Genome-wide identification and expression analysis of the SWEET gene family in sweet sorghum (Sorghum dochna) and the role of SdSWEET01 in sugar transport

The SWEET sugar transporter plays a fundamental role in plant growth and development. In this study, 18 SWEET genes were identified from sweet sorghum (Sorghum dochna), encoding proteins with 231–336 amino acids, molecular weights from 25.15 to 35.69 kDa, and isoelectric points ranging between 6.41 and 9.69. Phylogenetic analysis categorized these proteins into four distinct subgroups. Examination of spatial expression patterns demonstrated that SdSWEET genes were expressed in a tissue-specific manner. Furthermore, their involvement in responses to various abiotic stresses, including cold, heat, drought, and salinity was observed. A yeast complementation assay verified that SdSWEET01, located on the plasma membrane, selectively transported glucose, sucrose, and galactose, while excluding fructose. Transgenic Arabidopsis expressing SdSWEET01 exhibited enhanced sugar absorption compared to wild-type plants, resulting in increased sensitivity and growth inhibition under high-sugar conditions. The study provides a detailed functional characterization of SdSWEET genes and emphasizes the critical role of SdSWEET01 in regulating sugar transport.