RESUMO
The relative abundance of alpha-linolenic (alpha-LeA) compared with linoleic acid is associated with the developmental stage and the plant species and is proposed to have important physiological effects on both vegetative and reproductive plant development. The enzymes responsible for catalyzing the conversion of linoleic acid to alpha-LeA, the omega-3 fatty acid desaturases (FADs), are localized in the plastid or the endoplasmic reticulum (ER). Here we present the isolation of an ER-type omega-3 FAD gene (OeFAD3) from olive (Olea europaea L.). Expression patterns of OeFAD3 in different seed tissues and mesocarps during olive fruit development showed that its contribution to olive oil biosynthesis and modification is minimal. Regulation of OeFAD3 differed from that of its plastidial counterpart, being preferentially expressed in proliferating tissues, in concert with the active membrane biogenesis required for cell division. Trienoic acid-deficient Arabidopsis mutants are male sterile, because alpha-LeA-derived jasmonic acid (JA) is required for pollen development. However, the upregulation of OeFAD3 in different pistil tissues, particularly in vascular bundles and ovaries, rather than in anthers, implies a critical role of alpha-LeA in female gametophyte development in olive, corroborating results from JA-defective tomato mutants that are female sterile but not male sterile.
