Effect of Ethylene and Ethylene Precursors on Protein Phosphorylation and Xylogenesis in Tuber Explants ofHelianthus tuberosus(L.)

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Abstract
Koritsas, V. M. 1988. Effect of ethylene and ethylene precursors on protein phosphorylation and xylogenesis in tuber explants of Helianthus tuberosus (L.).J. exp. Bot. 39: 375–386. The role of ethylene in protein phosphorylation and xylem-cell differentiation was studied in explant cultures of Jerusalem artichoke, Helianthus tuberosus (L.). Explants on xylem-inducing medium growing at 25 °C developed more xylem elements and produced more ethylene gas within 3 d of culture than control cultures growing and developing at similar rates. L-methionine and 1-aminocdopropane-1-carboxylic acid (ACC) incorporated into both xylem-inducing and control media enhanced xylem differentiation, increased protein levels and stimulated protein kinase activity in the explants. Inhibitors of the ethylene biosynthetic pathway, cobalt nitrate and aminoethoxyinyl glycine (AVG), depressed xylem differentiation, protein phosphorylation and polypeptide synthesis. Ethylene gas or ACC reversed the effects of the inhibitors. Ethylene production, protein phosphoryilation and xylem-cell differentiation were all linked. Ethylene thus promotes xylem-cell differentiation in Jerusalem artichoke explants, the process probably being regulated by protein phosphorylation.