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- Title
Soldier Morphogenesis in the Damp-Wood Termite Is Regulated by the Insulin Signaling Pathway.
- Authors
HATTORI, AKIKO; SUGIME, YASUHIRO; SASA, CHIFUNE; MIYAKAWA, HITOSHI; ISHIKAWA, YUKI; MIYAZAKI, SATOSHI; OKADA, YASUKAZU; CORNETTE, RICHARD; LAVINE, LAURA CORLEY; EMLEN, DOUGLAS J.; KOSHIKAWA, SHIGEYUKI; MIURA, TORU
- Abstract
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 (HsjlnR), PKB/Akt (HsjPKB/ Akt), and FOXO (HsjFOXO) suggest that HsjlnR and HsjPKB/Akt were up-regulated in the period of elongation of mandibles during soldier development. In situ hybridization showed that HsjlnR was strongly expressed in the mandibular epithelial tissues, and RNA interference (RNAi) for HsjlnR 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 I IS 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.
- Subjects
TERMITES; INSECT morphogenesis; MORPHOGENESIS; MORPHOLOGY; EMBRYOLOGY
- Publication
Journal of Experimental Zoology Part B: Molecular & Developmental Evolution, 2013, Vol 320B, Issue 5, p295
- ISSN
1552-5007
- Publication type
Article
- DOI
10.1002/jez.b.22501