Genome-wide identification and expression analysis of the monosaccharide transporter (MST) gene family in wheat (Triticum aestivum L.)

Carbohydrates function as both energy sources and signaling molecules in various critical physiological processes. Monosaccharide transporters (MSTs) are a class of membrane-bound carrier proteins in crops that mediate the transmembrane transport of monosaccharides, thereby playing a central role in crop growth and development, resource allocation, and responses to environmental stimuli. In this study, a total of 200 MST family genes were identified in wheat and categorized into seven subfamilies. Twenty conserved motifs were detected within the TaMST family, with each subfamily exhibiting similar conserved motif patterns. The TaMST gene family was evenly distributed across the three wheat subgenomes, with both segmental and tandem duplications contributing to gene family expansion. The TaMST gene family was found to contain numerous cis-regulatory elements associated with growth and development, hormone signaling, and abiotic stress responses. Expression analysis revealed that most TaMSTs were expressed at low levels in wheat grains, whereas 69, 66, 67, and 64 genes exhibited high expression levels in leaves, buds, roots, and spikes, respectively. Following exogenous sugar treatments, the expression of all TaMSTs in roots was down-regulated, while 4, 2, and 3 genes showed up-regulated expression in leaves after treatment with fructose, glucose, and sucrose, respectively. Subcellular localization displayed TaERD3, TaPMT29 and TaSTP18 were all located on the cell membrane. These findings suggest that MSTs play essential roles not only in wheat organ development but also in the perception and response to sugar signaling. This study provides valuable insights for future investigations into the functional divergence of the MST gene family.