Insight into the sulfate transporter gene family in Nicotiana tabacum and functional analysis of NtSULTR1;3 in response to salt stress

Sulfate transporters (SULTRs) are crucial for sulfur uptake, distribution and stress adaptation in plants. Although SULTR families have been characterized in numerous species, this gene family remains uncharacterized in Nicotiana tabacum (tobacco), an allotetraploid species and an important economic crop within the Solanaceae family. A total of 32 NtSULTR genes were identified and classified into four subfamilies based on phylogenetic analysis. Expression profiling revealed that NtSULTR1;3 and NtSULTR1;4 were root-preferential and markedly down-regulated under salt stress. CRISPR/Cas9 knockout mutants of NtSULTR1;3 conferred enhanced root growth under normal conditions but extreme salt hypersensitivity. Crucially, sulfate (SO 4 2− ) content assays revealed significantly reduced SO 4 2− levels in mutant roots, directly linking the loss of NtSULTR1;3 to disrupted sulfate allocation. This study demonstrated that NtSULTR1;3 is essential for salt tolerance by maintaining sulfate homeostasis. Our findings provided the first comprehensive genomic identification and foundational characterization of the SULTR family in tobacco, underscoring the potential of NtSULTR1;3 as a target for improving stress resilience in crops.