The Potential of Cell Suspension Cultures of Daucus carota L. as a Source of Isotope Labelled Gibberellins. I. Metabolism of [³H]GA₅

Abstract

Gibberellin A₅ (GA₅), which is not known to be native to carrot (Daucus carota L.), was fed as either high specific activity [1-³H]GA₅ (HSA, 3.2 Ci/mmol) or low specific activity [1, 2-³H]GA₅ (LSA, 74 mCi/mmol) to cell suspension cultures of carrot. Gibberellins A₁, A₃, A₆, A₈ and their glucosyl conjugates were found as metabolites of HSA [³H]GA₅, as were GA₂₂, GA₂₉ and GA₅ glucoside and glucosyl ester, with all tentative identifications based on retention times on reversed phase C₁₈ HPLC with radiocounting. From LSA [1, 2-³H]GA₅ feeds, GA₁, GA₃, GA₆, GA₈ and GA₂₉ were identified by GC/SIM. For cells or medium, only 24 to 27%, respectively, of [³H]GA₅ was metabolized; major metabolites were [³H]GA₅ glucosyl conjugates (HSA and LSA feeds) and free [³H]GA_1/3 (LSA feeds). The system may thus be useful for production of labelled GAs and GA conjugates, and especially for conjugates of GA₅ and free GA₆ without dilution by endogenous GAs.