Localisation of hydrogen peroxide accumulation during Solanum tuberosum cv. Rywal hypersensitive response to Potato virus Y.

The reactive oxygen species hydrogen peroxide (H(2)O(2)) was detected cytochemically in Solanum tuberosum cv. Rywal tissues as a hypersensitive response (HR) 24 and 48 h after a Potato virus Y (PVY) infection. Hydrogen peroxide was detected in vivo by its reaction with 3.3-diaminobenzidine, producing a reddish-brown staining in contact with H(2)O(2). Hydrogen peroxide was detected in the necrotic area of the epidermal and mesophyll cells 24 and 48 h after the PVY infection. Highly localised accumulations of H(2)O(2) were found within xylem tracheary elements, and this was much more intensive than in non-infected leaves. Hydrogen peroxide was detected cytochemically in HR also by its reaction with cerium chloride, producing electron-dense deposits of cerium perhydroxides. Inoculation with PVY(NTN) and also PVY(N) Wi induced a rapid hypersensitive response during which highly localised accumulations of H(2)O(2) was detected in plant cell walls. The most intensive accumulation was present in the bordering cell walls of necrotic mesophyll cells and the adjacent non-necrotic mesophyll cells. Intensive electron-dense deposits of cerium perhydroxide were found along ER cistrenae and chloroplast envelopes connected with PVY particles. The precipitates of hydrogen peroxide were detected in the nuclear envelope and along tracheary elements, especially when virus particles were present inside. The intensive accumulation of H(2)O(2) at the early stages of potato-PVY interaction is consistent with its role as an antimicrobial agent and for this reason it has been regarded as a signalling molecule.