Cannabis sativa (Cannabis) is a multi-purpose dioecious crop from the Cannabaceae family grown for fibre, seed and pharmaceutical products. The ratio of male and female plants is arguably the largest determinant of dioecious crop yield, making sex expression an economically important trait for Cannabis industries. While male plants produce higher quality fibre, a much higher proportion of females to males is desired in seed production. For medicinal purposes only females are cultivated, as cannabinoid rich trichomes are largely restricted to female flower tissues. Despite sex being determined by an XX/XY chromosomal system, Cannabis is able to undergo chemically induced sex reversion, allowing for the induction and full development of flowers of the opposite sex.
This study explored the regulation of female flower formation by exploiting Cannabis’s capacity for sex reversion through ethylene signalling pathways. By treating XY male plants with the ethylene donor ethephon to induce female flowers. Comparative transcriptome analysis was used to identify genes relating to Ethephon-mediated sex reversion and floral development. A particular focus was given to ABC floral homeotic genes to aid a greater understanding of female sex expression in Cannabis. In addition we were interested whether female flowers on XY male plants would exhibit trichome phenotypes comparable to true female flowers. Cannabinoid and terpene profiles as well as trichome morphology, were compared to explore potential relationships between the expression of homeotic genes, trichome formation and secondary metabolite biosynthesis.