Insights Into Walnut Lipid Metabolism From Metabolome and Transcriptome Analysis.

Suxian Yan,Chenkang Yang,Jun Zheng,Jiajia Zhao,Xingwei Zheng,Bangbang Wu,Ying Wang,Ling Qiao,Junyou Wang,Huming Zhi,Jianguo Xu,Xingsu Wang,Pourkheirandish Mohammad

doi:10.3389/fgene.2021.715731

Abstract

Walnut oil is an excellent source of essential fatty acids. Systematic evaluation of walnut lipids has significance for the development of the nutritional and functional value of walnut. Ultra-performance liquid chromatography/Orbitrap high-resolution mass spectrometry (UHPLC-Orbitrap HRMS) was used to characterize the lipids of walnut. A total of 525 lipids were detected and triacylglycerols (TG) (18:2/18:2/18:3) and diacylglycerols (DG) (18:2/18:2) were the main glycerolipids present. Essential fatty acids, such as linoleic acid and linolenic acid, were the main DG and TG fatty acid chains. Many types of phospholipids were observed with phosphatidic acid being present in the highest concentration (5.58%). Using a combination of metabolome and transcriptome analysis, the present study mapped the main lipid metabolism pathway in walnut. These results may provide a theoretical basis for further study and specific gene targets to enable the development of walnut with increased oil content and modified fatty acid composition.

Highlights

As one of the four major nut crop species in the world, walnut (Juglans regia L.) is widely distributed in Asia, Europe, North America, and Africa
The results provide a reference for studying walnut functional lipid components and improving the nutritional quality of walnuts
The elution order of the same type of lipid molecules is determined by the number of carbon atoms and double bonds in the fatty acid chains

Summary

Introduction

As one of the four major nut crop species in the world, walnut (Juglans regia L.) is widely distributed in Asia, Europe, North America, and Africa. The cultivated area and yield of walnut rank first among all types of dried fruits, and the crop has high economic value (Martínez et al, 2010). The oil content of walnut kernels is 52–70% and walnut oil is an excellent source of essential fatty acids with high nutritional value. Dried walnuts are currently the most important walnut product. Less than 10% of dried walnuts are highly processed into walnut food. Walnut is a good source of vegetable oil, which can be used for cooking and as an ingredient in paint and cosmetics (Zambón et al, 2000). TG and DG constitute a good source of essential fatty acids of which

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