Ethylene regulation of wound-induced ribonuclease in turnip root tissue

Exogenous ethylene enhances the synthesis of wound-induced ribonuclease (RNase) (EC2.7.7.16) in tissue discs of white turnip (Brassica rapa L. var. rapa (L.) Tell.). The half-maximal concentration is <0.01 μl/l ehtylene. Maximal response was obtained with either continuous ethylene treatment, or a 90-min pulse of ethylene followed by flushing with 1500 cm(3) of air/min at standard pressure or 500 cm(3)/min at hypobaric pressure for the remainder of the experiments. Addition of ethylene at 60-75 min after cutting had no effect on RNase activity. Also the effect of ethylene in enhancing RNase decreased about linearly when addition of ethylene was delayed for tissue discs. Since actinomycin-D inhibition of RNase synthesis, observed earlier, is also limited to the initial 45-60 min after cutting, these results are consistent with the view that ethylene is acting at transcription.