LOCALIZATION OF OLIVE S-ADENOSYL METHIONINE DECARBOXYLASE AND SPERMIDINE SYNTHASE MRNA TRANSCRIPTS IN FLOWER OPENING AND DURING EARLY FRUIT DEVELOPMENT

Early fleshy-fruit growth conforms to a complex developmental program that involves cell division, restricted to an initial period of a few weeks after anthesis, followed by cell expansion. Polyamines (PAs) are required for cell growth and cell division in eukaryotic and prokaryotic organisms. The present study is aimed at understanding the developmental regulation of PA biosynthesis and catabolism during flower opening and early fruit development. Two full-length cDNA clones coding for S-adenosyl methionine decarboxylase (SAMDC) and spermidine synthase (SPDS) homologs, key steps in the PA biosynthesis pathway, in the stone-fruit of olive (Olea europaea L.) were identified and the spatial and temporal organization of these genes were described. In olive flowers, OeSAMDC gene transcripts were highly expressed in ovary wall, placenta and ovules, while OeSPDS transcript was confined to the ovules of ovary at the anthesis stage. OeSAMDC and OeSPDS transcripts were co-expressed in fruit mesocarp and exocarp at all developmental stages analyzed as well as in nucellus, integument and inner epidermis tissues of fertilized ovules. The results provide novel data about localization of PA biosynthesis gene transcripts, indicating that transcript levels of PA biosynthesis genes are all highly regulated in a developmental and tissue-specific manner.