SEED EFFECTS ON GIBBERELLIN METABOLISM IN PEA PERICARP

Pea fruit (Pisum sativum L.) is a model system for studying the effect of seeds on fruit growth in order to understand coordination of organ development. The metabolism of C-14-labeled gibberellin A12 (GA12) by pea pericarp was followed using a method that allows access to the seeds while maintaining pericarp growth in situ. Identification and quantitation of GAs in pea pericarp was accomplished by combined gas chromatography-mass spectrometry following extensive purification of the putative GAs. Here we report for the first time that the metabolism of [C-14]GA12 to [C-14]GA19 and [C-14]GA20 occurs in pericarp of seeded pea fruit. Removal of seeds from the pericarp inhibited the conversion of radiolabeled GA19 to GA20 and caused the accumulation of radiolabeled and endogenous GA19. Deseeded pericarp contained no detectable GA20, GA1, or GA8, whereas pericarp with seeds contained endogenous and radiolabeled GA20 and endogenous GA1. These data strongly suggest that seeds are required for normal GA biosynthesis in the pericarp, specifically the conversion of GA19 to GA20.