Thyme Oil Alleviates Cadmium-Induced Disturbances in Mitotic Activity, Cytoskeletal Organization and H3T3/H3S10 Phosphorylation in Vicia faba.

Cadmium (Cd) contamination, through induction of oxidative stress, severely impairs plant growth. Using primary roots of Vicia faba, we investigated how a 24 h incubation in CdCl2 solution (175 µM) affects mitotic progression in meristems and assessed whether thyme essential oil (TO; 0.03%, v/v), as a natural antioxidant, can protect proliferating cells during simultaneous Cd exposure. Cd strongly inhibited root growth, reduced mitotic index tenfold (to 0.6%), induced chromatin condensation, decreased CDKA protein levels and CycB transcripts and proteins, caused pronounced microtubule bundling and alterations in their arrangement, disorganization of actin filaments, and disturbances in histone H3 phosphorylation (H3T3Ph, H3S10Ph). TO led to a partial recovery of mitotic index (to ~50% of the control), normalization of chromosome condensation, maintenance of cell-cycle regulators at near-control levels, preservation of proper cytoskeletal organization, and restoration of the correct H3 phosphorylation pattern. This enabled cells to progress from metaphase to anaphase and maintain phase proportions close to the control, resulting in normal root growth. These findings indicate that TO protects the mitotic cellular environment against Cd-induced disturbances. To the best of our knowledge, this is the first evidence that TO safeguards the plant mitotic apparatus under Cd stress, highlighting its potential as a natural bioprotective agent supporting plant growth.