Immunocytochemical localization of the pathogenesis-related PR-1 protein in barley leaves after infection by Bipolaris sorokiniana

A pathogenesis-related PR-1 protein accumulates in barley (Hordeum vulgare L.) leaves upon pathogen attack. The hyphae of Bipolaris sorokiniana invades primarily the intercellular space of mesophyll tissue. Light microscopy revealed that infected leaves show PR-1 labeling on mesophyll cell walls and both infected and non-infected leaves show labeling in chloroplasts. Subcellularly, PR-1 was detected on the outer cell wall layer and cytoplasm of primary hyphae, on intercellular electron dense material in junctions between host cells and in host cell wall appositions. The role of PR-1, as a defense and/or senescence related protein, in relation to its subcellular localizations is discussed.