Sex-specific responses in photosystem regulation, antioxidant defence, and energy metabolic adaptations in mulberry (Morus alba L.) to waterlogging stress

• Female Morus alba plants demonstrate superior tolerance to waterlogging stress through enhanced photosynthesis and oxidative stress defense mechanisms. • Female plants maintain better CO 2 assimilation and transpiration rates under waterlogging compared to male plants. • Female plants optimize non-photochemical quenching, preserving photosystem integrity, whereas males exhibit increased photoinhibition. • Proteomic analysis reveals that females upregulated key proteins (e.g., PsbB, PsbQ, PsaN, PetH) involved in stress tolerance, while males show downregulation of critical stress-responsive proteins. • Female plants exhibit more efficient energy production through enhanced glycolysis and TCA cycle activity under waterlogging stress, unlike males. Waterlogging stress is an increasingly common abiotic stress caused by climate change, significantly impairing physiological and metabolic processes, reducing growth and overall productivity. Previous studies have examined the physiological response of mulberry ( Morus alba L.) to waterlogging stress; however, sex-specific differences and underlying adaptive mechanisms remain underexplored. This study examines the sex-specific adaptive mechanisms of mulberry to waterlogging, focusing on photosystem regulation, antioxidant defence, and energy metabolism. The results showed that female plants exhibited greater waterlogging tolerance through a multifaceted strategy, whereas males showed systemic dysregulation in photosynthesis, antioxidant, and metabolic processes. The gas exchange analyses revealed that females optimized CO 2 assimilation through moderate stomatal regulation, maintaining higher intercellular CO 2 concentration. Chlorophyll fluorescence indicated higher non-photochemical quenching (NPQ) and stable Fv/Fm, preserving photosystem integrity. Furthermore, the proteomic profiling revealed upregulation of key photosynthetic proteins (e.g., PsbB, PsbQ, PsaN, PetH) in females, while males exhibited downregulation of photosystem components (PsbD, PsbH, PsaA/B). In antioxidant defence, females activated leucine aminopeptidase 3 and glutathione S-transferase, efficiently scavenging reactive oxygen species (ROS), while males showed impaired ROS management. In energy metabolism, females sustained ATP production under hypoxia through enhanced glycolysis and TCA cycle activity, while males showed metabolic disruptions. These findings indicate that female plants achieve superior stress tolerance through integrated regulation of photosystems, ROS homeostasis, and metabolic flexibility, offering insights for breeding waterlogging-resilient cultivars and contributing to ecological restoration in flood-prone ecosystems.