Metabolome and Transcriptome Analyses Reveal Metabolomic Variations and Key Transcription Factors Involved in Lipid Biosynthesis During Seed Development in Carya illinoinensis

Plant oils are a large group of neutral lipids that play a vital role in the food and oleochemical industries. The pecan (<i>Carya illinoinensis</i>) is a promising woody oil crop known for its high-quality sources of essential fatty acids and various bioactive compounds that may aid in preventing heart diseases. However, there is still a lack of understanding regarding the accumulation of lipids and the molecular mechanism of lipid biosynthesis during seed development. This study aims to analyze the metabolite variations and molecular mechanisms of lipid biosynthesis by integrating untargeted metabolomics and transcriptomics during pecan seed development. A total of 293 differentially accumulated metabolites were identified and further categorized into 13 groups, with lipids and lipid-like molecules constituting the largest group. The oil content and fatty acid compositions of pecan embryos were assessed at three stages of seed development. Oleic acid (c18:1) and linoleic acid (c18:2n6) were found to be the most abundant unsaturated fatty acid components in pecan embryos. Additionally, a comprehensive analysis revealed 15,990 differentially expressed genes, with a focus on the key genes related to lipid metabolism. Furthermore, the study identified 1201 transcription factors from differentially expressed genes. These transcription factors were divided into 65 families, with different members in the same family exhibiting different expression patterns during seed development. The expression patterns of ten transcription factor genes during seed development were verified by qRT-PCR. Two key genes, <i>CiABI3</i> and <i>CiFUS3</i> were further cloned and found to be localized in the nucleus. This study used metabolome and transcriptome analysis during key periods of pecan seed development to identify the key genes associated with seed development and fatty acid biosynthesis.