Metabolism of [1,2-3H]gibberellin A4by epicotyls and cell-free preparations fromPhaseolus coccineusL. seedlings

✍ Scribed by Colin G. N. Turnbull; Alan Crozier

• Publisher: Springer-Verlag
• Year: 1989
• Tongue: English
• Weight: 722 KB
• Volume: 178
• Category: Article
• ISSN: 0032-0935
• DOI: 10.1007/bf00393203

✦ Synopsis

Cell-free systems were prepared from germinating seed and seedlings of Phaseolus coccineus. Gibberellin A4 (GA4)-metabolising activity was detected in vitro using preparations from roots, shoots and cotyledons of germinating seed, but only up to 24 h after imbibition. Cell-free preparations from cotyledons converted [3H]GA4 to GA1, GA34, GA4-glucosyl ester and a putative O-glucoside of GA34, and, in addition converted [3H]GA1 to GA8. Preparations from embryo tissues contained 2/%hydroxylase activity, converting [3H]GA4 to GA34 and [3H]GA~ to GAs.

The presence of GA-metabolising enzymes was also indicated by in-vivo feeds of [3H]GA4 to epicotyls of intact 4-d-old seedlings, which resulted in the accumulation of GA~, GA8, GAa-3-O-glucoside, GA4-glucosyl ester, GA8-2-O-glucoside and a putative O-glucoside of GAa4. Gibberellin A~ was the first metabolite detected, 15 min after application of [3H]GA4, but after 24 h most of the label was associated with GA8-2-O-glucoside. Over 90% of the recovered radioactivity was found in the shoot. Within the shoot, movement was preferentially acropetal, and was not dependent upon metabolism of the applied [3H]GA4.