Termite soldier mandibles are elongated by dachshund under hormonal and Hox gene controls

• DOI: 10.1242/dev.171942
• Publication Date: 2019-03-04T22:19:43Z
• Authors: Yasuhiro Sugime; Kohei Oguchi; Hiroki Gotoh; Yoshinobu Hayashi; Masatoshi Matsunami; Shuji Shigenobu; Shigeyuki Koshikawa; Toru Miura
• Keywords: Homeodomain Proteins; 0301 basic medicine; Behavior, Animal; Gene Expression Profiling; Genes, Homeobox; Gene Expression Regulation, Developmental; Nuclear Proteins; Epistasis, Genetic; Isoptera; Mandible; Molting; Juvenile Hormones; 03 medical and health sciences; Morphogenesis; Animals; Insect Proteins; Insulin; RNA Interference; Body Patterning; Signal Transduction

ABSTRACT In social insects, interactions among colony members trigger caste differentiation with morphological modifications. In termite soldier differentiation, the mandible size considerably increases through two moltings (via the presoldier stage) under the control of juvenile hormone (JH). Regulatory genes are predicted to provide patterning information that induces the mandible-specific cell proliferation. To identify factors responsible for the mandibular enlargement, expression analyses of 18 candidate genes were carried out in the termite Hodotermopsis sjostedti. Among those, dachshund (dac), which identifies the intermediate domain along the proximodistal appendage axis, showed mandible-specific upregulation prior to the molt into presoldiers, which can explain the pattern of cell proliferation for the mandibular elongation. Knockdown of dac by RNAi reduced the mandibular length and distorted its morphology. Furthermore, the epistatic relationships among Methoprene tolerant, Insulin receptor, Deformed (Dfd) and dac were revealed by combined RNAi and qRT-PCR analyses, suggesting that dac is regulated by Dfd, downstream of the JH and insulin signaling pathways. Thus, caste-specific morphogenesis is controlled by interactions between the factors that provide spatial information and physiological status.