A specialized ABC efflux transporter G c ABC ‐ G 1 confers monoterpene resistance to G rosmannia clavigera , a bark beetle‐associated fungal pathogen of pine trees

SummaryG rosmannia clavigera is a bark beetle‐vectored pine pathogen in the mountain pine beetle epidemic in western N orth A merica. G rosmannia clavigera colonizes pines despite the trees' massive oleoresin terpenoid defences. We are using a functional genomics approach to identify G . clavigera 's mechanisms of adaptation to pine defences. We annotated the ABC transporters in the G . clavigera genome and generated RNA ‐seq transcriptomes from G . clavigera grown with a range of terpenes. We functionally characterized GcABC‐G1 , a pleiotropic drug resistance ( PDR ) transporter that was highly induced by terpenes, using qRT‐PCR, gene knock‐out and heterologous expression in yeast. Deleting GcABC‐G1 increased G . clavigera 's sensitivity to monoterpenes and delayed development of symptoms in inoculated young lodgepole pine trees. Heterologous expression of GcABC‐G1 in yeast increased tolerance to monoterpenes. G . clavigera but not the deletion mutant, can use (+)‐limonene as a carbon source. Phylogenetic analysis placed GcABC‐G1 outside the ascomycete PDR transporter clades. G . clavigera appears to have evolved two mechanisms to survive and grow when exposed to monoterpenes: GcABC‐G1 controls monoterpene levels within the fungal cells and G. clavigera uses monoterpenes as a carbon source. This work has implications for understanding adaptation to host defences in an important forest insect–fungal system, and potentially for metabolic engineering of terpenoid production in yeast.