Mutagenesis of Odorant Receptor Coreceptor Orco Reveals the Odorant-Detected Behavior of the Predator Eupeodes corollae.

The successful mating of the hoverfly and the search for prey aphids are of great significance for biological control and are usually mediated by chemical cues. The odorant receptor co-receptor (Orco) genes play a crucial role in the process of insect odor perception. However, the function of Orco in the mating and prey-seeking behaviors of the hoverfly remains relatively unexplored. In this study, we characterized the Orco gene from the hoverfly, Eupeodes corollae, a natural enemy insect. We used the CRISPR/Cas9 technique to knock out the Orco gene of E. corollae, and the EcorOrco-/- homozygous mutant was verified by the genotype analysis. Fluorescence in situ hybridization showed that the antennal ORN of EcorOrco-/- mutant lack Orco staining. Electroantennogram (EAG) results showed that the adult mutant almost lost the electrophysiological response to 15 odorants from three types. The two-way choice assay and the glass Y-tube olfactometer indicated that both the larvae and adults of hoverflies lost their behavioral preference to the aphid alarm pheromone (E)-ß-farnesene (EBF). In addition, the mating assay results showed a significant decrease in the mating rate of males following the knock out of the EcorOrco gene. Although the mating of females was not affected, the amount of eggs being laid and the hatching rate of the eggs were significantly reduced. These results indicated that the EcorOrco gene was not only involved in the detection of semiochemicals in hoverflies but also plays a pivotal role in the development of eggs. In conclusion, our results expand the comprehension of the chemoreceptive mechanisms in the hoverflies and offers valuable insights for the advancement of more sophisticated pest management strategies.

Conserved Odorant Receptor, EcorOR4, Mediates Attraction of Mated Female Eupeodes corollae to 1-Octen-3-ol.

Odorant receptors (ORs) in insects are crucial for the detection of chemical signals. However, the functions of the conserved OR genes among insect species are rarely studied. In this study, we analyzed a well-conserved OR clade in Diptera insects and cloned a gene from this clade, EcorOR4, in the hoverfly Eupeodes corollae. Real-time quantitative PCR showed that EcorOR4 was highly expressed in the antennae and upregulated in the mated females, and in vitro functional characterization showed that EcorOR4 was narrowly tuned to 1-octen-3-ol. Electroantennogram assays revealed that the antennal response of mated females to 1-octen-3-ol was significantly higher than that of mated males, but no significant differences were observed between male and female virgins. Finally, a Y-tube olfactometer bioassay showed that 1-octen-3-ol is an attractant for only mated female E. corollae adults. These results demonstrate that EcorOR4 is involved in the detection of 1-octen-3-ol and that this compound may affect the host-finding and oviposition behavior in female E. corollae.

Aromatic Volatiles and Odorant Receptor 25 Mediate Attraction of Eupeodes corollae to Flowers.

Flowering plants attract pollinators with volatile chemicals that include aromatic compounds. Syrphid flies are the largest group of flower visitors in Diptera, but little is known about how they detect floral scents at the molecular level. Here, electroantennogram (EAG) recordings from the antennae of Eupeodes corollae were used to measure responses from 14 aromatic compounds. To identify odorant receptors (ORs) of E. corollae tuned to aromatic volatiles, we analyzed functional profiles of Drosophila melanogaster odorant receptors (ORs), DmelOR46a and DmelOR71a, which are narrowly tuned to phenolic compounds and represent the orthologues of E. corollae OR25 and OR28, respectively. The two genes that are expressed in the antennae of both sexes were functionally characterized. EcorOR25 is narrowly tuned to several structurally related floral scent volatiles, including eugenol, p-cresol, and methyl eugenol. Finally, choice behavior assays showed that eugenol and methyl eugenol were attractants for both sexes of E. corollae adults. This study identified the odorant receptors used by E. corollae to detect aromatic volatiles, suggesting environmentally friendly strategies to attract these beneficial insects.

