C7(P32) and C6(P34) PR proteins induced in tomato leaves by citrus exocortis viroid infection are chitinases

[EN] Two chitinases induced in tomato leaves (Lycopersicon esculentum Mill cv. Rutgers) by citrus exocortis viroid (CEV) infection were purified. Their molecular masses determined by sodium dodecyl sulfate-gel electrophoresis were 32 kDa and 34 kDa and by filtration through Sephadex G-100 were 23 kDa and 25 kDa, respectively. These chitinases (P32 and P34) have been shown to be identical to the tomato pathogenesis-related proteins C7 and C6. They were purified in three stages: ammonium sulphate fractionation, chitin affinity chromatography and CM-Sepharose chromatography. The characterization of P32, the major component of the CEV-induced chitinase activity, revealed a basic protein (pI, 8·…