Transcriptomic analysis of ethephon-induced sex reversion of male Cannabis sativa reveals changes in expression of floral homeotic genes and a distinct trichome morphology

Abstract

Cannabis sativa is a dioecious crop whose agricultural productivity is linked to its sex expression. In a medicinal context, only female flowers produce an abundance of glandular trichomes responsible for producing valuable cannabinoids. Thus, understanding sex-determining factors is vital in C. sativa crop improvement for specific end uses. Although an X/Y sex chromosome system determines sex, manipulating ethylene pathways can alter sex expression. We used comparative RNA-seq and metabolite analysis on floral tissue to explore the regulation of male-to-female sex reversion and changes in secondary metabolite production induced by the ethylene donor ethephon. Differentially expressed gene analysis revealed significant alterations in class B and E floral homeotic gene homologue expression early in the flowering phase, which pointed to their direct role in forming unisexual flowers in cannabis. Metabolite analysis indicated a higher proportion of sesquiterpenes and cannabichromenic acid in induced female flowers compared with non-induced female flowers. Combined with a morphological comparison of trichomes, the secondary metabolite profiles indicated a preferential development of sessile trichomes via up-regulation of a GLABRA1 homologue. This study enhances our understanding of ethylene-driven sex regulation and its link to secondary metabolite accumulation in C. sativa.