Peroxidases and photosynthetic pigments in susceptible potato infected with potato virus Y-NTN

The aim of this work was to investigate the activity of soluble, ionically- and covalently-bound peroxidases (EC 1.11.1.7), the protein content, and t he photosynthetic pigment metabolism in the potato (Solanum tuberosum L.) c v. Igor, at the time of local lesion development resulting from infection w ith potato virus Y-NTN. In comparison to intact plants, mock inoculation wi th the sap of healthy plants induced changes in peroxidase activity and met abolism of photosynthetic pigments which could, in most cases, be distingui shed from the changes induced by virus infection. An inverse correlation wa s observed between chlorophyll content and the activity of soluble and ioni cally-bound peroxidases. This activity increased while that of covalently-b ound peroxidase decreased, even in green leaves of infected plants which we re visibly unchanged, as well as in green leaves with local lesions. Lower chlorophyll content, and higher carotenoid to chlorophyll ratio than those in intact and mock-inoculated controls - signs of senescence - were observe d in leaves with local lesions and in yellow leaves of infected plants. Dif ferences in measured parameters in intact, mock-inoculated, and infected pl ants showed that processes induced by virus infection differ from those ind uced by mock inoculation, and that viral induced senescence is clearly not the same as natural senescence. (C) 2001 editions scientifiques et medicale s Elsevier SAS.