Neuropilin-1 in human colon cancer: expression, regulation, and role in induction of angiogenesis.

Neuropilin-1 (NRP-1), a recently identified co-receptor for vascular endothelial growth factor, is expressed by several nongastrointestinal tumor types and enhances prostate cancer angiogenesis and growth in preclinical models. We investigated the expression and regulation of NRP-1 and the effect of NRP-1 overexpression on angiogenesis and growth of human colon adenocarcinoma by immunohistochemistry and in situ hybridization. NRP-1 was expressed in 20 of 20 human colon adenocarcinoma specimens but not in the adjacent nonmalignant colonic mucosa. By reverse transcriptase-polymerase chain reaction analysis, NRP-1 mRNA was expressed in seven of seven colon adenocarcinoma cell lines. Subcutaneous xenografts of stably transfected KM12SM/LM2 human colon cancer cells overexpressing NRP-1 led to increased tumor growth and angiogenesis in nude mice. In in vitro assays, conditioned medium from NRP-1-transfected cell lines led to an increase in endothelial cell migration, but did not affect endothelial cell growth. Epidermal growth factor (EGF) led to induction of NRP-1 in human colon adenocarcinoma cells and selective blockade of the epidermal growth factor receptor (EGFR) decreased constitutive and EGF-induced NRP-1 expression. Blockade of the Erk 1/2 and P38 mitogen-activated protein kinase signaling pathways also led to a decrease in constitutive and EGF-induced NRP-1 expression. These findings demonstrate the ubiquitous expression of NRP-1 in human colon cancer and suggest that NRP-1 may contribute to colon cancer angiogenesis and growth. This study also suggests that EGF and mitogen-activated protein kinase signaling pathways play an important role in NRP-1 regulation in colon cancer cells.

Expression and regulation of the novel vascular endothelial growth factor receptor neuropilin-1 by epidermal growth factor in human pancreatic carcinoma.

BACKGROUND: It was recently shown that neuropilin-1 (NRP-1), which was described originally as a receptor for the semaphorins/collapsins (ligands involved in neuronal guidance), is a coreceptor for vascular endothelial growth factor (VEGF) and increases the affinity of specific isoforms of VEGF to its receptor, VEGF-R2. METHODS: The authors investigated the expression and regulation of NRP-1 in human pancreatic adenocarcinoma specimens and cell lines. RESULTS: Immunohistochemical analysis revealed that NRP-1 was expressed in 12 of 12 human pancreatic adenocarcinoma specimens but was absent in nonmalignant pancreatic tissue. Northern blot analysis revealed NRP-1 mRNA expression in 8 of 11 human pancreatic adenocarcinoma cell lines. NRP-1 mRNA expression was increased by epidermal growth factor (EGF) but not by tumor necrosis factor alpha in several of the human pancreatic adenocarcinoma cell lines studied. Treating human Panc-48 adenocarcinoma cells with EGF activated Akt and Erk but not P-38. Blockade of the phosphatidylinositol-3 kinase (PI-3K)/Akt, mitogen-activated protein kinase (MAPK)/Erk, or P-38 pathways abrogated EGF-induced NRP-1 expression. Finally, EGF receptor blockade in vivo led to a decrease in NRP-1 expression in an orthotopic model of human pancreatic carcinoma. CONCLUSIONS: NRP-1 is expressed in most human pancreatic adenocarcinomas and cell lines but not in nonmalignant pancreatic tissue. EGF regulates NRP-1 expression through the PI-3K/Akt and MAPK/Erk signaling pathways, and blockade of the EGF receptor is associated with decreased expression of NRP-1 in vivo. NRP-1 may act as a coreceptor for VEGF in pancreatic carcinoma, as it does in other tumor systems, thereby enhancing angiogenesis and the effect of VEGF on the growth of pancreatic adenocarcinoma.