Identification and Functional Characterization of the GPAT Gene Family in Regulating Oil Biosynthesis in Olive

Olive (Olea europaea L.) is one of the oldest woody oil crops. Previous studies, by integrating transcriptomics and metabolomics, have identified glycerol-3-phosphate acyltransferase 4 (GPAT4) as a key regulatory gene involved in oil biosynthesis in olive fruits. Although GPAT4 was identified as a key regulator, the overall function of the GPAT gene family in olive remains largely unknown. As a critical rate-limiting enzyme catalyzing triacylglycerol production, GPAT plays an important role in oil synthesis in oil crops. However, the function of the GPAT gene in olive remains unclear. A systematic analysis of the olive GPAT gene family showed that 12 OeGPAT proteins can be divided into four subclasses, all containing the conserved GPAT domain. These genes are distributed across chromosomes and scaffolds, with highly conserved motifs and variable gene structures. Functional studies revealed that overexpression of OeGPAT1.1, OeGPAT1.2, OeGPAT2, OeGPAT3, OeGPAT4, OeGPAT7, and OeGPAT8 significantly increased total oil content in transgenic Arabidopsis leaves and seeds. Further experiments in olive fruit at maturity stages II, III, and IV demonstrated that overexpression of the same set of OeGPAT genes elevated total oil content, while their silencing resulted in a decrease. In summary, this study reveals that OeGPATs can serve as ideal targets in metabolic engineering to regulate oil content in oil crops, providing a theoretical foundation for further research on oil biosynthesis in olive fruit.