Enhanced locomotor behavior is mediated by activation of tyrosine hydroxylase in the silkworm brain.

Animal behavior regulation is a complex process involving many factors, and the nervous system are essential factor in this process. In many species, pathogens can alter host behavior by affecting the host's nervous system. An interesting example is the silkworm shows an enhanced locomotor behavior after infected with the nucleopolyhedrosis virus. In this study, we analyzed the transcriptome of silkworm brain at different time points after infection and found that various genes related to behavior regulation changed after infection. In-depth analysis showed that the tyrosine hydroxylase gene might be a key candidate gene, and the content of dopamine, its downstream metabolite, increased significantly in the brain of silkworm infected with the virus. After injection of tyrosine hydroxylase inhibitor into the infected silkworm, the dopamine content in the silkworm brain decreased and the locomotor behavior caused by the virus was blocked successfully. These results confirm that tyrosine hydroxylase is involved in regulating enhanced locomotor behavior after virus infection in silkworm. Furthermore, the tyrosine hydroxylase gene was specifically overexpressed in the brain of silkworm, and the transgenic silkworm was enhanced in locomotor behavior and foraging behavior. These results suggest that the tyrosine hydroxylase gene plays a vital role in regulating insect behavior.