Genomic description of critical upstream cannabinoid biosynthesis genes

Cannabinoid production is one of the key attributes of the plant Cannabis sativa and the characterization of 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 coding genes for critical enzymes comprising the cannabinoid pathway: Olivetol Synthase (OLS), Olivetolic Acid Cyclase (OAC), and Cannabigerolic Acid Synthase (CBGAS), in multiple C. sativa genomes. These upstream genes of the Cannabinoid Oxidocyclase Genes THCAS, CBDAS, and CBCAS generate the necessary precursor molecules to produce the cannabinoids THC and CBD. We found that these genes vary in copy number and confirm that OLS, OAC, CBGAS, and the Cannabinoid Oxidocyclases are on separate chromosomes, while homologs are found in proximity. CBGAS, located on Chromosome X, suggests potential dosage effects in female plants. Except for the Cannabinoid Oxidocyclase genes, the other genes have multiple exons, up to 10 in CBGAS. Through differential exon usage explorations in CBGAS we found evidence for potential regulatory differences. 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, driver of economic, social, and medicinal value.