**5. Conclusions**

This research focused on the analysis of *Rhododendron* AP2/ERF gene family. A total of 120 AP2/ERF genes were identified and their structural features described. The genes were classified into five subfamilies according to their domain and sequence structural characteristics. The phylogenetic comparison of AP2/ERF genes from *Arabidopsis* provided a valuable reference for the evolutionary characteristics of *Rhododendron* AP2/ERF genes. Many of the RsAP2 genes may participate in the development of *Rhododendron* and could be response factors to abiotic stress, such as cold, salt and drought. The expression patterns in different developmental stages and under different abiotic stress treatments indicated the different functions of RsAP2 members. This research generated relatively comprehensive information on the RsAP2 gene family and provides a theoretical basis for future further validation of RsAP2 gene function and protein interaction.

**Supplementary Materials:** The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/plants12050994/s1, Figure S1: Interaction network of RsAP2 protein referring to orthologs in *Arabidopsis*. Table S1: Features of RsAP2. Table S2: Cis-acting elements of RsAP2 promoters.

**Author Contributions:** Conceptualization, L.H. and Z.G.; methodology, X.S.; software, Z.G.; validation, C.L., X.L. and J.S.; formal analysis, Z.G.; resources, H.Z.; data curation, Z.G. and X.S.; writing—original draft preparation, Z.G.; writing—review and editing, L.H. and C.L.; visualization, Z.G.; supervision, H.Z.; project administration, X.L.; funding acquisition, J.S. and L.H. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the 'JBGS' Project of Seed Industry Revitalization in Jiangsu Province (JBGS(2021)095); Special Fund for Jiangsu Provincial Forestry Innovation and Promotion (LYKJ(2021)06); Special Fund for Forestry Development of Jiangsu Province (sczh (2022) No. 18); Jiangsu Agricultural industrial Technology system construction project (JATS(2022)101); Jiangsu Provincial Agricultural Science and Technology Innovation Project (CX (22)3061); the Central Financial Services Demonstration Funds for Forestry Science and Technology Promotion Project (Su (2021) TG06).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data are contained within the article and Supplementary Materials.

**Acknowledgments:** The authors gratefully acknowledge the financial support provided by the Natural Science Foundation of Jiangsu Province. We are thankful for the support provided by Jiangsu Academy of Agricultural Sciences.

**Conflicts of Interest:** The authors declare no conflict of interest.
