Identification and expression analysis of the AcSWEET gene family in Actinidia chinensis Planch.

The sugar will eventually be exported transporters (SWEET) are a recently discovered group of sugar transporters in plants, which play important roles in various physiological processes, such as plant growth, development, and abiotic and biotic stress. This study aimed to characterize the Actinidia chinensis Planch. SWEET gene family and analyze its expression during fruit development using bioinformatics methods. A total of 29 AcSWEET genes were identified, and their amino acid quantity, relative molecular weights, isoelectric points, instability coefficients, subcellular localizations, and hydrophilicity indices were analyzed. Results showed that the 29 AcSWEET genes encoded proteins with amino acid lengths ranging from 680 to 906 residues, molecular weights between 7.531 kDa and 101.266 kDa, and isoelectric points between 6.95 and 9.9. Most proteins were relatively stable hydrophobic, and localized on the cell membrane, containing 1–2 MtN3 domains. Additionally, gene structure, conserved motifs, evolutionary relationships, cis-regulatory elements, and expression patterns at different developmental stages of fruit development were systematically analyzed. Results indicated that the AcSWEET genes had 4–6 exons. Phylogenetic analysis revealed that the kiwifruit SWEET gene family was divided into four subgroups, responsible for transporting glucose, fructose, and sucrose. Genes within the same subgroup shared similar intron-exon structures and conserved motifs. Expression pattern analysis during kiwifruit development indicated that the AcSWEET genes exhibited stage-specific expression. We speculated that AcSWEET26, AcSWEET7, AcSWEET15, and AcSWEET13 may be involved in sucrose transport and accumulation in kiwifruit.