Gene duplication and expression of specialized metabolic pathway genes in Cannabis sativa

Cannabis sativa is now widely cultivated for recreational and medicinal markets (drug-type cannabis) in addition to fiber and grain for materials and foodstuffs (fiber-type cannabis). Cannabis often is grown for its female flowers, which are highly concentrated with the specialized metabolites cannabinoids and terpenes. These compounds are specifically found in glandular trichomes, which are abundant on the surfaces of maturing cannabis flowers. However, both the abundance and identity of specialized metabolites can vary considerably across different cannabis varieties. Drug-type cannabis commonly contains the cannabinoid, THC, and fiber-type cannabis contains CBD. In this research, 24 gene families from the biochemical pathways responsible for cannabinoid and terpenoid production were analyzed across five different genomes of Cannabis sativa, containing a diversity of chemical and physical phenotypes. Orthologous genes from hops and three other Rosales species also were included. Gene duplication patterns and copy number variation were investigated using phylogenetic trees to define the evolutionary patterns within these biochemical pathways. Additionally, the duplicated genes within these pathways were analyzed for gene expression in several organ types of the Purple Kush variety. When comparing the terpenoid and cannabinoid pathways, both the non-mevalonate (MEP) and mevalonate (MVA) pathways contained fewer duplicated genes than the genes involved in cannabinoid biosynthesis. The evolutionary origins of the olivetolic acid cyclase (OAC) and aromatic prenyltransferase (APT) genes were revealed when comparing with hops and other closely related species. The gene expression analysis of the Purple Kush cultivar indicated that genes involved in both terpenoid and cannabinoid pathways were expressed highest in flowers. However, the number of expressed copies and expression levels varied among genes, and different copies are expressed in different organ types. Overall, this thesis provides insights to the evolutionary histories and gene expression patterns of the biochemical pathways involved in cannabinoid and terpenoid biosynthesis of Cannabis sativa.Science, Faculty ofBotany, Department ofGraduat