Genome-Wide Identification and Expression Profiling of Plasma Membrane-Localized SWEET Gene Family Associated with Sugar Transport During Yam Tuber Development

This study provides the first comprehensive genome-wide identification and characterization of the <i>SWEET</i> gene family in yam (<i>Dioscorea rotundata</i>), integrating structural bioinformatics, gene expression profiling, and functional validation to explore its roles in sucrose transport and tuber development. A total of 19 <i>SWEET</i> genes were identified and predicted to localize to the plasma membrane, and they showed high phylogenetic conservation with <i>Arabidopsis thaliana</i>, suggesting conserved functions in sugar distribution. Yeast substrate assays revealed that <i>DrSWEET6</i> and <i>DrSWEET12</i> are capable of transporting both hexose and sucrose across the plasma membrane, with their expression predominantly observed in the tuber, implicating their involvement in sucrose unloading. Expression profiling indicated high expression levels of the <i>SWEET</i> genes at the tuber apex, which progressively increased during tuber development, underscoring their critical roles in sucrose unloading, cell expansion, and biomass accumulation. These findings provide novel insights into the structural and functional mechanisms of the SWEET-mediated sucrose transport in yam, laying a solid foundation for future crop improvement strategies aiming to optimize sucrose distribution and enhance tuber yield and quality.