Exploring the Molecular Mechanisms of Glandular Trichome Development and Cannabinoid Biosynthesis in Cannabis sativa

Cannabinoids are a group of commercially valuable compounds, such as cannabidiolic acid, cannbigerolic acid et al, made primarily in cannabis female flower trichomes. Therefore, Cannabis sativa would be a great model plant to study glandular trichome initiation and development. There is no published study up to now on trichome development in cannabis at the molecular level, and no genes responsible for trichome initiation have been characterized. Our lab is mainly interested in the molecular mechanisms of glandular trichome development and the regulation of genes involved in cannabinoid biosynthesis. We have identified transcription factors (TFs) that could potentially regulate glandular trichome initiation and genes for cannabinoid biosynthesis. Our preliminary results have shown that the expression of two of the TFs increases with the maturity of flowers, which also coordinates the development of trichomes as the flower matures. The expression of the two TFs also correlates with the production of cannabinoids, indicating that they are playing important roles in trichome development. Our work on the cannabinoid biosynthesis genes showed a similar expression pattern, indicating that trichome development is critical for cannabinoid production. Responsive elements that may be regulated by plant hormones jasmonic acid or salicylic acid are also found in the promoter regions of cannabinoid biosynthetic genes. We further identified several TFs, including genes from the MYB and WRKY families, using trichome RNAseq datasets. Both MYB and WRKY family members have been shown to regulate genes involved in secondary metabolite biosynthesis. Promoter analysis of the genes showed binding sites of either MYB or WRKY TFs, suggesting the regulation of these genes by the TFs. Our findings will advance the understanding of cannabinoid biosynthesis and provide insights on the improvement of cannabinoid production.