Abstracts now available online - Euro Fed Lipid

Linoleate biosynthesis and aroma biogenesis in olive fruit:
a molecular approach
José M. Martínez-Rivas, M. Luisa Hernández, María Padilla and Manuel Mancha
Instituto de la Grasa, CSIC, Sevilla, Spain
Olive oil is a vegetable oil with outstanding nutritional properties due to its well balanced
fatty acid composition, as well as the presence of minor components such as natural
antioxidants. In addition, olive oil is characterized by its unique organoleptic
characteristics including aroma, color and flavor. However, very little information is
available in olive fruit on the pathways involved in the biosynthesis of the compounds
responsible for these exceptional properties. We have initiated a program with the aim
of improving olive oil quality using a molecular approach.
The first goal is the reduction of linoleic acid in some olive cultivars which posses a
relatively high content of this fatty acid, yielding olive oils with low oxidative stability. To
achieve this three different cDNA sequences, encoding two microsomal (OepFAD2-1,
OepFAD2-2) and one plastidial (OepFAD6) oleate desaturases have been isolated.
Genomic Southern blot data are consistent with the presence of at least two copies of
each FAD2 gene and only one copy of the FAD6 gene in the olive genome. Expression
studies show that they are tissue and developmentally regulated. Possible differential
physiological roles related to their contribution to the linoleic acid content in different
tissues will be discussed.
On the other hand, we have started the molecular characterization of the lipoxygenase
(LOX) pathway in olive fruit, in relation to the biosynthesis of olive oil aroma. Two
different cDNA clones with homology to 9-LOX and 13-LOX respectively, have been
isolated. In addition, a sequence that shows homology to 13-hydroperoxide lyases has
also been cloned. The physiological function of these genes regarding their contribution
to the olive oil aroma will be discussed.