Regulation of secondary metabolism in Cannabis sativa glandular trichomes by abscisic acid and water deficit stress during late flowering development

• Drought increases cannabigerolic acid content in cannabis glandular trichomes. • Drought does not upregulate the cannabinoid biosynthetic pathway. • Increase in specific cannabinoids could be due to reallocation of carbon resources. • Abscisic acid regulates drought response in the glandular trichome indirectly. • Ethylene and salicylic acid are the likely intermediate signalling pathways. Cannabis ( Cannabis sativa L.) is a medicinally important plant of moderate drought tolerance. The glandular trichomes (GT) on female flowers of cannabis are the main site of production and storage of cannabinoids and terpenoids. While water deficit stress (WD) was shown to modulate cannabinoid content in cannabis, it remains unknown how GT regulation is affected to achieve this. We quantified the GT proteome and floral cannabinoid and terpenoid content in late flowering ‘Hindu Kush’ cannabis treated with either short-term WD or with an abscisic acid (ABA) foliar spray. We found that WD and ABA changed the abundance of many of the same proteins in the GT, with changes reflecting a decrease in primary metabolic processes and an increase in stress response mechanisms. Results suggested ABA likely mediates changes in the GT indirectly by affecting salicylic acid and ethylene signalling. WD caused the cannabinoid cannabigerolic acid to increase in content, while ABA caused monoterpene content to increase. Interestingly, proteins involved in the cannabinoid and terpenoid biosynthetic pathways either decreased in abundance or did not change in either treatment, indicating that the increased secondary metabolite content is likely driven by a process other than upregulation of the pathways’ proteins.