Evolution, Expansion and Characterization of Cannabinoid Synthase Gene Family in Cannabis Sativa

Abstract

We are working toward a complete functional and genomic characterization of the cannabinoid synthase family in Cannabis (itself part of the larger Berberine Bridge Enzyme family). This clade, which is unique to Cannabis, includes four main subclades that appear to have arisen by a series of gene duplications. We have functionally characterized three cannabinoid synthases, in addition to the three already characterized, so that now all four subclades contain at least one characterized enzyme. The previously uncharacterized Clade C enzymes have relatively low activity and produce CBCA as their primary product. In addition, we report genomic characterization to better understand the structure and high level of copy number variation in this family. We report a pattern of shared regions immediately upstream of the cannabinoid synthase genes that suggests a specific sequence of breakpoints, and hence gene duplication events. We present a model of gene family expansion to account for the observed data, along with evidence that this expansion occurred under selective pressure. This work adds to our understanding of both the high level of variability in this family and the origin of THCA in type III plants lacking a functional THCAS gene.