The identification and metabolism of GA9 and its metabolites in seed coats and shoots of pea, line G2

Abstract

H]gibberellin A 9 was applied to shoots or seed parts of G2 pea to produce radiolabeled metabolites. These were used as markers during purification for the recovery of endogenous GA9 and its naturally occurring metabolites. GA9 and its metabolites were purified by HPLC, derivatized and examined by GC-MS . Endogenous GA 9 , GA20 , GA29 and GA 51 were identified in pea shoots and seed coats . GA, -catabolite and GA.-catabolite were also detected in seed coats . GA70 was detected in seed coats following the application of lug of GA9 . Applied ['H]GA9 was metabolized through both the 13-hydroxylation and 2/3-hydroxylation pathways. Labeled metabolites were tentatively identified on the basis of co-chromatography on HPLC with endogenous compounds identified by GC-MS . In shoots ['H]GA S, and ['H]GAS , -catabolite were the predominant metabolites after 6 hrs, but by 24 hrs there was little of these metabolites remaining, while ['H]GA29catabolite and an unidentified metabolite predominated . In seed coats ['H]GA 51 was the initial product, later followed by ['H]GA 51 -catabolite and an unidentified metabolite (different from that in shoots), with lesser amounts of ['H]GA20 , ['H]GA 29 and ['H]GA 29 -catabolite . ['H]GA70 was a very minor product in both cases. ['H]GA 9 was not metabolized by pea cotyledons .

Metabolism of Gibberellin A12 and A12-Aldehyde in Developing Seeds of Pisum sativum L.

“…This is confirmed by the levels of non-13-hydroxylated GAs in the cotyledons: no GA5I or GA5,-catabolite was detected, which is in agreement with the lack of metabolism of [3H]GA9 by cotyledons (29), and the level of GA9 was low.…”

“…Second, both GA51 and GA5 -catabolite may possibly serve as substrates for a direct 13-hydroxylation to produce GA29 and GA29-catabolite, respectively. This is supported by the observation that in 3-to 24-h incubations of [3HJGA9 with seed coats, the peaks representing GA5, and GA5,-catabolite decrease substantially, whereas peaks representing GA29 and GA29-catabolite increase (29 (Fig. 2).…”

“…been the subject of numerous studies. Earlier work has shown that there are 11 GAs present in developing pea seeds, namely, GA., GA,,, GA2-aldehyde, GAI7, GA,9, GA,(, GA,9, GA29-catabolite, GA44, GA5,, and GA53 (5,8,9,15,18,24,25,26,29,30). The levels of those GAs, especially of GA2N, GA29, and GA2,-catabolite, were found to be substantially higher in immature seeds than in other parts of the plant (5).…”