Revisiting sex plasticity in Cannabis sativa L.: A hormonal cross-talk in flower masculinisation

Abstract

Sex determination in Cannabis sativa L. has major implications for breeding, biotechnology, and crop management. In this species, sex is primarily governed by an XX/XY sex chromosome system, with genetic regulation constituting the principal level of control. Variation in sex expression, encompassing dioecious, monoecious, or hermaphroditic forms, may arise from interactions between sex chromosomes and autosomal factors X-to-autosome (X: A) chromosome balance. Secondary modulation of sex phenotype involves environmental and physiological influences, with phytohormonal regulation representing an important layer of sex plasticity. Epigenetic mechanisms may further contribute to the downstream fine-tuning of phenotypic sex expression. Importantly, sex expression in Cannabis can also be manipulated chemically. Several silver-based compounds, such as silver thiosulfate, are widely used to induce staminate flower formation in genetically female plants, whereas application of ethephon promotes female flower formation in genetically male individuals. Although both agents act through ethylene signalling pathway, their effects likely involve broader and more complex interactions within the molecular network, including cross-talk with other hormonal pathways. Within this context, transcriptional regulators associated with auxin signalling, including Aux/IAA – TOPLESS-RELATED co-repressors such as TPR1, may contribute to the activation of male developmental programmes by modulating hormonal response pathways. However, their precise role and position within the sex-regulatory hierarchy are yet to be clarified. The multi-layered regulation of sex determination in Cannabis sativa L. provides a valuable framework for investigating the molecular basis of this process through the integration of genetic, environmental, and hormonal factors. A more comprehensive understanding of these interacting regulatory layers may facilitate the development of strategies for early sex identification, improved control over flower sex conversion, and the optimisation of cannabinoid-rich female inflorescence production. Such advances would support both fundamental and applied approaches in Cannabis biotechnology and cultivation.