STRESS AND AGE-RELATED SPOTS WITH IMMUNOREACTIVITY TO UBIQUITIN-ANTIBODY AT PROTOPLAST SURFACES

Mesophyll protoplasts from primary leaves of 2, 3, and 4 week old Vici a faba L. plants and from not expanded leaves of 2 week old plants wer e incubated with rabbit anti-ubiquitin antibody and FITC labeled goat anti-rabbit IgG. Dependent on age of the plant material, an increase i n size and number of immunoreactive spots at protoplast surfaces were observed, when incubations were performed after 16 h storage to allow protoplast to recover. A relationship between isolation stress and the intensity of immunolabeling was demonstrated for protoplasts from not expanded leaves. Furthermore, the surface of isolation stressed proto plasts showed an increasing number of immunoreactive spots when plants were previously exposed to water deficiency conditions for 1, 2 or 4 days. Water deficiency conditions and isolation stress are therefore t hought to induce ubiquitination of surface located proteins. A phenome non, which seemed to be normally correlated with early events of senes cence.