摘要: The efficiency of RNA interference (RNAi) varies substantially among different insect species. Rapid degradation of double-stranded RNA (dsRNA) by dsRNA-degrading nucleases (dsRNases) has been implicated to cause low RNAi efficiency in several insect species. In this study, we identified four dsRNase genes (OfdsRNase1, OfdsRNase2, OfdsRNase3 and OfdsRNase4) from the Asian corn borer (Ostrinia furnacalis) transcriptome database. Bioinformatic analyses showed that each deduced protein sequence contained endonuclease NS domains and signal peptides. Gene expression analysis revealed that OfdsRNase2 was exclusively expressed in the midgut of larvae. RNAi efficiency was investigated in 2-d-old fifth-instar larvae (high expression of dsRNase2) and 2-d-old pupae (low expression of dsRNase2) by feeding or injecting dsRNA targeting a marker gene that encodes the lethal giant larvae protein (OfLgl). Our results showed that OfLgl only partially silenced the expression of OfLgl in pupae, but not in larvae, suggesting that OfdsRNase2 could contribute to lower RNAi efficiency in larval stages. This hypothesis was supported by our RNAi-of-RNAi experiment using a tissue culture technique where the silencing efficiency against the reporter gene, OfHex1, was significantly improved after knockdown of OfdsRNase2. When double luciferase assays were performed to evaluate the role of the four dsRNases in vitro, only OfdsRNase2 expressed in S2 cells significantly affected RNAi efficiency by degrading dsRNA. Taken together, our results suggested that the degradation of dsRNA by OfdsRNase2 in the midgut contributed to low RNAi efficiency in O. furnacalis larvae.

摘要: Apolygus lucorumis the dominant pathogenic insect attackingBacillus thuringiensis(Bt) cotton in China. Additionally, 20-hydroxyecdysone (20E) has important functions in many biological processes, including insect reproduction. Phospholipase C (PLC), which is an essential enzyme for phosphoinositide metabolism, is involved in 20E signal transduction, but its function in 20E-mediated reproduction inA. lucorumremains unclear. In this study, 20E increasedAlPLC gamma transcription as well as the abundance and activity of the encoded protein during molting and metamorphosis. The 20E treatment also induced the considerable accumulation of two second messengers, inositol triphosphate and diacylglycerol. The expression levels of genes encoding vitellogenin (AlVg) and soluble trehalase (AlTre-1) were similar to those ofAlPLC gamma, and were upregulated in response to 20E. The silencing ofAlPLC gamma resulted in downregulated expression ofAlTre-1andAlVg. However, the silencing ofAlTre-1andAlVgdid not affectAlPLC gamma expression. Moreover, the silencing ofAlVgdid not alterAlTre-1expression. Furthermore, an examination of the insect specimens indicated thatAlPLC gamma is required for female adult reproduction, and that downregulated expression of this gene is associated with decreases in fecundity, adult longevity, and egg hatching rate as well as delayed oocyte maturation. We propose that 20E regulatesAlTre-1expression viaAlPLC gamma and affectsVgexpression as well as ovary development to facilitate the reproductive activities ofA. lucorumfemales.

摘要: Insect neuropeptides play an important role in regulating physiological functions such as growth, development, behavior and reproduction. We identified temperature-sensitive neuropeptides and receptor genes of the cotton whitefly, Bemisia tabaci. We identified 38 neuropeptide precursor genes and 35 neuropeptide receptors and constructed a phylogenetic tree using additional data from other insects. As temperature adaptability enables B. tabaci to colonize a diversity of habitats, we performed quantitative polymerase chain reaction with two temperature stresses (low = 4 degrees C and high = 40 degrees C) to screen for temperature-sensitive neuropeptides. We found many neuropeptides and receptors that may be involved in the temperature adaptability of B. tabaci. This study is the first to identify B. tabaci neuropeptides and their receptors, and it will help to reveal the roles of neuropeptides in temperature adaptation of B. tabaci.

摘要: The transcription factor grainy head (Grh) functions in the protection of the epithelium against the external environment by generating strongly adhesive layers, and this function is conserved in vertebrates and invertebrates. InDrosophila, the top model for holometabolous insects,Grhis necessary during embryonic development, epidermal differentiation, central nervous system specification and epithelial repair. However, the function of this gene in hemimetabolous insect epithelia remains unknown. To examine the function of Grh signaling in regulating epithelium development in Hemimetabola, we focused on theBlattella germanicaepidermal layer using a gene knockdown strategy. The spatiotemporal expression pattern ofBgGrhwas detected, and knockdown ofBgGrhandBgCad96ca, which provide positive feedback toBgGrh, caused severe defects in new epithelium development and impeded the molting process required to discard the old integument. Knockdown of the expression ofBgGrhandBgCad96cacaused increased expression of chitin synthase gene (BgCHS1) and chitinase gene (BgCht5), the upregulations of which should be mediated by the higher level of hormone receptor 3 (BgHr3) gene. In conclusion, epithelium development is regulated by Grh signaling, which might represent a potential target for the control of urban pest cockroaches.

摘要: When the integrity of airway epithelium is destroyed, the ordered airway barrier no longer exists and increases sensitivity to viral infections and allergens, leading to the occurrence of airway inflammation such as asthma. Here, we found thatgalectin-7transgenic(+) mice exhibited abnormal airway structures as embryos and after birth. These abnormalities included absent or substantially reduced pseudostratified columnar ciliated epithelium and increased monolayer cells with irregular arrangement and widening of intercellular spaces. Moreover, airway tissue fromgalectin-7transgenic(+) mice showed evidence of impaired cell-cell junctions and decreased expression of zonula occludens-1(ZO-1) and E-cadherin. When treated with respiratory syncytial virus (RSV) or ovalbumin (OVA),galectin-7transgenic(+) mice developed substantially increased bronchial epithelial detachment and apoptosis, airway smooth muscle and basement membrane thickening, and enhanced airway responsiveness. We found that Galectin-7 localized in the cytoplasm and nucleus of bronchial epithelial cells, and that increased apoptosis was mediated through mitochondrial release of cytochrome c and upregulated JNK1 activation and expression of caspase-3 ingalectin-7Tg(+) mice. These findings suggested that Galectin-7 causes airway structural defects and destroys airway epithelium barrier, which predispose the airways to RSV or OVA-induced epithelial apoptosis, injury, and other asthma responses.