Ethylene regulation of β-1,3-glucanase in tobacco

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Abstract
Ethylene treatment (approx. 20 μl ·1-1 in air for 2 d) of tobacco (Nicotiana tabacum L. cv. Havana 425) plants markedly increases the endo-β-1,3-glucanase (EC 3.2.1.39) content of leaves. The antigenic form of the enzyme induced is the same one whose production is blocked by treating cultured cells with combinations of auxin (1.1 · 10-5 M α-naphthaleneacetic acid) and cytokinin (1.4 · 10-6 M kinetin). Evidence is presented that cultured tobacco cells require ethylene for β-1,3-glucanase accumulation: i) ethylene treatment increased the accumulation of \-1,3-glucanase in callus tissues >10 d after subculturing and in cell-suspension cultures; ii) callus tissues can produce ethylene; iii) conditions known to inhibit ethylene production (1 mM CoCl2; 33° C treatment) or ethylene action (approx. 1.6 mmol · 1-1 norbornadiene in air) inhibited β-1,3-glucanase accumulation by callus tissues treated for 4 d following subculturing; and, these inhibitory effects were prevented by exogenous ethylene. Combinations of auxin and cytokinin blocked ethylene-induced accumulation of β-1,3-glucanase by cell-suspension cultures. The results favor a model in which ethylene induces results favor a model in which ethylene induces β 1,3-glucanase accumulation, and auxin and cytokinin inhibit this induction process.