*Article* **Genome-Wide Identification of the Rose** *SWEET* **Gene Family and Their Different Expression Profiles in Cold Response between Two Rose Species**

**Xiangshang Song, Yaping Kou, Mingao Duan, Bo Feng, Xiaoyun Yu, Ruidong Jia, Xin Zhao, Hong Ge \* and Shuhua Yang \***

> State Key Laboratory of Vegetable Biobreeding, Key Laboratory of Biology and Genetic Improvement of Flower Crops (North China), Ministry of Agriculture and Rural Affairs, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China; fengb1107@163.com (B.F.)

**\*** Correspondence: gehong@caas.cn (H.G.); yangshuhua@caas.cn (S.Y.); Tel.: +86-10-8210-9542 (S.Y.)

**Abstract:** Sugars Will Eventually be Exported Transporter (SWEET) gene family plays indispensable roles in plant physiological activities, development processes, and responses to biotic and abiotic stresses, but no information is known for roses. In this study, a total of 25 *RcSWEET* genes were identified in *Rosa chinensis* 'Old Blush' by genome-wide analysis and clustered into four subgroups based on their phylogenetic relationships. The genomic features, including gene structures, conserved motifs, and gene duplication among the chromosomes of *RcSWEET* genes, were characterized. Seventeen types of *cis*-acting elements among the *RcSWEET* genes were predicted to exhibit their potential regulatory roles during biotic and abiotic stress and hormone responses. Tissue-specific and cold-response expression profiles based on transcriptome data showed that *SWEETs* play widely varying roles in development and stress tolerance in two rose species. Moreover, the different expression patterns of cold-response *SWEET* genes were verified by qRT-PCR between the moderately cold-resistant species *R. chinensis* 'Old Blush' and the extremely cold-resistant species *R. beggeriana*. Especially, *SWEET2a* and *SWEET10c* exhibited species differences after cold treatment and were sharply upregulated in the leaves of *R. beggeriana* but not *R. chinensis* 'Old Blush', indicating that these two genes may be the crucial candidates that participate in cold tolerance in *R. beggeriana*. Our results provide the foundation for function analysis of the *SWEET* gene family in roses, and will contribute to the breeding of cold-tolerant varieties of roses.

**Keywords:** rose; *SWEET* gene family; sugar transport; gene expression; cold response
