Soldier Morphogenesis in the Damp-Wood Termite Is Regulated by the Insulin Signaling Pathway
Article first published online: 23 MAY 2013
Copyright © 2013 Wiley Periodicals, Inc.
Journal of Experimental Zoology Part B: Molecular and Developmental Evolution
Volume 320, Issue 5, pages 295–306, July 2013
How to Cite
2013. Soldier morphogenesis in the damp-wood termite is regulated by the insulin signaling pathway. J. Exp. Zool. (Mol. Dev. Evol.) 320B:295–306., , , , , , , , , , , .
- Issue published online: 10 JUN 2013
- Article first published online: 23 MAY 2013
- Manuscript Accepted: 2 MAR 2013
- Manuscript Revised: 20 JAN 2013
- Manuscript Received: 13 AUG 2012
- Ministry of Education, Culture, Sports, Science and Technology of Japan. Grant Number: 21677001
- Japan Society for the Promotion of Science
Eusocial insects exhibit various morphological castes associated with the division of labor within a colony. Termite soldiers possess defensive traits including mandibles that are greatly exaggerated and enlarged, as compared to termite reproductives and workers. The enlarged mandibles of soldiers are known to result from dynamic morphogenesis during soldier differentiation that can be induced by juvenile hormone and its analogs. However, the detailed developmental mechanisms still remain unresolved. Because the insulin/insulin-like growth factor signaling (IIS) pathway has been shown to regulate the relative sizes of organs (i.e., allometry) in other insects, we examined the expression profiles of major IIS factors in the damp-wood termite Hodotermopsis sjostedti, during soldier differentiation. The relative expression patterns of orthologs for termite InR (HsjInR), PKB/Akt (HsjPKB/Akt), and FOXO (HsjFOXO) suggest that HsjInR and HsjPKB/Akt were up-regulated in the period of elongation of mandibles during soldier development. In situ hybridization showed that HsjInR was strongly expressed in the mandibular epithelial tissues, and RNA interference (RNAi) for HsjInR disrupted soldier-specific morphogenesis including mandibular elongation. These results suggest that signaling through the IIS pathway is required for soldier-specific morphogenesis. In addition, up-regulation of the IIS pathway in other body tissues occurred at earlier stages of development, indicating that there is tissue-specific IIS regulation. Because the IIS pathway is generally thought to act upstream of JH in insects, our results suggest the damp-wood termite may have evolved a novel feedback loop between JH and IIS that enables social interactions, rather than nutrition, to regulate caste determination. J. Exp. Zool. (Mol. Dev. Evol.) 320B:295–306, 2013. © 2013 Wiley Periodicals, Inc.