Large-scale genomic analysis reveals the origin and evolution of Glutathione S-transferases (GSTs) in plants

BACKGROUND: Glutathione S-transferases (GSTs) are a crucial gene superfamily for plant stress adaptation. However, their evolutionary trajectories and genomic organizational principles across the plant kingdom remain poorly understood. RESULTS: Through a large-scale comparative genomic analysis of 74 plant species, we identified 4,355 GST genes and classified them into 16 subfamilies. Phylogenetic reconstruction revealed massive and lineage-specific expansion of the stress-responsive Tau and Phi subfamilies in land plants, in contrast to the high conservation of ancient subfamilies (e.g., Theta, Zeta). Structural analysis suggested clade-specific motifs in Tau members associated with functional diversification. In polyploid barnyardgrass, genome duplication led to a disproportionate increase in GST copies: Tau and Phi genes showed unbalanced retention and formed selective clusters on homeologous group 1 and 2 chromosomes, while ancient subfamilies maintained dosage stability. CONCLUSIONS: Our study elucidates divergent evolutionary dynamics within the GST family. The lineage-specific expansion and selective retention of clustered Tau/Phi genes during polyploidization suggest a potential genomic signature that may be associated with adaptive evolution in plants. This study provides a comprehensive genomic resource and framework for future functional studies of GSTs in plant stress biology.