Identification of a soluble, high-affinity salicylic acid-binding protein in tobacco.

摘要

A new salicylic acid (SA) binding protein was identified in tobacco leaves. This soluble protein was present in low abundance and had an apparent molecular weight of approximately 25 000 Da. It reversibly bound SA with an apparent dissociation constant of 90 nM, an affinity that is 150-fold higher than that between SA and catalase. The ability of most analogues of SA to compete with labelled SA for binding to this protein correlated with their ability to induce defence gene expression and enhancedresistance. Strikingly, benzothiadiazole, a recently described chemical activator that induces plant defences and disease resistance at very low rates of application, was the strongest competitor, being much more effective than unlabelled SA. The possible role of this SA-binding protein in defence signal transduction is discussed.