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]GA1/3 (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.