Gibberellin metabolism in excised lettuce hypocotyls: Evidence for the formation of gibberellin A1 glucosyl conjugates

Abstract

The properties of the water-soluble metabolites of [(3)H]gibberellin A1 ([(3)H]GA1) from lettuce (Lactuca sativa L.) hypocotyls were compared with those of authentic samples of gibberellin (GA) glucosyl esters and ethers. Partitioning against l-butanol at high and low pH was not an efficient method of differentiating between ester and ether conjugates of GA1 or GA3. Extraction into l-butanol at pH 2.5 was, however, useful as a group purification step. Gel-filtration on acrylamide indicated a mean molecular weight of ca. 600 for the polar material and high-voltage electrophoresis separated two compounds (LH 1 and LH 2) with differing charge properties. Both metabolites incorporated (14)C from glucose and (3)H from GA1. Subsequent enzymatic hydrolysis of LH 1 released material with identical properties to [(14)C]glucose together with a second uncharacterised component. Feeding with [(3)H]GA1 methyl ester greatly reduced the formation of LH 1 but not LH 2. The metabolites were provisionally identified as GA1-glucosyl ester (LH 1) and GA1-glucosyl ether (LH 2).