| The oxidative burst is a rapid, localized plant defense response. It is characterized by the production of hydrogen peroxide and other active oxygen species within minutes of elicitation. However, the relevance of the oxidative burst in cell culture to events that occur in whole plants has been questioned, so various methods of quantitating hydrogen peroxide were evaluated.;While much is known about the various signal transduction pathways of the oxidative burst, the involvement of phospholipase D, a major component of neutrophil oxidative burst signaling, had not been previously appraised in plants. No accumulation of its product, phosphatidic acid, was observed after elicitor addition. Furthermore, exogenous phosphatidic acid neither elicited a burst nor enhanced the OGA-activated burst.;Kinases and phosphatases have been shown to participate in the oxidative burst through pharmacological studies. A kinase which appears to be at a convergence point of the signaling cascade is characterized. This 42 kDa kinase has activity towards myelin basic protein on threonine residues, with minor phosphorylation on serine. It occurs downstream of an internal calcium release, as its activation can be blocked by the addition of internal calcium channel inhibitors. Its activation is partially due to phosphorylation on tyrosine residues, as a phosphoprotein of the same molecular weight appears during kinase activation, the kinase can be immunoprecipitated with antiphosphotyrosine antibodies, and treatment with a protein tyrosine phosphatase inactivates the kinase. The purification of this kinase via several column chromatography steps is also described. |
