Genome-wide identification of the TGD2 gene family in seven plant species and functional characterization of soybean GmTGD2.1 in cold tolerance

Trigalactosyldiacylglycerol 2 ( TGD2 ) gene family plays a vital role in plant lipid metabolism and cold stress responses. TGD2 proteins mediate lipid transport from the endoplasmic reticulum (ER) to chloroplasts, which promotes the synthesis of specific galactolipids in thylakoid membranes and maintains membrane fluidity and stability under cold stress. In this study, a total of 26 TGD2 family members were identified from 7 plant species via genome-wide homology search. Phylogenetic analysis, conserved domain identification, chromosomal localization, and promoter cis-acting element analysis were systematically performed. Expression analysis showed that the soybean GmTGD2.1 gene was highly expressed in leaves and significantly upregulated under cold stress. Heterologous expression in transgenic Arabidopsis thaliana and yeast further verified that GmTGD2.1 overexpression enhanced plant low-temperature tolerance, reduced reactive oxygen species (ROS) accumulation, and inhibited membrane lipid peroxidation. This study systematically clarifies the structural and expression characteristics of the TGD2 gene family, laying a theoretical foundation for understanding the function of TGD2 genes in plant cold adaptation.