Comprehensive Characterization of BrSULTRs Family and Their Expression Profiles Under Salt and Low-Temperature...

Sulfate transporters (SULTRs) are integral membrane proteins responsible for sulfate uptake, translocation, and plant adaptation to abiotic stresses. However, knowledge regarding the SULTR gene family in the economically important crop, Brassica rapa (Chinese cabbage), limited. The aim of this study is to conduct a genome-wide identification and functional characterization of BrSULTR genes and to explore their potential functions under abiotic stress.

We identified 19 BrSULTR genes in the B. rapa genome by performing homology searches with Arabidopsis thaliana SULTR sequences as queries. Subsequent bioinformatics analysis included phylogenetic classification, chromosomal localization, gene structure, conserved motif dissection, cis-regulatory element prediction, and protein-protein interaction (PPI) network analysis. Tissue-specific expression profiles of BrSULTRs were assessed using publicly available transcriptome data. Furthermore, their expression dynamics under salt (150 mM NaCl) and low-temperature (4 °C) stress were investigated by integrating transcriptomic, proteomic, and qRT-PCR data.

The 19 identified BrSULTR members were phylogenetically categorized into four subfamilies and were mapped unevenly across seven chromosomes. Promoter analysis identified an array of cis-regulatory elements associated with development, hormone response, and stress response. Expression profiles revealed distinct tissue-specific patterns in roots, stems, leaves, flowers, and siliques. Under salt stress, BrSULTR13 was significantly upregulated, while BrSULTR9 and BrSULTR11 were significantly suppressed under low-temperature stress. PPI network projection indicated that the Arabidopsis homologs of BrSULTR5 may physically interact with stress-regulating enzymes such as APS and APR.

Our work presents a comprehensive genomic and functional overview of the BrSULTR gene family in B. rapa. The results underscore the potential functions of BrSULTRs, highlighting their involvement in sulfate transport and abiotic stress responses. These insights establish valuable insights and a foundation for further research aiming at improving stress tolerance in B. rapa through the manipulation of sulfur metabolism pathways.