Genome-Wide Characterization, Comparative Analysis, and Expression Profiling of SWEET Genes Family in Four Cymbidium Species (Orchidaceae)

The SWEET (Sugar Will Eventually be Exported Transporters) protein family plays a key role in plant growth, adaptation, and stress responses by facilitating soluble sugar transport. However, their functions in <i>Cymbidium</i> remain poorly understood. This study identified 59 <i>SWEET</i> genes across four <i>Cymbidium</i> species, encoding conserved MtN3/saliva domains. Despite variations in exon-intron structures, gene motifs and domains were highly conserved. Phylogenetic analysis grouped 95 SWEET proteins from six species into four clades, with gene expansion driven by whole-genome, segmental, and tandem duplications. Cis-element analysis and expression profiling across 72 samples revealed diverse regulatory patterns. Notably, <i>SWEET</i> genes showed peak expression in floral development, leaf morph variations, and diurnal rhythms. qRT-PCR and transcription factor binding analysis further highlighted their regulatory roles in floral patterning, leaf variation, and metabolic rhythms. These findings provide a foundation for future studies on <i>SWEET</i> gene function and their potential molecular breeding value in orchids.