Meeting Abstract
Although herbivory is a common strategy in mammals, few species display dietary specialization likely because of limitations in metabolizing high levels of similar plant secondary compounds in a single plant species. To advance our understanding of dietary specialization, we investigated aspects of hepatic metabolism in a juniper specialist, Neotoma stephensi (diet >85% Juniperus monosperma), in comparison to a generalist, N. albigula (diet ≤30% juniper). We conducted juniper feeding trials with woodrats and measured the protein content and sequence diversity of a key detoxification enzyme, cytochrome P450 2B (CYP2B). We also measured microsomal turnover of α-pinene, the most abundant terpene in J. monosperma. In both species, addition of 30% juniper to the diet increased CYP2B expression (2.5 fold) and α-pinene turnover rates (4-fold). In the specialist, higher levels of dietary juniper (60%, 85%) further induced CYP2B and increased α-pinene turnover rates. Although no species differences in feeding or α-pinene turnover rates were observed at 30% dietary juniper, CYP2B protein levels were 1.7-fold higher in the specialist relative to the generalist (p<0.01). Similarly, the specialist possessed ~5 more CYP2B gene copies, and despite greater copy number, exhibited less CYP2B sequence diversity. Because the generalist does not consume more than 30% juniper, it is unknown if this species lacks the ability to further increase expression of CYP2B or other enzymes that metabolize α-pinene. However, the increased CYP2B content and α-pinene turnover rates in generalists exposed to 60% or 85% juniper suggest CYP2B enzymes support this species’ ability to specialize on juniper.
