Sugar Transporter, CmSWEET17, Promotes Bud Outgrowth in Chrysanthemum Morifolium

We previously demonstrated that 20 mM sucrose promotes the upper axillary bud outgrowth in two-node stems of Chrysanthemum morifolium. In this study, we aimed to screen for potential genes involved in this process. Quantitative reverse transcription (qRT)-PCR analysis of sugar-related genes in the upper axillary bud of plants treated with 20 mM sucrose revealed the specific expression of the gene CmSWEET17. Expression of this gene was increased in the bud, as well as the leaves of C. morifolium, following exogenous sucrose treatment. CmSWEET17 was isolated from C. morifolium and a subcellular localization assay confirmed that the protein product was localized in the cell membrane. Overexpression of CmSWEET17 promoted upper axillary bud growth in the two-node stems treatment as compared with the wild-type. In addition, the expression of auxin transporter genes CmAUX1, CmLAX2, CmPIN1, CmPIN2, and CmPIN4 was upregulated in the upper axillary bud of CmSWEET17 overexpression lines, while indole-3-acetic acid content decreased. The results suggest that CmSWEET17 could be involved in the process of sucrose-induced axillary bud outgrowth in C. morifolium, possibly via the auxin transport pathway.