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ARS Home » Plains Area » Fargo, North Dakota » Edward T. Schafer Agricultural Research Center » Sugarbeet Research » Research » Publications at this Location » Publication #425352
Research Project: Improving Sugarbeet Productivity and Sustainability through Genetic, Genomic, Physiological, and Phytopathological Approaches

Location: Sugarbeet Research

Title: Genome-wide analysis of SWEET and TST sugar transporters in sugarbeet: Structural characterization and expression during development and postharvest storage

Author
item FUGATE, KAREN - Beet Sugar Development Foundation
item FINGER, FERNANDO - North Dakota State University
item Bolton, Melvin

Submitted to: Plant Gene
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/10/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Sugar transporters are proteins that permit simple sugars such as sucrose, glucose, and fructose to pass across cellular membranes. The importance of these proteins cannot be overstated since sugar transporters provide the impetus for the movement of sugar from photosynthetically active leaves to non-photosynthetic organs such as roots that depend on imported sugar to fuel their growth and development. Sugar transporters additionally mediate sugar movement between cells of plant organs and make sugar accumulation possible by sequestering them in intracellular compartments where they are separated from sucrose-degrading enzymes. Members of two sugar transporter families that are likely contributors to sugar accumulation during production and sucrose loss during storage were identified and characterized in sugarbeet, and included 16 SWEET (Sugars Will Eventually be Exported Transporter) transporters and four TST (Tonoplast Sugar Transporter) transporters. Of these 20 transporters, two SWEET transporters and one TST transporter were identified as likely to be important in leaves and roots, respectively, during development. Additionally, four SWEET and one TST transporters were elevated during storage suggesting their possible importance for postharvest storage loss. Taken together, the identified genes are likely targets for future investigations into the role of sugar transporters in sugarbeet sucrose yield at harvest and after storage.

Technical Abstract: SWEET (Sugars Will Eventually be Exported Transporter) and TST (Tonoplast Sugar Transporter) genes are implicated in sucrose accumulation and sucrose loss during sugarbeet root production and postharvest storage, although information regarding their identities, structures and expression is limited. Research, therefore, was conducted to identify and structurally characterize sugarbeet SWEET and TST gene families and determine their organ-specific, developmental, and storage-related expression. Sixteen SWEET genes and four TST genes were found in the sugarbeet genome. SWEET genes were notably diverse in genomic and transcriptomic structure, yet shared similarities in protein motifs and structure, whilst TST genes were generally uniform in genomic, transcriptomic, and protein size and structure. Expression analysis revealed high expression of two SWEET genes (SWEET 1, SWEET12) in leaves, relatively low levels of SWEET gene expression in roots throughout all but the earliest stages of development, and a dramatic upregulation of four SWEET genes (SWEET1, SWEET12, SWEET14/N3, SWEET17b) during storage, including a greater than 17,000-fold increase in SWEET14/N3 expression. TST genes were expressed in all tissue types, with most TST expression derived from a single gene (TST2.1) which was highly expressed in roots, minimally expressed in leaves, and elevated in expression during root storage. Overall, these results point to the likely importance of SWEET1 and SWEET12 in leaves and TST2.1 in roots during development when sucrose is actively being accumulated and the likely importance of SWEET14/N3, and possibly SWEET1, SWEET12, SWEET17b, and TST2.1 during storage when vacuolar sequestered sucrose is remobilized and catabolized.