Activity of β-1, 3-Glucan Hydrolase and Acquired Resistance in the Upper Leaves of Nicotiana glutinosa Followed by Infection with Tobacco Mosaic Virus

Abstract

When the lower leaves of Nicotiana glutinosa were inoculated with an ordinary strain of tobacco mosaic virus (TMV), β-1, 3-glucan hydrolase activity increased in the upper leaves of the same plant. The increase in enzyme activity was first detected 4 days after inoculation of the lower leaves, reaching a maximum of 6 times higher than the mock-inoculated control plants 10 days after the inoculation. The enzyme activities of the intercellular fluid (ICF) and of the rest of the tissue homogenates of both the inoculated lower leaves and the uninfected upper leaves of the plant increased with the progress of infection. The enzyme activity of ICF in the inoculated lower leaves was 6-10% of the total activity and in the upper leaves 7-11%. Acquired systemic resistance in the upper leaves to TMV appeared 4 days after inoculation of the lower leaves with TMV. Ten days after inoculation the size of local lesions in the upper, virus-challenged leaves decreased to 50% of the control. However, when the inoculated lower leaves were cut off the 2nd day after inoculation, no increase of the enzyme activity in the upper leaves was detected and no acquired resistance to TMV was observed. The relationship between β-1, 3-glucan hydrolase activity and the acquired resistance to TMV-infection is discussed.