*2.1. Identification and Analysis of RsAP2 Genes*

A total of 120 AP2 genes were obtained through Hidden Markov Model (HMM) searches with the *Rhododendron*-specific AP2 model, and their AP2 domains were confirmed by the Simole Modular Architecture Research Tool (SMART), the National Center for Biotechnology Information Conserved Domains Database (NCBI CDD) and Pfam. The sequences were named according to their chromosomal location. Gene characteristics, including gene names, IDs, subfamilies, length of proteins, molecular weight of proteins (MW), isoelectric points (pI), chromosomal locations and main subcellular localizations are displayed in Table S1. Among all of the RsAP2 proteins, RsAP2-59 was identified as the largest protein with 906 aa and 100.7 kDa, while RsAP2-16 was the smallest, with 129 aa and 13.6 kDa in protein length and MW, respectively. The results of subcellular localization prediction showed that RsAP2 proteins were mainly located in the nucleus, followed by the chloroplast.
