Genomic description of critical cannabinoid biosynthesis genes

Cannabinoid production is a key attribute of the plant Cannabis sativa and characterizing the genes involved is an essential first step to develop tools for their optimization. We used bioinformatic approaches to annotate and explore variation in the genes coding for enzymes comprising the cannabinoid pathway: olivetol synthase (OLS), olivetolic acid cyclase (OAC), cannabigerolic acid synthase (CBGAS), and the cannabinoid oxidocyclases (THCAS, CBDAS, CBCAS) in multiple C. sativa genome assemblies from diverse lineages. The former three enzymes generate the precursor molecules for the oxidocyclases to produce cannabinoids THC and CBD. We show that duplications of OLS and OAC are consistent across varieties, and that OAC has the least amount of sequence diversity based on phylogenetic comparisons. We also found that one CBGAS-like gene exhibits copy number variation among varieties. We discuss implications of these genes existing on separate chromosomes (with homologs of each found in close proximity), and the significance of CBGAS being located on the X chromosome for cannabinoid production in female plants. This study provides valuable insight on the genomic identity and variation of cannabinoid biosynthesis genes that will benefit future research on the origin and evolution of this pathway, a driver of economic, social, and medicinal value.