Establishment of tools for neurogenetic analysis of sexual behavior in the silkmoth, Bombyx mori.
BACKGROUND
Silkmoth, Bombyx mori, is an ideal model insect for investigating the neural mechanisms underlying sex pheromone-induced innate behavior. Although transgenic techniques and the GAL4/UAS system are well established in the silkmoth, genetic tools useful for investigating brain function at the neural circuit level have been lacking.


RESULTS
In the present study, we established silkmoth strains in which we could visualize neural projections (UAS-mCD8GFP) and cell nucleus positions (UAS-GFP.nls), and manipulate neural excitability by thermal stimulation (UAS-dTrpA1). In these strains, neural projections and nucleus position were reliably labeled with green fluorescent protein in a GAL4-dependent manner. Further, the behavior of silkworm larvae and adults could be controlled by GAL4-dependent misexpression of dTrpA1. Ubiquitous dTrpA1 misexpression led both silkmoth larvae and adults to exhibit seizure-like phenotypes in a heat stimulation-dependent manner. Furthermore, dTrpA1 misexpression in the sex pheromone receptor neurons of male silkmoths allowed us to control male sexual behavior by changing the temperature. Thermally stimulated male silkmoths exhibited full sexual behavior, including wing-flapping, orientation, and attempted copulation, and precisely approached a thermal source in a manner similar to male silkmoths stimulated with the sex pheromone.


CONCLUSIONS
These findings indicate that a thermogenetic approach using dTrpA1 is feasible in Lepidopteran insects and thermogenetic analysis of innate behavior is applicable in the silkmoth. These tools are essential for elucidating the relationships between neural circuits and function using neurogenetic methods.
Division of Life Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Ishikawa, Japan.
Taketoshi
T
Kiya
Division of Life Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Ishikawa, Japan.
Koudai
K
Morishita
Transgenic Silkworm Research Unit, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan.
Keiro
K
Uchino
Division of Life Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Ishikawa, Japan.
Masafumi
M
Iwami
Transgenic Silkworm Research Unit, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan.
Hideki
H
Sezutsu
D000818:Animals; D030801:Animals, Genetically Modified / Q000235:genetics / Q000502:physiology; D012831:Bombyx / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D004625:Embryo, Nonmammalian / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D007814:Larva / Q000378:metabolism; D008297:Male; D023421:Models, Animal; D009474:Neurons / Q000378:metabolism; D012725:Sexual Behavior / Q000502:physiology*; D013696:Temperature; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D050051:Transient Receptor Potential Channels / Q000235:genetics / Q000378:metabolism
D014157:Transcription Factors; D050051:Transient Receptor Potential Channels; D049452:Green Fluorescent Proteins