Potato tonoplast sugar transporter 1 controls tuber sugar accumulation during postharvest cold storage

Abstract

Cold-induced sweetening (CIS), the undesirable sugar accumulation in cold-stored potato (<i>Solanum tuberosum</i> L.) tubers, is a severe postharvest issue in the potato processing industry. Although the process of sucrose hydrolysis by vacuolar invertase during potato CIS is well understood, there is limited knowledge about the transportation of sucrose from the cytosol to the vacuole during postharvest cold storage. Here, we report that among the three potato tonoplast sugar transporters (TSTs), <i>StTST1</i> exhibits the highest expression in tubers during postharvest cold storage. Subcellular localization analysis demonstrates that StTST1 is a tonoplast-localized protein. S<i>tTST1</i> knockdown decreases reducing sugar accumulation in tubers during low-temperature storage. Compared to wild-type, potato chips produced from <i>StTST1</i>-silenced tubers displayed significantly lower acrylamide levels and lighter color after cold storage. Transcriptome analysis manifests that suppression of <i>StTST1</i> promotes starch synthesis and inhibits starch degradation in cold-stored tubers. We further establish that the increased sucrose content in the <i>StTST1</i>-silenced tubers might cause a decrease in the ABA content, thereby inhibiting the ABA-signaling pathway. We demonstrate that the down-regulation of β-amylase <i>StBAM1</i> in <i>StTST1</i>-silenced tubers might be directly controlled by ABA-responsive element-binding proteins (AREBs). Altogether, we have shown that <i>StTST1</i> plays a critical role in sugar accumulation and starch metabolism regulation during postharvest cold storage. Thus, our findings provide a new strategy to improve the frying quality of cold-stored tubers and reduce the acrylamide content in potato chips.