Populus Genome Integrative Explorer (PopGenIE) is an integrated set of tools for exploring the genome and transcriptome of the model plant system Populus. PopGenie is a model organism database (MOD) which brings together the increasingly extensive collection of genetics and genomics data created by the scientific community in a central resource. Such MODs offer a single entry point to the collection of resources available within a model system, typically including tools for exploring and querying those resources. PopGenIE contains an integrated set of tools including genome, synteny and quantitative trait locus (QTL) browsers for exploring genetic data. Expression tools include an electronic fluorescent pictograph (eFP) browser, expression profile plots, co-regulation within collated trans