Glucose-6-Phosphate Dehydrogenase, Ribonucleases and Esterases upon Tobacco Mosaic Virus Infection and Benzothiodiazole Treatment in Tobacco

Abstract

Effect of the benzothiodiazole (BTH) pre-treatment was monitored during the acute infection stage in the susceptible and the hypersensitive tobacco plants infected with the tobacco mosaic virus (TMV). Dynamic changes in the contents of chlorophyll, the total proteins, and the pathogenesis related proteins (PR-proteins), and activities of ribonucleases (RNase), phosphomonoesterase (PME), phosphodiesterase (PDE), and glucose-6-phosphate dehydrogenase (G6P DH) were studied. Neither the protein nor the chlorophyll contents were significantly changed by the TMV infection and/or the BTH treatment. The BTH pre-treatment caused a substantial reduction in the multiplication of TMV in the locally-infected leaves of the hypersensitive cultivar Xanthi-nc (to 15.1%). A lesser decrease (to 50.3%) was observed in the locally-infected leaves of susceptible cultivar Samsun. But in the systemically-infected leaves of this cultivar, only a 4-d delay in the multiplication of TMV was found. In the locally-infected leaves of both cultivars, the activities of the RNase, PME, PDE and G6P DH were sharply increased during the acute phase of TMV multiplication (when compared with the healthy plants) and the curves of these activities correlated with the multiplication curves of TMV. The BTH alone also strongly enhanced the activities of these enzymes early after application. Only low additional increases in some enzymes and even slight declines in the others were observed when the inoculation of leaves of cultivar Xanthi-nc followed the pre-treatment with the BTH. No inhibition of the enzymes was observed when the direct effect of different concentration of the BTH (1 – 1000 μM) was examined in vitro during a measurement of the activity. The analysis of intercellular proteins by PAGE under native conditions shows the similar spectrum of the proteins extracted from either the BTH-treated or the TMV-infected tobacco cv. Xanthi-nc.