RELATIONSHIP BETWEEN DEGRADATION OF RIBULOSE-BISPHOSPHATE CARBOXYLASEOXYGENASE AND SYNTHESIS OF AN ABUNDANT PROTEIN OF 23 KDA OF BARLEY LEAVES (HORDEUM-VULGARE CV SALOME) INDUCED BY JASMONATES

Barley leaf segments respond to treatment with jasmonate with the degr adation of ribulose-bisphosphate carboxylase/oxygenase (RUBISCO) down to less than 5% of untreated leaves after a three day incubation. Conc omitantly, the 23 kDa protein (JIP-23) among the newly synthesized jas monate-induced proteins (JIPs) reachs more than 25% of total leaf prot eins. Using pulse-labeling with S-35-methionine steady-statte specific radioactivities of RUBISCO and JIP-23 were compared to study whether or not amino acids released by RUBISCO degradation are directly used i n the synthesis of JIP-23. Pulse-labeled leaves synthesize JIP-23 upon jasmonate-treatment up to a three-fold higher specific radioactivity than that of RUBISCO. On the other hand, in leaves pretreated with 1 m M methionine followed by jasmonate-treatment specific radioactivity of JIP-23 exceeds that of RUBISCO only slightly. Furthermore, pulse-labe led leaves synthesize JIP-23 in the presence of jasmonate and unlabele d methionine to a significantly lower specific radioactivity than that after preloading with methionine. Data presented here argue against a direct use of amino acids released by degradation of RUBISCO for synt hesis of JIP-23. The results can be explained in terms of amino acid c ompartmentation.