Abscisic acid and the accumulation, biological activity and metabolism of four derivatives of [^3H] gibberellin A_1 in barley aleurone layers

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Tritiated GA_1 and four of its synthetic derivatives were studied in relation to their biological activity, uptake and metabolism by barley aleurone layers. Incubation was done in the presence and absence of ABA. Tentative identification of some of the metabolites was made by TLC and GLC radiocounting of the metabolite and its acid hydrolyzed derivative. Only GA_1 promoted α-amylase synthesis. Uptake ranged from 20 to 42%, varying with the derivative. ABA enhanced uptake of [^3H]GA_1 and [^3H]pseudoGA_1 and inhibited uptake of [^3H]ketoGA_1, the Wagner-Meerwein rearrangement product of [^3H]-GA_1. Uptake of [^3H]GA_1 methyl ester ([^3H]GA_1-Me) and [^3H]dihydroGA_1, was unaffected by ABA. [^3H]GA_1 was converted to an amphoteric GA_1 derivative ([^3H]amphoGA_1) and [^3H]GA_1-glycosyl ester. GA_1-Me was metabolized to four products, all of them GA_1 derivatives, including an apparent amphoteric GA_1 derivative. DihydroGA_1 was quite stable; only one metabolite was produced in sufficient yield to analyze. This product did not cochromatograph with either of the expected acid hydrolyzed epimers of [^3H]-dihydroGA_1, [^3H]ketoGA_1 was readily metabolized to one product, probably the glycoside. [^3H]pseudoGA_1 remained essentially unmetabolized. Metabolism of all compounds tested was not dramatically affected by ABA. Surprisingly, no metabolites from hydroxylation at the 2-position were found.
日本植物生理学会の論文