title: High juvenile hormone titre and abdominal activation of JH signalling may induce reproduction of termite neotenics.
abstract: Termite castes are a key example of polyphenism, in which reproductive division of labour is clearly seen in colonies. The reproductive castes in termites include primary and neotenic reproductives; primary reproductives found a new colony whereas neotenics succeed them in the reproductive role when the primary reproductives die or become senescent. Neotenics usually differentiate from nymphs or workers by developing functional gonads while retaining juvenile characteristics; however, the developmental mechanism during neotenic differentiation remains poorly understood. Juvenile hormone (JH) mediates a number of aspects of developmental regulation in caste differentiation in termites. In the present study we quantified JH titres in neotenic reproductives of Reticulitermes speratus, and compared these with other developmental stages. In addition, expression changes in JH signalling gene homologues (Methoprene-tolerant [Met], Krüppel-homolog1, Broad-Complex) in the head, thorax and abdomen were investigated during neotenic differentiation. Finally, we examined the function of Met in reproduction of neotenics by RNA interference (RNAi). Our results showed that the JH titres of neotenics were significantly higher than those of nymphs and workers. JH signalling genes were highly expressed in neotenic abdomens, compared with those in workers and nymphs. Met RNAi resulted in the inhibition of vitellogenin gene expression in newly moulted neotenics. These results suggest that the fertility of neotenics might be controlled by a large increase of JH titres and body-part-specific activation of JH signalling pathways.
authors.affiliation: Department of Biology, Graduate School of Science and Engineering, University of Toyama, Toyama, 930-8555, 3190, Gofuku, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Saiki
authors.affiliation: Department of Entomology, Washington State University, Pullman, WA, 99164, USA.|Laboratory of Ecological Genetics, Graduate School of Environmental Science, Hokkaido University, Sapporo, Hokkaido, 060-0810, Japan.|Laboratory of Sericulture and Entomoresources, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, 466-8550, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Gotoh
authors.affiliation: Department of Biology, Graduate School of Science and Engineering, University of Toyama, Toyama, 930-8555, 3190, Gofuku, Japan.|Laboratory of Sericulture and Entomoresources, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, 466-8550, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Toga
authors.affiliation: Laboratory of Ecological Genetics, Graduate School of Environmental Science, Hokkaido University, Sapporo, Hokkaido, 060-0810, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Miura
authors.affiliation: Department of Biology, Graduate School of Science and Engineering, University of Toyama, Toyama, 930-8555, 3190, Gofuku, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Maekawa
mesh_terms: D000818:Animals; D005260:Female; D018507:Gene Expression Regulation, Developmental; D020049:Isoptera / Q000254:growth & development / Q000502:physiology*; D007605:Juvenile Hormones / Q000378:metabolism*; D018978:Molting; D009758:Nymph / Q000502:physiology; D034622:RNA Interference; D012098:Reproduction; D015398:Signal Transduction; D014819:Vitellogenins / Q000096:biosynthesis
chemical_list: D007605:Juvenile Hormones; D014819:Vitellogenins
keywords: caste differentiation; juvenile hormone; neotenic reproductives; termites