Transcriptomic insights into unisexual flower development in Cannabis sativa: conserved MADS-box networks and divergent developmental programs

Background: Cannabis sativa, a dioecious species characterized by striking sexual dimorphism and exceptional sexual plasticity, presents a powerful model for exploring floral development and the evolution of dioecy. The unique male and female flowers each feature a single perianth whorl that differs significantly in structure and developmental trajectory, raising key questions about organ identity and developmental regulation that remain largely unresolved. Results: Analysis of MADS-box gene expression reveals that, despite sexual dimorphism and structural reduction, both sexes conform to the canonical ABCDE model of floral organ identity, indicating unisexual flower development relies on conserved regulatory networks. We further demonstrate that male flowers undergo more extensive transcriptional reprogramming than female flowers, suggesting a more complex developmental trajectory. By integrating molecular and morphological evidence, we provide support for a petaloid interpretation of the male perianth, offering new insight into the identity of the Cannabis floral organ. Conclusions: This study provides molecular and morphological evidence strongly suggesting that the male Cannabis perianth possesses petaloid characteristics, offering a new perspective on a key floral trait. Our findings demonstrate that despite structural reduction and unisexual development, Cannabis employs conserved ABCDE regulatory networks, suggesting that B-class genes link petal and stamen development. This work establishes a developmental-genetic framework for understanding the evolution of dioecy and highlights how wind pollination may drive perianth reduction while maintaining underlying genetic programs.