Transcriptome Reversal in Sulfate Transporter Involves Abiotic Stress in Sesuvium portulacastrum L

Sulfur is an essential nutrient involved in plant growth, redox regulation, and responses to environmental stresses. Sulfate transporters (SULTRs) control sulfate uptake and distribution, thereby affecting sulfur availability for metabolic processes and stress adaptation. However, the characteristics and stress-responsive functions of SULTRs in the halophyte Sesuvium portulacastrum remain unclear. In this study, we identified and characterized the SULTR family in S. portulacastrum through phylogenetic analysis, gene structure comparison, conserved motif analysis, promoter characterization, synteny analysis, and expression profiling. A total of 22 SpSULTRs were identified and classified into three subfamilies. Most SpSULTRs contained conserved Sulfate_transp and STAS domains and were predicted to localize to the plasma membrane. Transcriptome analysis combined with qRT-PCR validation revealed that SpSULTRs displayed diverse tissue-specific expression patterns under salt, cadmium, and copper stresses. Of these, SpSULTR3;1 and SpSULTR3;2 showed strong responses to salt stress and were mainly expressed in leaves. Protein interaction predictions suggested that these two transporters may be associated with sulfur assimilation, antioxidant metabolism, and stress-related pathways. These results reveal the structural diversification and stress-responsive characteristics of the SULTR family in S. portulacastrum and provide a basis for further investigation of sulfur transport mechanisms underlying halophyte adaptation.