Increase of β-1, 3-Glucan Hydrolase and Acquisition of Resistance in White Burley Leaves by Tobacco Mosaic Virus and Salicylate

Abstract

When the leaves of Nicotiana tabacum L. cv. White Burley were inoculated with a tomato strain of tobacco mosaic virus (TMV-T), activity of β-1, 3-glucan hydrolase was increased, but not with an ordinary strain of TMV (TMV-OM) and mechanical injury. An increase of the enzyme activity in uninoculated upper leaves of the same plants in which the lower leaves were inoculated with TMV-T, was positively correlated with acquired systemic resistance to TMV-T. Both sizes and numbers of local lesions produced on challenge-inoculated upper leaves decreased to about 30% of the control. However, when the inoculated lower leaves were cut off the 2nd day after TMV-T inoculation, no increase of the enzyme activity and systemic resistance in the upper leaves was observed. The enzyme activity was increased when detached half-leaves of the same plant were incubated on sodium salicylate solution, and showed a resistance to inoculated TMV-T. Furthermore, the enzyme activity was increased in the upper leaves of the same plant in which the lower leaves were injected with sodium salicylate and such the upper leaves showed the resistance to TMV-T. Polyacrylamide gel electrophoresis of the enzyme extracts from both the leaves inoculated with TMV-T and the leaves with induced resistance showed the presence of two isozymes of the glucan hydrolase. The involvements of salicylate on the increase of the enzyme activity and acquisition of the resistance to TMV-T are discussed.