several small non-coding intergenic spacers(INGS) was also detected in the C. remanei mitogenome. Comparison of the C. remanei mitogenome with those of four other Caenorhabditis species showed that these mitogenomes mainly differed in their non-coding regions. Finally, phylogenetic relationships among the five Caenorhabditis species were reconstructed based on the concatenated amino acid sequences of the 12 PCGs using the maximum likelihood and Bayesian inference methods, and the results supported the morphological classification and molecular analysis data from earlier studies.

Ovomermis sinensis (Nematoda: Mermithidae) is an entomophilic nematode and a potential biocontrol agent of lepidopteran pests, including Helicoverpa armigera. The sex ratio of a species can be used to regulate the size of the reproductive population. Parasitic load, parasitic period, host instar, and body size were examined to identify factors affecting the O. sinensis sex ratio. We tested the hypothesis that the O. sinensis sex ratio is correlated with host nutrient supply and the nutrients absorbed by the nematodes. The results show that the proportion of male O. sinensis increased with parasitic load but decreased with host instars and body size. Moreover, the parasitic period of males was significantly shorter than that of females. However, all the factors (host and nematodes) affecting the sex ratio were significantly modified by restricting the host diet, which increased the proportion of males. In turn, juveniles that absorbed fewer nutrients tended to develop into males. Taken together, ou...

Ovomermis sinensis is a potentially-valuable nematode for controlling insect pests. The parasitic stage of the nematode absorbs nutrients in its host's hemolymph to maintain its growth development and then kills the host when it emerges. At present, little known about its reproductive development, particularly the responsible molecular mechanism. More detailed research on the genes of reproductive development will not only help us understand the mechanisms underlying sex differentiation in the nematode, but would also be valuable for successfully cultivating them in vitro and using them for biocontrol. In this study, we used the homology cloning method to clone the full-length cDNA of a DEAD-box family gene (Oslaf-1) from O. sinensis. Then, using qRT-PCR technology to detect the expression pattern of the Oslaf-1 gene at different development stages and tissues, the gene was found to be highly expressed in the post-parasitic stage (P < 0.01) and ovarian (P < 0.05) of O. sinensis. Western blot analysis showed the same result that the gene is associated with gonadal development and function, but is not gonad-specific. In situ hybridization further demonstrated that the gene is widely expressed in early embryos and is mainly distributed in the gonadal area. However, the signal was mainly concentrated in the reproductive primordia in pre-parasitic juveniles. RNA interference (RNAi) studies revealed that the sex ratio of O. sinensis soaked in dsRNA of Oslaf-1 was not statistically different than the gfp dsRNA treated groups. Our results suggest that Oslaf-1 may play a vital role in the reproductive systems of the nematode. In addition, we speculate that the Oslaf-1 gene plays an important role during embryonic development and that it occurs and develops in the gonads of pre-parasitic juveniles of O. sinensis.