Molecular and neural plasticity in the pheromone response of the corn earworm moth (Helicoverpa zea)
LE3 .A278 2022
Master of Science
Sexual communication in the moth Helicoverpa zea (corn earworm) depends on males detecting and orienting to sex pheromone blends released by females. Trichoid sensilla on male antennae contain olfactory sensory neurons (OSNs) with olfactory receptors (ORs) which are tuned to specific chemicals in the blends of conspecific and heterospecific females. Pre-exposure of moths to pheromones can cause long-term alterations in OSN sensitivity and mating behaviors, but mechanisms underlying this plasticity are unknown. Some evidence suggests plasticity could be driven by alterations in expression of ORs detecting pheromones, although this claim is debated. My objective was to determine how pre-exposure to sex pheromone components could alter OR gene expression and/or electroantennogram (EAG) sensitivity in H. zea, and if these effects were dependent on exposure time or concentration of stimulus. Isolated, 2-4-day-old moths were exposed to different concentrations of conspecific or heterospecific pheromone components for 1 or 24 hours. Antennae were removed and used for either quantitative PCR to detect differences in OR gene expression or EAGs to measure the sensitivity of OSNs. Alterations in OR gene expression were found in three trials, but patterns of expression were inconsistent. Pre-exposure to 6 mg of Z11-16:Ald in males for 24 hours increased EAG responses to most pheromone components and linalool, while pre-exposure to 6 mg of Z9-16:Ald for 24 hours decreased EAG responses to Z9-16:Ald and linalool in females. No consistent link between OR gene expression and EAG sensitivity was found. This research will provide insight into mechanisms underlying insect olfaction and potentially improve pheromone-based pest control methods.
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