The role of the deviate gene in foraging behavior and response to environmental conditions in the eastern subterranean termite, Reticulitermes flavipes (Kollar)

Margaret A Schwinghammer, Purdue University

Abstract

The Reticulitermes flavipes deviate gene was investigated to determine its role in termites' response to environmental changes, as well as its effect on important termite behaviors such as trail following and foraging. The deviate gene was expressed in all four termite body regions that were sampled (antennae, head, thorax, and abdomen), and the gene was also present in the three phenotypes sampled (worker, solder, and nymph). To examine the effect of photoperiod on deviate expression, termites were held in either light, dark, or light/dark cycle conditions. These differences in light conditions resulted in altered deviate expression between light and dark treatments, suggesting a possible connection between the deviate gene and termite circadian rhythm. Temperature did not appear to alter deviate expression across the range tested (17°C–27°C), however when juvenile hormone was added to identical temperature treatments, a difference in gene expression was observed between 17°C and 22°C. This information may suggest that the deviate gene is suppressed by juvenile hormone, and that deviate may play a role in the processes associated with caste maintenance and differentiation in termites. Additionally, when RNA-interference (RNAi) was used to silence deviate gene expression, deviate silenced worker termites held in dishes containing a food source treated with juvenile hormone III did not show significant differences from controls in the number presoldiers that developed or the timing of presoldier development. These findings may further support the hypothesis that deviate expression in termites decreases as juvenile hormone increases. Finally, RNAi gene silencing was used to examine the behavioral role of the deviate gene. First a time-course for the RNAi silencing process was developed using quantitative real-time PCR. It was determined that injections with a short-interfering RNA (siRNA) concentration of 1 ng/0.0036 μl resulted in deviate gene silencing to 53.6% of pre-injection levels 24 hours after injection. Deviate expression returned to full pre-injection levels 48 hours after injection. When termites were injected with deviate silencing siRNA and placed in an arena which required them to move 1 meter to find food, the time these termites required to locate the new food source was not significantly different from controls. However, termites showed reduced trail following accuracy 24, 48, and 72 hours after deviate silencing RNAi injections. These results suggest that while deviate expression may not alter the ability of termites to move, it plays a role in trail following accuracy and the ability to detect trails. These studies have provided insight into the biological and behavioral role of the deviate gene in Reticulitermes flavipes , and constructed ideas for future research to further elucidate the role of this gene in termites.

Degree

Ph.D.

Advisors

Bennett, Purdue University.

Subject Area

Entomology

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