Tonoplast sugar transporter StTST1 mediates vacuolar sugar partitioning and abiotic stress tolerance in potato

Sugar transporters play pivotal roles in plant growth, development, and stress responses. However, the function of sugar transporters in potato (Solanum tuberosum) is still obscure. In this study, the function of potato tonoplast sugar transporter 1 (StTST1) in subcellular sugar compartmentation and abiotic stress tolerance was characterized. Heterologous expression assays in Saccharomyces cerevisiae (strain W303) demonstrated that StTST1 mediates sucrose transporting into the vacuole. Moreover overexpression and RNA interference (RNAi) of StTST1 in potato altered leafy sugar content including sucrose, glucose, and fructose without affecting the activity of key metabolic enzymes. Intriguingly, RNAi-mediated suppression of StTST1 enhanced freezing tolerance and compromised drought tolerance. In contrast, overexpression of StTST1 enhanced drought tolerance but reduced freezing tolerance. Our results demonstrate that StTST1 dynamically regulates subcellular sugar partitioning and differentially modulates freezing and drought stress responses. These findings highlight the potential of targeted manipulation of sugar transporters to modulate crop resilience to multiple abiotic stresses.