Evidence Does Not Support Ethylene as a Cue for Synthesis of Alcohol Dehydrogenase and Pyruvate Decarboxylase During Exposure to Hypoxia

Abstract

Low O₂ concentrations increased the activity of alcohol dehydrogenase (ADH; EC 1.1.1.1) and pyruvate decarboxylase (PDC; EC 4.1.1.1), but exogenously applied ethylene did not reproduce this effect in either maize roots or rice coleoptiles. However, ethylene was clearly exerting its known effects on the maize roots, since it inhibited root extension, and promoted aerenchyma formation. Furthermore, treatment with silver nitrate, an antagonist of ethylene action, failed to inhibit the rise in ADH activity in O₂-deficient maize roots. We conclude that ethylene causes morphological adaptations to O₂-deficiency, but is not involved in concurrent increases in activities of ADH and PDC. Alternative causes for the increases in enzyme activity are proposed.