Integrative analysis of sulfate transporters in Citrus sinensis reveals CsSULTR3;5 involved in pathogen stress response

Selenium treatment has been shown to enhance plant resilience against both biotic and abiotic stresses; however, whether it can improve citrus resistance to bacterial diseases remains unexplored. In this study, we systematically identified sulfate transporter (Sultr) genes in the Citrus sinensis genome that are involved in selenate uptake. Analysis of gene structure, conserved motifs, and protein domains revealed a high degree of conservation among CsSultrs. Collinearity analysis between C. sinensis and Arabidopsis thaliana Sultr genes suggested possible evolutionary duplication and divergence events. Expression profiling of sulfur-related genes in C. sinensis following infection with Candidatus Liberibacter asiaticus, Xanthomonas citri subsp. citri, and Colletotrichum gloeosporioides showed that CsSULTR3;5 is responsive to pathogen infection. Subcellular localization indicated that CsSULTR3;5 is localized to the cell membrane and other intracellular organelles. Transient expression of CsSULTR3;5 in Nicotiana benthamiana did not affect leaf chlorophyll or carotenoid content. Furthermore, overexpression of CsSULTR3;5 enhanced resistance to citrus canker. These findings provide insight into the mechanisms by which selenium modulates biotic stress responses in citrus.