[14C]GA12-Aldehyde, [14C]GA12, and [2H]- and [14C]GA53 Metabolism by Elongating Pea Pericarp

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Abstract
Gibberellins (GAs) are either required for, or at least promote, the growth of the pea (Pisum sativum L.) fruit. Whether the pericarp of the pea fruit produces GAs in situ and/or whether GAs are transported into the pericarp from the developing seeds or maternal plant is currently unknown. The objective of this research was to investigate whether the pericarp tissue contains enzymes capable of metabolizing GAs from [14C]GA12-7-aldehyde ([14C]GA12ald) to biologically active GAs. The metabolism of GAs early in the biosynthetic pathway, [14C]GA12 and [14C]GA12ald, was investigated in pericarp tissue isolated from 4-day-old pea fruits. [14C]GA12ald was metabolized primarily to [14C]GA12ald-conjugate, [14C]GA12, [14C]GA53, and polar conjugate-like products by isolated pericarp. In contrast, [14C]GA12 was converted primarily to [14C]GA53 and polar conjugate-like products. Upon further investigations with intact 4-day-old fruits on the plant, [14C]GA12 was found to be converted to a product which copurified with endogenous GA20. Lastly, [2H]GA20 and [2H]GA1 were recovered 48 hours after application of [2H]- and [14C]GA53 to pericarp tissue of intact 3-day-old pea fruits. These results demonstrate that pericarp tissue metabolizes GAs and suggests a function for pericarp GA metabolism during fruit growth.