A role of JH-Met signaling activity during soldier differentiation in the termite Zootermopsis nevadensis
Yudai Masuoka, Yudai Masuoka , Kiyoto Maekawa
Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, Tsukuba, Japan; Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, Tsukuba, Japan ; Graduate School of Science and Engineering, University of Toyama, Toyama, Japan
In termites, soldier caste is regarded as the first acquired sterile caste. Juvenile hormone (JH) is the central factor for soldier differentiation, and artificial JH treatment of workers can induce presoldier differentiation in many species. Previous study showed that knockdown of JH receptor gene (methoprene tolerant; Met) inhibited soldier differentiation under the JH treatment. Therefore, we expected that the acquisition of novel sensibility against JH-Met signaling response might be required for the soldier formation during the course of termite evolution within the cockroach clade. To test this hypothesis, we investigated the expression and function of genes with JH-Met dependent activity during soldier differentiation in the damp-wood termite Zootermopsis nevadensis. First, we focused on the molting hormone (20-hydroxyecdysone; 20E) synthesis and signaling genes, because two molting processes are definitely necessary for soldier differentiation. We performed knockdown with Met RNAi under the JH analog treatment, and observed gene expression changes. Expression levels of several genes were decreased by Met RNAi. Interestingly, knockdown of these genes with JH-Met dependent activity inhibited not only the presoldier molt, but also the presoldier-specific morphogenesis (e.g. mandibular elongation). Next, to clarify the black box between JH-Met and 20E signalings, transcriptome analysis was performed. We detected some candidate genes involved in soldier differentiation under the JH-Met signaling. Based on the functional analysis of candidate genes, we will discuss about a role of the novel JH signaling for the acquisition of soldiers in termites.