title: Knockdown of the juvenile hormone receptor gene inhibits soldier-specific morphogenesis in the damp-wood termite Zootermopsis nevadensis (Isoptera: Archotermopsidae).
abstract: The Methoprene-tolerant (Met) protein has been established as a juvenile hormone (JH) receptor. Knockdown of the Met gene caused precocious metamorphosis and suppression of ovarian development. However, the function of Met in caste development of social insects is unclear. In termites, JH acts as a central factor for caste development, especially for soldier differentiation, which involves two molts from workers via a presoldier stage. Increased JH titer in workers is needed for the presoldier molt, and the high JH titer is maintained throughout the presoldier period. Although presoldiers have the fundamental morphological features of soldiers, the nature of the cuticle is completely different from that of soldiers. We expected that JH signals via Met are involved in soldier-specific morphogenesis of the head and mandibles during soldier differentiation, especially in the presoldier period, in natural conditions. To test this hypothesis, we focused on soldier differentiation in an incipient colony of the damp-wood termite Zootermopsis nevadensis. Met homolog (ZnMet) expression in heads increased just after the presoldier molt. This high expression was reduced by ZnMet double stranded (dsRNA) injection before the presoldier molt. Although this treatment did not cause any morphological changes in presoldiers, it caused strong effects on soldiers, their mandibles being significantly shorter and head capsules smaller than those of control soldiers. Injection of ZnMet dsRNA throughout the presoldier stage did not affect the formation of soldier morphology, including cuticle formation. These results suggested that the rapid increase in ZnMet expression and subsequent activation of JH signaling just after the presoldier molt are needed for the formation of soldier-specific weapons. Therefore, besides its established role in insect metamorphosis, the JH receptor signaling also underlies soldier development in termites.
authors.affiliation: Graduate School of Science and Engineering, University of Toyama, Toyama, Japan.
authors.forename: Yudai
authors.initials: Y
authors.lastname: Masuoka
authors.affiliation: Graduate School of Science and Engineering, University of Toyama, Toyama, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Yaguchi
authors.affiliation: Graduate School of Science and Engineering, University of Toyama, Toyama, Japan.
authors.forename: Ryutaro
authors.initials: R
authors.lastname: Suzuki
authors.affiliation: Graduate School of Science and Engineering, University of Toyama, Toyama, Japan.
authors.forename: Kiyoto
authors.initials: K
authors.lastname: Maekawa
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D055785:Gene Knockdown Techniques; D006257:Head / Q000254:growth & development; D020049:Isoptera / Q000235:genetics* / Q000254:growth & development*; D007605:Juvenile Hormones / Q000235:genetics / Q000378:metabolism*; D008334:Mandible / Q000254:growth & development / Q000378:metabolism; D018978:Molting; D009024:Morphogenesis; D012330:RNA, Double-Stranded / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D007605:Juvenile Hormones; D012330:RNA, Double-Stranded
keywords: Juvenile hormone; Methoprene-tolerant; Soldier differentiation; Termites