Genome-Wide Identification and Expression Analysis of Sucrose Phosphate Synthase, Sucrose Synthase, and Invertase in Carrot (Daucus carota L.)

Background: Carbon partitioning and energy supply in plants are largely dictated by sucrose metabolism, which is coordinately mediated by sucrose phosphate synthase (SPS), sucrose synthase (SUS), and invertase (INV). Carrot is an economically important root crop worldwide. As the major transport and storage disaccharide, sucrose modulates root osmotic potential and sweetness depending on its accumulation level. However, the genome-wide characteristics of the SPS, SUS, and INV gene families in carrot, as well as their expression dynamics across developmental stages and under stress conditions, remain unknown. Methods: In this study, we identified these gene families in carrot and characterized their phylogenetic relationships, gene structures, conserved protein motifs, chromosomal distribution, and expression profiles across developmental stages and under abiotic treatment with stress-inducing agents. Results: A total of 5 SPS, 8 SUS, and 19 INV genes were identified in carrot. Phylogenetic analysis revealed that members within the same subfamily share similar exon–intron structures and conserved motif compositions. Segment duplication, rather than tandem duplication, emerged as the primary driver of family expansion. Transcript profiling revealed that DcSPS, DcSUS, and DcINV paralogs exhibit varied spatiotemporal expression signatures across tissues and developmental stages, and several are robustly activated as fleshy roots expand. Upon abiotic challenge, these genes undergo differential transcriptional modulation, and many members show pronounced induction under NaCl or exogenous ABA treatment. Conclusions: Collectively, these findings provide a comprehensive inventory of the SPS, SUS, and INV gene families in carrot and generate testable hypotheses regarding their potential roles in sucrose metabolism. The identified genes and their expression profiles offer a valuable genetic resource for future functional studies and sucrose-based quality improvement in this crop.