Sexual Dimorphism of Chloroplast Proteome Responses to Manganese Stress in Poplar Female and Male Sibling Lines

Manganese (Mn), an essential micronutrient, becomes toxic to plants in excess. The molecular mechanism underlying sex-specific responses of dioecious plants to Mn toxicity remains unclear. Here, we used chloroplast proteomics to explore physiological and molecular differences in Mn stress responses between female and male sibling lines of Populus euramericana, exposed to high Mn for four weeks. Females showed more severe leaf damage, reduced shoot growth, and decreased net photosynthetic rate (Pn), chlorophyll content, and peroxidase (POD) activity, with 76% of Mn sequestered in roots. In contrast, males maintained stable photosynthesis and POD activity, allocating 24% of Mn to leaves. Chloroplast proteomics identified 50 female-specific differentially expressed proteins (DEPs) enriched in pigment biosynthesis, photosynthesis, and stress responses, while males had 35 specific DEPs involved in photosynthesis, carbohydrate metabolism, and protein refolding. Males uniquely upregulated key proteins (chlNADP-MDH, PRK, and FBPase-like) linked to photosynthetic efficiency, whereas these pathways were repressed in females. Our findings revealed that females are more susceptible to Mn stress, while males exhibit greater tolerance via distinct Mn allocation and chloroplast proteomic adaptations.