PLA2 mediates the innate immune response in Asian corn borer, Ostrinia furnacalis

The eicosanoid signaling pathway mediates insect immune reactions to a wide range of stimuli. This pathway begins with the biosynthesis of arachidonic acid (AA) from the hydrolysis of phospholipids catalyzed by phospholipase A₂ (PLA₂ ). We report here that the PLA₂ inhibitor, dexamethasone (DEX), impaired the innate immune response including nodulation, encapsulation, and melanization in Ostrinia furnacalis larvae, while AA partially reversed these effects of DEX. We cloned a full-length complementary DNA encoding a PLA₂ , designated as OfsPLA₂ , from O. furnacalis. The open reading frame of OfsPLA₂ encodes a 195-amino acid residue protein with a 22-residue signal peptide. Sequence alignment analyses indicated that O. furnacalis PLA₂ might be a Group III secretory PLA₂ . The highest transcript levels of OfsPLA₂ were detected in the fat body, and its transcript levels increased dramatically after infection with Escherichia coli, Micrococcus luteus, or Beauveria bassiana. Recombinant OfsPLA₂ significantly induced prophenoloxidase (PPO) activation in larval hemolymph in the presence of Ca²⁺ and encapsulation of agarose beads. Injection of recombinant OfsPLA₂ into larvae resulted in increased transcript levels of attacin, defencin, and moricin-3 genes. Our results demonstrate the involvement of the eicosanoid signaling pathway in the innate immune response of O. furnacalis larvae and provide new information about the roles of O. furnacalis secretory PLA₂ in activating PPO and antimicrobial peptide production.

Effects of freeze-thawing cycles on desorption behaviors of PAH-contaminated soil in the presence of a biosurfactant: a case study in western Canada

Many regions in Canada are facing increasing environmental threats posed by oil and gas exploitation and transportation. These contaminated lands are inevitably subjected to seasonal and diurnal freeze-thawing cycles (FTCs). However, knowledge about the effect of FTCs on the behaviours of hydrophobic contaminants during the aging process of soil is limited. This study investigated the desorption characteristics of phenanthrene in aging soils in the presence of the biosurfactant rhamnolipid under diurnal and seasonal FTC treatments. It was found that the presence of rhamnolipid in soil during the aging process was able to increase the desorption efficiency of phenanthrene. In the presence of rhamnolipid above 100 mg L^-1, FTCs could inhibit the sequestration of phenanthrene. Soil moisture and rhamnolipid concentration are two major factors affecting this effect. High moisture content and FTC frequency could lead to lower desorption in the early stage of FTCs due to the increased specific surface area. The sequestration of phenanthrene was less effectively hindered under seasonal FTCs than diurnal FTCs. The results from this study have important implications for understanding the role of surfactants in cold-region soil aging, and for the improvement of site remediation strategies of PAH contaminated soil in cold regions.

Variations in fuel use in the flight muscles of wing-dimorphic Gryllus firmus and implications for morph-specific dispersal

Although a considerable amount of information is available on tradeoffs in wing-polymorphic insects, only limited data are available on the relationship between flight and biochemical variation within species. In the current study, we compared the biochemical basis in the dorsolongitudinal flight muscle of the wing-dimorphic sand cricket, Gryllus firmus Scudder, with respect to tradeoffs in energy resources related to morph-specific flight, including glycogen, trehalose, and triglycerides. Our results show that levels of glycogen and trehalose in long-winged adults (LW[f]) were significantly higher before dispersal, on days 5 and 7. Considering that this is the period during which long-winged adults are flight-capable, these results suggest that both glycogen and trehalose are important to flight. However, levels of triglycerides in short-winged crickets (SW) were higher than in long-winged crickets, suggesting that triglycerides are not directly related to initial flight. In SW adults, triglyceride content on days 5 and 7 was significantly higher just before lights off than at the same time on day 1 or at any other time after lights on all other days. This suggests that triglycerides are probably related to reproductive behaviors, such as mating and oviposition, in the SW morph. In addition, flight muscle water content was significantly lower in the LW(f) morph than in the SW morph.

[Effects of ultrasound induction on genomic DNA of housefly larvae]

The genomic DNA of housefly larvae was extracted after ultrasound induction, and the structure was analyzed by UV, fluorescence, IR and 1H NMR. The 3'-end of attacin gene was sequenced and compared by means of PCR. All the results indicated that ultrasound induction can destroy the second structure and the base stacking of genomic DNA of housefly larvae, which will result in mismatch repair during DNA duplication and finally change the sequence of DNA, but it has no significant effect on chemical groups and chemical band of genomic DNA.

[Molecular cloning and expression of Attacin from housefly (Musca domestica)]

The antimicrobial peptides of insect are the main components of their non-specific immune system, and play a major role in the defense against the foreign disease-related microbes. In this report, a full length cDNA of Attacin, an insect antimicrobial peptide was cloned from housefly (Musca domestica) by homology cloning approach in combine with 3' and 5' RACE. Sequence analysis and phylogenetical study showed that this cDNA contained 778 nucleotides, with a 627 bp open reading frame (ORF) flanked with a 44 bp 5'UTR and a 107 bp 3'UTR. The encoded 208 amino acids housefly Attacin shared a high similarity of 50%-70% with that of the other dipterous insects. In addition, the phylogenetical analysis also indicated that the Attacin from housefly was in the same branch with those of other species, suggesting that they come from the same ancestor. The expression of Attacin transcript was measured by semi-quantitive RT-PCR. The results demonstrated that the expression of housefly Attacin is inducible, and that the level varies with the time of induction and the kinds of pathogens.