Submitted to: Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 1, 2011
Publication Date: February 9, 2012
Citation: Tarver, M.R., Florane, C.B., Zhang, D., Grimm, C.C., Lax, A.R. 2012. Methoprene and temperature effects on caste differentiation and protein composition in the formosan termite, Coptotermes formosanus. Insect Science. 12:18. Interpretive Summary: Termites are a major world wide pest, who each year can cause millions of dollars in damages and repair cost to personal property and some crops. Termites are unique because they have multiple castes to perform different roles within the colony. Termite caste differentiation, specifically worker-to-soldier molts, is a complex process whose exact mechanisms are still not known. Our overall goal was to investigate the effect of various temperatures and hormonal treatment on termite caste differentiation and total protein content in the formosan termite (Coptotermes formosanus). Results from these and past experiments indicate that increasing temperature causes and increase in soldier formation. Also a number of proteins fluctuated in response to the different factors. Prominent proteins were further examined to correlate changes in protein levels to temperature, time and exposure to the chemical methoprene, a juvenile hormone analog. Together these results can help better understand the complex process of termite caste differentiation.
Technical Abstract: The utilization of multiple caste is a shared feature of many social insects. In termites, multiple extrinsic factors have been shown to impact caste differentiation; for example, temperature has been shown to increase soldier production. The objective of this investigation was to examine and correlate the effects of temperature variation on termite caste differentiation and identify the resulting changes in protein level. Our results indicate that worker to soldier differentiation is modulated by temperature, where a greater number of soldiers developed at a higher rate, compared to lower temperatures. We analyzed total protein by SDS-PAGE, LC/MS/MS, and N-terminal sequencing and found several changes. Specifically, we identified four proteins, Hexamerin-1, Hexamerin-2, Endo-beta 1,4 glucanase, and myosin. These proteins were further examined for their response to temperature, time, and exposure to the juvenoid hormone analog methoprene. Hexamerin-1 protein showed a temperature and time dependent effect, while hexamerin-2 protein level was affected by temperature and exposure to methoprene. Endo-beta 1, 4 glucanase and myosin were affected by time and exposure to methoprene. Our analysis allows the correlation of temperature, time, and presence of methoprene with specific changes in protein level that occur during caste differentiation. These results can be directly applied to better understand the complex developmental factors that control termite differentiation and guide the use of juvenile hormone analogs to maximize efficiency of termite eradication in the field.