Delineating the genetic regulation of cannabinoid biosynthesis during female flower development in Cannabis sativa

O_LICannabinoids are predominantly produced in the glandular trichomes on cannabis female flowers. There is little known on how cannabinoid biosynthesis is regulated during female flower development. We aim to understand the rate-limiting step(s) in the cannabinoid biosynthetic pathway. C_LIO_LIWe investigated the transcript levels of cannabinoid biosynthetic genes as well as cannabinoid contents during 7 weeks of female flower development. We demonstrated that the enzymatic steps for producing CBG, which involve genes GPPS, PT and OAC, could be rate limit cannabinoid biosynthesis. Our findings further suggest that cannabinoid synthases, CBDAS and THCAS in a hemp and medical marijuana variety respectively, are not critical for cannabinoid biosynthesis. The cannabinoid biosynthetic genes are generally upregulated during flower maturation, which indicate glandular trichome development. C_LIO_LIMeJA can potentially increase cannabinoid production. We propose that biweekly application of 100 M MeJA staring from flower initiation would be efficacious for promoting cannabinoid biosynthesis. C_LIO_LIOur findings suggest that the step of CBG production could rate limit the terminal cannabinoid biosynthesis. In addition, different cannabis varieties demonstrated discrete transcriptional regulation of cannabinoid biosynthetic genes. C_LI