The Oleic/Linoleic Acid Ratio in Olive (Olea europaea L.) Fruit Mesocarp Is Mainly Controlled by OeFAD2-2 and OeFAD2-5 Genes Together With the Different Specificity of Extraplastidial Acyltransferase Enzymes.

M Luisa Hernández,José M Martínez-Rivas,Angjelina Belaj,M Dolores Sicardo

doi:10.3389/fpls.2021.653997

Abstract

Fatty acid composition of olive oil has an important effect on the oil quality to such an extent that oils with a high oleic and low linoleic acid contents are preferable from a nutritional and technological point of view. In the present work, we have first studied the diversity of the fatty acid composition in a set of eighty-nine olive cultivars from the Worldwide Olive Germplasm Bank of IFAPA Cordoba (WOGBC-IFAPA), and in a core collection (Core-36), which includes 28 olive cultivars from the previously mentioned set. Our results indicate that oleic and linoleic acid contents displayed the highest degree of variability of the different fatty acids present in the olive oil of the 89 cultivars under study. In addition, the independent study of the Core-36 revealed two olive cultivars, Klon-14 and Abou Kanani, with extremely low and high linoleic acid contents, respectively. Subsequently, these two cultivars were used to investigate the specific contribution of different fatty acid desaturases to the linoleic acid content of mesocarp tissue during olive fruit development and ripening. Fatty acid desaturase gene expression levels, together with lipid analysis, suggest that not only OeFAD2-2 and OeFAD2-5 but also the different specificities of extraplastidial acyltransferase enzymes are responsible for the variability of the oleic/linoleic acid ratio in olive cultivars. All this information allows for an advancement in the knowledge of the linoleic acid biosynthesis in different olive cultivars, which can impact olive breeding programs to improve olive oil quality.

Highlights

Olea europaea L. was one of the first plants to be cultivated for oil production
To further explore the diversity in the oleic/linoleic acid ratio in different olive cultivars, we decided to analyze the fatty acid composition of a Core-36, which holds most of the genetic diversity found in the WOGBC-IFAPA (Belaj et al, 2012) (Supplementary Table 2)
The oleic/linoleic acid ratio was inversely proportional to the linoleic acid content (Supplementary Table 2), clearly indicating that the variability of linoleic acid content found in the Core36 oils is mainly caused by different varietal capacities of oleate desaturase enzymes

Summary

Introduction

Olea europaea L. was one of the first plants to be cultivated for oil production. The olive tree is one of the most important and widespread fruit trees in the Mediterranean basin and, nowadays, is the second most important oil fruit crop cultivated worldwide (Baldoni et al, 2009). Global olive oil production and consumption have been growing considerably in recent decades thanks to its remarkable organoleptic, technological, and nutritional properties, which are determined by the metabolites present in the olive oil (Rallo et al, 2018). Among these metabolites, fatty acids that are esterifying triacylglycerols (TAG), which are the major components, are what largely determine the technological and nutritional properties of olive oil (Salas et al, 2000). Olive oils with high oleic and low linoleic acid content are better from a nutritional and technological point of view. The generation of new olive cultivars producing oils with high oleic/linoleic acid ratio is a priority in olive breeding programs

Methods

Results

Conclusion