| Bark beetles oxidize the defensive allelochemicals from their host trees to both detoxify and convertthese materials into components of their pheromone system. The ability of this insect to adapt to itschemical environment might be explained by the action of major detoxification enzymes such as cytochrome P450s(or CYPs). It is only now becoming evident that the number and range of P450 s with in an individual organism reflect, to some extent, its lifestyleand defense mode against environmental toxins. The constitutive and induced defensive system of the host pine, which consists of a multitude of monoterpenes, sesquiterpenes andditerpenes, can stop or delay the entrance ofpioneer beetles into the tree and inhibit the attractiveness of thetree to flying beetles. Therefore, we focus on the Chinese white pinebeetle(Dendroctonus armandi) P450 genes expression and their detoxification. Leptographium qinlingensis as a fungal associate of the Chinese white pine beetle is cooperate with the beetles to invade the host.Our study includes these aspects: research the P450 genes’ expression profiles in different stages and tissues; test the tolerance of D. armandifor Pinus armandi volatile substrates and the response of P450 genes transcription levels for host allelochemicals; discover their diversity in functions andfund out the key P450 genes for overcome the host allelochemicals.And we also identify P450 genes of L. qinlingensis, and their expression levels under the terpenoids treatment.The mainly results are as follows:1. The tolerance of D. armandi adults for 5 monoterpenes:(±)-α-Pinene,(-)-α-Pinene,(-)-β-Pinene,(+)-3-Carene,(±)-Limonene and turpentine are significant different. The host terpenoids can kill the beetles when their concentration up to 600 ppm.2. The Chinese white pine beetle has 64 P450 genes at least, and some beetles’ specific P450 genes occur in CYP3 clade. Their functions might be related with the adaption for their special habitats and their behavior.3. Forty-three P450 genes’ expression profiles in D. armandi different development stages suggest their function diversity. Many P450 genes expression are up-regulate in other stages relative to larvae. Some P450 genes expression levels from every clades have a grate change in pupae, suggest that multiple P450 enzymes take part in the translation from larvae to adults. The expression levels ofP450 genes from CYP3 and CYP4 clades changes significantly after the invasion, suggest a role in host selection and detoxification.4. The tissue specificity of these P450 genes wasdetermined in three tissues(antenna, gut and reproductive organs).The P450 genes special expressed in gut are related with reduce the toxic of the host resin, and P450 genes special expressed in antenna could be acted as the odor molecules degradation enzyme.5. The differential transcript accumulation patterns of CYP genes of the bark beetle providedinsight into the ecological interactions of D. armandi with its host pine.The transcription level of CYP genes from L. qinlingensis following treatment with terpenes and pine phloem extracts was upregulated, and indicates the association of beetles and fungus for invade the host.6. We have identified an L. qinlingensis CYP51F1 gene which has the typical protein active site and membrane anchor structure domain of 14-α-demethylase. Molecular docking speculates the degration of P. armandi terpenoids(sterols) by the CYP51F1, and indicates the association of beetles and fungus in overcome the host defanse. |
PDF Full Text Request