Lipidomic and transcriptomic analysis of triacylglycerol accumulation mechanism of pecan (Carya illinoinensis) nut

Pecan (Carya illinoinensis) holds significant prominence as an oil-seed nut, characterized by its high content of fatty acids and triacylglycerol (TG). The inclusion of TG in the C. illinoinensis nut is of paramount importance, not only contributing significantly to the nutritional value for human consumption but also serving as a reliable and eco-friendly resource for various industrial uses. The present study conducted a comprehensive analysis involving transcriptomics, lipidomics, and physiological assessments to explore the dynamic patterns and components of triacylglycerols (TG) in C. illinoinensis nuts throughout the ripening phase. Additionally, the investigation aimed to elucidate the molecular mechanisms governing TG metabolism. The physiological investigation conducted on the maturation progression of three cultivars of C. illinoinensis unveiled distinctive traits within each variety. Notably, 'Mahan' displayed elevated concentrations of oil and crude fat, in contrast to the contrasting trend observed in 'Y-01'. Further lipidomic scrutiny exposed that 'Mahan' exhibited augmented levels of glycerides, specifically triglycerides (TG), monoacylglycerol (MG), and diacylglycerol (DG), compared to its counterparts during the ripening phase. The comparative analysis of RNA-Seq libraries uncovered a notable increase in unigenes associated with the 'glycerolipid metabolism' pathway. Moreover, the amalgamation of transcriptomic and lipidomic information indicated a heightened expression of genes implicated in TG metabolism in 'Mahan'. Moreover, there was a strong association between CiGPAT3, CiDGAT1, CiTAGL2, and CiMAGL1 genes and TG metabolism during the ripening process of C. illinoinensis nuts. Utilizing weighted gene co-expression network analysis (WGCNA) identified six distinct modules linked to various ripening stages, alongside the discovery of ten transcription factor families implicated in regulating TG metabolism. In summary, our research provides significant insights into the molecular framework that governs the accumulation mechanism of triglycerides (TG) in C. illinoinensis nuts throughout the ripening phase, which plays a pivotal role in optimizing the yield of C. illinoinensis oil and fostering progress in the molecular breeding.