Dual RNA-Seq Analysis of the Pine- Interaction in Resistant () and Susceptible () Hosts.

poses a serious threat to many pine species in both commercial and natural pine forests. Knowledge regarding the molecular basis of pine- host-pathogen interactions could assist efforts to produce more resistant planting stock. This study aimed to identify molecular responses underlying resistance against . A dual RNA-seq approach was used to investigate host and pathogen expression in challenged (resistant) and (susceptible), at three- and seven-days post inoculation. RNA-seq reads were mapped to combined host-pathogen references for both pine species to identify differentially expressed genes (DEGs). genes expressed during infection showed decreased ergosterol biosynthesis in relative to . For , enriched gene ontologies and DEGs indicated roles for auxin-, ethylene-, jasmonate- and salicylate-mediated phytohormone signalling. Correspondingly, key phytohormone signaling components were down-regulated in . Key ergosterol biosynthesis genes were expressed at lower levels during infection of the resistant relative to the susceptible host. This study further suggests that coordination of phytohormone signaling is required for resistance in , while a comparatively delayed response and impaired phytohormone signaling contributes to susceptibility in .