Characterization of the Glutamate Decarboxylase (GAD) Gene and Functional Analysis of <i>DlGAD3</i> in the Accumulation of γ-Aminobutyric Acid in Longan (<i>Dimocarpus longan</i> Lour.) Pulp
2025
Weilin Wei | Tingting Zhang | Yongping Chen | Ziqi Zhou | Wenbing Su | Qizhi Xu | Yaling Zhang | Shaoquan Zheng | Jimou Jiang | Chaojun Deng
γ-aminobutyric acid (GABA) is a four-carbon non-protein amino acid, with many regulatory effects in humans. It aids in regulating blood glucose levels and pressure and is widely recognized for its ability to promote cognitive balance through the alleviation of stress and improvements in sleep quality. The GABA content of longan pulp is higher than that of many other fruits and vegetables; however, much is still unknown about GABA’s biosynthesis in longan. In this study, we found that the GABA content of ‘Baoshi No. 1’ (BS1) pulp was significantly higher than that of ‘Chunxiang’ (CX) pulp. The GAD activity was higher in BS1 pulp than CX pulp, while there was no significant difference in the GABA-T activity. Additionally, five <i>GAD</i> genes were identified in longan, and an analysis of their transcriptional levels showed that only the expression level of <i>DlGAD3</i> corresponded to the GABA content and GAD activity. <i>DlGAD3</i> was localized in the cytoplasm, and its transient overexpression promoted an increase in the GABA content in <i>Nicotiana benthamiana</i> leaves. Overall, our results show that <i>DlGAD3</i> is able to promote the accumulation of GABA and may play a major role in its biosynthesis in longan pulp.
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