The induction of the oxidative burst by oligogalacturonic acid elicitors
Abstract
We show here that oligogalacturonic acid (OGA) fragments comprised of 5 to 15 monomeric units induce the oxidative burst in tobacco and soybean cell suspension cultures. In soybean cultures, we show that OGA binds specifically and saturably to isolated microsomal membranes with a Kd of 2.36 μM. Optimal binding is seen in the presence of 1.5 mM calcium at pH 4.8. Inactive fragments of OGA neither compete for binding nor antagonize burst activity. We further show that calcium entry into the cytoplasm, activation of a 42 kDa kinase, and stimulation of oxidative burst activity are a function of the oligomeric size of the elicitor in both soybean and tobacco cell suspensions. The most active fragments in eliciting a burst in soybean and tobacco are a 7mer and a 9mer, respectively, as determined by FAB mass spectrometry. Additionally, these fragments were also most active in inducing the calcium flux and kinase activation in the respective cell suspensions. The calcium channel blocker, lanthanum, was found to block the calcium flux and the oxidative burst in tobacco cells at a concentration of 2 mM. The kinase inhibitor, staurosporine, block the burst in both cell suspensions at a concentration of 20 μM. Further, lanthanum blocks kinase activation, suggesting that the calcium flux is upstream of kinase activation in the signal transduction pathway leading to the oxidative burst.
Degree
Ph.D.
Advisors
Heinstein, Purdue University.
Subject Area
Botany|Molecular biology|Biochemistry
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