Glutathione S-transferases (GSTs) play crucial roles in plant stress responses, particularly in salt stress acclimation, by participating in reactive oxygen species scavenging, detoxification, and regulation of hormone signaling. Avicennia marina , a pioneer mangrove species, exhibits long-term adaptation to extreme habitats such as high salinity, yet its GST gene family has not been systematically characterized. This study provides the first genome-wide characterization and identification of the GST gene family in A. marina , identifying 25 AmGST genes classified into five subfamilies: GSTU, GSTF, GSTT, EF1G and TCHQD. Evolutionary analysis indicated that AmGST s have undergone strong purifying selection. Gene structure and conserved motif analyses revealed subfamily-specific sequence patterns. Promoter analysis identified numerous cis -acting elements associated with stress responses and hormone regulation. Homology modeling and molecular docking predicted that three representative AmGST proteins, AmEF1G02, AmGSTF03 and AmGSTU08, can bind to glutathione (GSH) and indole-3-acetic acid (IAA) through multiple hydrogen bonds, suggesting their potential role in antioxidant defense and hormone modulation. Quantitative real-time PCR analysis showed distinct expression patterns of different AmGST s under salt treatment and exogenous auxin treatment. Notably, AmGSTF03 was consistently upregulated by salt and further enhanced by IAA, while the auxin-specific responsiveness of AmEF1G02 (strongly induced by IAA regardless of salinity) suggests its role as a potential crosstalk node between auxin signaling and detoxification pathways. AmGSTU08 exhibited early transient upregulation under salt and auxin, supporting its involvement in rapid stress responses. This study establishes that the A. marina GST family has been shaped by strong purifying selection and subfamily-specific structural divergence, highlighting the evolutionary conservation and functional diversity of AmGSTs . The potential dual binding ability of some protein members represented by AmEF1G02, AmGSTF03, and AmGSTU08 to GSH and IAA, as well as their different expression patterns, suggests that AmGSTs may serve as a molecular bridge connecting auxin signaling and antioxidant defense. These findings systematically reveal the composition, evolutionary features, and potential functions of the A. marina GST family in salinity stress and hormone regulation, providing new insights into the molecular mechanisms of salt tolerance in mangroves and candidate gene resources for improving crop salt tolerance.
Lin et al. (Mon,) studied this question.