Genome-Wide Characterization, Comparative Analysis, and Expression Profiling of Genes Family in Four 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 remain poorly understood. This study identified 59 genes across four 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, 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 gene function and their potential molecular breeding value in orchids.