Linked activation of cell division and oxidative stress defense in alfalfa leaf protoplast-derived cells is dependent on exogenous auxin

Abstract

The activation of cell division and oxidative stress responses has been investigated in the case of leaf protoplast-derived cells. Initiation of protoplast culture was found to be associated with oxidative stress as indicated by the rate of H2O2 release into the medium and/or by catalase and ascorbate peroxidase activities. Both cell division frequency and the above stress-related parameters were dependent on the exogenous auxin (2,4-dichlorophenoxyacetic acid, 2,4-D) concentrations used. In addition, the well known oxidative stress-inducing agent paraquat (1 μM) could promote cell division at suboptimal auxin concentration but not in the absence of exogenous auxin. The H2O2 scavenger dimethylthiourea and the NADPH oxidase inhibitor diphenyleneiodonium inhibited not only the activation of cellular defense reactions but cell division as well. Based on the above experimental observations, it is suggested that exogenous auxin (2,4-D) enhances cellular defense reactions in parallel with cell division activation.