Proteins functionally and immunogenically related to pathogenesis-related proteins are induced during parsley leaf senescence

The advancement of leaf senescence is accompanied by a reduction in cellular protein content together with the induction of specific proteins which are probably involved in the process. In the present study, with parsley, we followed the changes in the levels of proteins functionally and immunogenically related to pathogenesis-related proteins during both senescence of detached leaves and natural senescence of attached leaves. Both chitinase activity and protein level were found to be induced during senescence, as was the level of two other proteins immunologically related to beta-1,3-glucanase and P4 pathogenesis-related proteins of citrus and tomato, respectively. A high correlation between the advancement of senescence and the induction of these proteins was demonstrated. Treatments with CO2 or gibberellic acid, which retard senescence, reduced both chitinase activity and the level of the pathogenesis-related proteins, whereas enhancement of senescence with ethylene induced them further. The induction of pathogenesis-related proteins during senescence suggests that these proteins may have a primary role in this process.