Genome-Wide Identification of the Sulfate Transporter Gene Family Reveals That BolSULTR2;1 Regulates Plant Resistance to Alternaria brassicicola Through the Modulation of Glutathione Biosynthesis in Broccoli

Sulfate transporters (SULTRs) are key players that regulate sulfur acquisition and distribution within plants, thereby influencing cellular redox hemostasis under pathogen attacks, such as Alternaria brassicicola (Ab). In this study, a total of 23 BolSULTR (Brassica oleracea SULTR) genes were identified from the Brassica genome. These BolSULTRs are distributed across nine chromosomes, with all collinear BolSULTR gene pairs undergoing purifying selections. Phylogenetic analysis reveals that the SULTR family is evolutionarily conserved among plant kingdoms. qRT-PCR analysis demonstrated that the expression of BolSULTRs varies across different plant organs and is modulated by hormonal signals. Furthermore, transcriptome analysis identified several BolSULTRs whose expression levels were depressed in Ab-challenged leaves in broccoli. Among them, the BolSULTR2;1 gene emerged as a key player in the plant's response to Ab. Virus-induced gene silencing (VIGS) of BolSULTR2;1s resulted in elevated glutathione (GSH) levels and enhanced tolerance to Ab. Taken together, these findings underscore the role of BolSULTR2;1 in maintaining redox homeostasis and enhancing plant disease resistance, suggesting its potential as a target for genome editing to develop broccoli varieties with improved pathogen tolerance.