Characterisation of GST genes from the Chinese white pine beetle Dendroctonus armandi (Curculionidae: Scolytinae) and their response to host chemical defence.

Abstract

Bark beetles rely on their detoxifying enzymes to resist the defensive terpenoids of host trees. Glutathione S-transferases (GSTs) conjugate xenobiotic compounds with a glutathione moiety (GSH) and often work in tandem with cytochromes P450 or other enzymes that aid in the detoxification, sequestration or excretion of toxic compounds. We identified nine new GST genes in the Chinese white pine beetle (Dendroctonus armandi) and carried out a bioinformatics analysis on the deduced full-length amino acid sequences. These genes belong to four different classes (epsilon, sigma, omega and theta). Differential transcript levels of each class of GST genes were observed between sexes, and, within these levels, significant differences were found among the different adult substages that were fed phloem of Pinus armandi and exposed to six stimuli [(±)-α-pinene, (-)-α-pinene, (-)-β-pinene, (+)-3-carene, (±)-limonene and turpentine] at 8 and 24 h. The increased transcription levels of GST genes suggested that they have some relationship with the detoxification of terpenoids that are released by host trees. The mediating oxidative stress that is caused by monoterpene might be the main role of the bark beetle GSTs.