DIFFERENCES IN PROTEIN-SYNTHESIS AND PEROXIDASE ISOENZYMES BETWEEN RECALCITRANT AND REGENERATING PROTOPLASTS

The reasons for the inability of recalcitrant mesophyll protoplasts to divide and re-enter the cell cycle are unknown. Changes in protein pr ofile, indole-3-acetic acid (IAA)-oxidase and peroxidase activities, a nd isoenzymes were compared in protoplasts of recalcitrant grapevine ( Vitis vinifera L. cv. Sultanina) and regenerating tobacco (Nicotiana t abacum L. cv. Xanthi). Using [S-35]-methionine, SDS-PAGE and two-dimen sional separation of proteins, differences in protein profile during p rotoplast culture were assessed. The changes in the de novo synthesize d proteins were both qualitative and quantitative between the two spec ies. The number of proteins which changed was double in tobacco compar ed to grapevine protoplasts. Peroxidase and IAA-oxidase activities inc reased significantly in tobacco protoplasts during culture whereas in grapevine they remained low. In tobacco protoplasts, 3 and 7 basic and acidic peroxidases, respectively, were induced during protoplast cult ure, which were not detected in the intact leaf, whereas in grapevine no new peroxidases were induced during protoplast culture.