Metabolomics and Transcriptomics Analyses Reveal Regulatory Networks Associated with Fatty Acid Accumulation in Pecan Kernels

Pecans are a globally important tree nut crop. Pecan nuts are rich in fatty acids (FAs), proteins, and flavonoids in addition to thiamine and numerous micronutrients. Although several of these nutriments have been studied in this plant, the comprehensive metabolite variations and molecular mechanisms associated with them have not been fully elucidated. In this study, untargeted metabolomics and transcriptomics were integrated to reveal the metabolite accumulation patterns and their associated molecular mechanisms during pecan kernel development. In total, 4260 (under positive mode) and 2726 (under negative mode) high quality features were retained. Overall, 163 differentially accumulated metabolites were identified. Most components were classified into the categories "organic acids and derivatives" and "lipids and lipid-like molecules." The accumulation patterns of amino acids, FAs, carbohydrates, organic acids, vitamins, flavonoids, and phenylpropanoids alongside embryo development were determined. Furthermore, transcriptomes from four pecan kernel developmental stages were used to assess transcript expression levels. Coexpression analyses were performed between FAs and their related genes. This study provides a comprehensive overview of the metabolic changes and regulations during pecan kernel development. We believe that the identification of nutriment accumulation trends and hub genes associated with the biosynthesis of the components will be valuable for genetically improving this plant.