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

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 [(14)C]GA(12)-7-aldehyde ([(14)C]GA(12)ald) to biologically active GAs. The metabolism of GAs early in the biosynthetic pathway, [(14)C]GA(12) and [(14)C]GA(12)ald, was investigated in pericarp tissue isolated from 4-day-old pea fruits. [(14)C]GA(12)ald was metabolized primarily to [(14)C]GA(12)ald-conjugate, [(14)C]GA(12), [(14)C]GA(53), and polar conjugate-like products by isolated pericarp. In contrast, [(14)C]GA(12) was converted primarily to [(14)C]GA(53) and polar conjugate-like products. Upon further investigations with intact 4-day-old fruits on the plant, [(14)C]GA(12) was found to be converted to a product which copurified with endogenous GA(20). Lastly, [(2)H]GA(20) and [(2)H]GA(1) were recovered 48 hours after application of [(2)H]- and [(14)C]GA(53) 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.