Polyamines, ribonuclease and the improvement of oat leaf protoplasts

L-arginine and L-lysine delay spontaneous lysis of oat leaf protoplasts, preserve uniformity of chloroplast distribution in protoplasts and prevent protoplast aggregation and adhesion to the substratum. Osmotic shock, exogenous RNAase and cell-free centrifugal supernatant fractions of mechanically-lysed protoplasts all induce protoplast lysis; arginine and lysine protect against these stresses as well. Arginine and lysine also produce effects at the metabolic level that may be related to their morphological stabilization of protoplasts. For example, the RNAase activity of freshly extracted oat leaf protoplasts is low, but rises progressively as the protoplasts are incubated in vitro; the same rise occurs during incubation of excised leaves prior to protoplast extraction. The RNAase increase in both systems can be prevented by 10-50 mM L-arginine or L-lysine. Concomitantly, these compounds support higher levels of incorporation of [³H] uridine into RNA. All the above effects can also be produced by polyamines (putrescine, cadaverine and spermidine) which are metabolically related to lysine and arginine; spermine is less effective at the concentrations tested.