Peroxidase Activity and Isoperoxidase Pattern in Tobacco Leaves Infected with Tobacco Necrosis Virus and Other Viruses Inducing Necrotic and Non‐Necrotic Alterations

Abstract

AbstractThe level of peroxidase activity was greatly enhanced in tobacco leaves infected by tobacco necrosis virus (TNV) and other viruses which induce necrotic symptoms (TMV, ToMV and PVYN). The intensity was related to the age of the leaves infected: absent or neglible in mature leaves and very pronounced in young growing infected leaves. On the contrary, changes in peroxidase activity were negligible when the infection was provoked by viruses which do not produce necrotic reactions (TMV and PVYO). Analysis of the peroxidase isoenzymes, pattern in tobacco leaves infected by TNV and other necrosis‐inducing viruses revealed in all cases, a slight increase in anionic (pl 3.5–3.7) and a considerable increase in moderately anionic isoenzymes particularly the pl 4.6 isoenzyme which in TNV and PVYN‐infected leaves reached levels up to 21 and 72 times the healthy control values. A considerable increase in the cationic (pl9.3–8.8) isoenzymes and the appearance of one moderately cationic isoenzyme (pl 8.2) was also detected. In leaf extracts from‐virus‐infected tobacco leaves with nonnecrotic response, no, or negligible alterations on the isoenzyme pattern were detected. However, infection by a fungal parasite (Erisyphe cichoracearum), which established a fully compatible, non‐necrotic, interaction with tobacco leaves, like the necrosis‐inducing viruses, changed the isoperoxidase pattern. The data suggest the necrotic alterations and associated changes in the peroxidase activity and isoperoxidase pattern in virus‐infected leaves are not clearly related.