H2O2 activates a MAP kinase-like enzyme in Arabidopsis thaliana suspension cultures

Treatment of Arabidopsis thaliana suspension cultures with H2O2 results in the activation of a 44 kDa protein kinase with the characteristics of a mitogen activated protein (MAP) kinase. It preferentially phosphorylates myelin basic protein as an artificial substrate, it requires tyrosine phosphorylation for its activity, is tyrosine and threonine phosphorylated upon activation, and its activation is rapid, transient, and occurs in a dose-dependent manner. This is the first demonstration of the activation of a MAP kinase-like enzyme by H2O2 in plants.