Oxidative stress inducing agents’ copper and alloxan accelerate cell cycle re-entering of somatic plant cells in the presence of suboptimal exogenous auxin

The physiological status of differentiated somatic plant cells and kinetics of re-entering in cell cycle were investigated in the case of Medicago sativa leaf protoplasts after the application of oxidative stress-inducing agents. Excess copper (30 μ M) and alloxan (0.5 mM) accelerated cell cycle re-entry at an exogenous auxin concentration that alone was insufficient to induce cell activation. Application of stress-inducing agents accelerated changes in the nuclei landscape with further faster re-entry in DNA replication and cytokinesis. This acceleration was accompanied by a lower level of reactive oxygen species (ROS) accumulations. At later stages, stress-agents treated cells resemble stem cells in planta with a smaller size, higher cell viability, lower ROS level, and lower activities of major ROS scavenging enzymes. A similar cellular response could be achieved by increasing the exogenous auxin concentration. Based on these experimental results, it is suggested that sub-lethal stress treatments evoke a transient cell state that accelerates cellular reprogramming. We also speculate that this transient cell state serves as an effective mechanism for protection against oxidative stress.