Differential Protein and Morphological Responses of Mosses to Heavy Metal Exposure: Insights from SDS-PAGE Analysis and Microscopic Examination

Heavy-metal pollution poses significant risks to ecosystems and human health. We evaluated acute proteomic and cytological responses of two mosses, Ectropothecium dealbatum and Hyophila involuta, to cadmium (Cd), lead (Pb), and zinc (Zn). Gametophores were immersed for 72 h to single-metal solutions (10, 20, or 30 mg/L; controls in distilled water), ensuring observed effects reflected single-metal toxicity. Protein profiles were resolved by SDS-PAGE, and light microscopy quantified chloroplasts per lamina cell and the proportion of dead cells. Cd elicited the strongest responses in both species, with intensified high-molecular-weight bands (~90, ~100, ~121 kDa) and pronounced cytological injury; Pb produced qualitatively similar but weaker changes. In contrast, Zn primarily modulated band intensity without generating new bands and caused limited injury at the tested doses. Concordant shifts across methods—reduced chloroplast counts and elevated lamina cell death co-occurring with Cd/Pb-associated bands—support a molecular–physiological linkage of acute metal stress. However, these high-molecular-weight bands (including the ~121 kDa signal) are size-based, putative markers only; independent identification (e.g., LC-MS/MS or immunodetection) and functional validation are still required. Within this 72-h window and concentration range, sensitivity followed Cd > Pb ≫ Zn. The findings nominate candidate proteins for rapid discrimination of damaging (Cd, Pb) versus comparatively tolerated (Zn) exposures and motivate targeted protein identification plus longer, field-calibrated studies to establish biomonitoring thresholds.