Sex-Specific Ethylene Responses Drive Floral Sexual Plasticity in Cannabis

Cannabis sativa L. exhibits remarkable sexual plasticity: both XX and XY individuals can undergo complete phenotypic sex reversal in response to ethylene modulation. While this phenomenon is well documented, the molecular mechanisms remain underexplored. Here, we present the first multi-omic study of hormonally induced sex change in both XX and XY Cannabis plants, integrating transcriptomic profiling, ethylene pathway metabolite quantification, and whole-genome sequencing across three genetically distinct genotypes. Treatments with silver thiosulfate (STS) and ethephon induced >80% phenotypic conversion, but transcriptomic responses diverged sharply between chromosomal sexes. We profiled 47 ethylene-related genes (ERGs) and identified 14 high-confidence candidates--including CsACS1, CsACO5, CsERF1, and CsMTN--with sex-specific, time-dependent expression patterns that support a two-phase model of plasticity: early transcriptional reprogramming followed by stabilization of new floral identities. Several candidate ERGs were in non-recombining regions of the X chromosome or absent from the Y, while most showed low nucleotide diversity, suggesting functional constraint. These findings provide a high-resolution view of ethylene-responsive sex plasticity and demonstrate that convergent floral phenotypes arise from distinct regulatory programs in XX and XY plants. Our work advances the molecular understanding of sexual plasticity in dioecious species and identifies candidate genes for the development of sex-stable cultivars in Cannabis and other crops.