*4.7. RNA-Seq Data Analysis of RsAP2 Genes*

RNA-seq data were obtained from a previous study using *Rhododendron* cultivar 'Yanzhi Mi' flowers at 5 different developmental stages, including closed buds (S1), buds showing color at the top but with scales still present (S2), initial flowering stage (S3), full flowering stage (S4) and last flowering stage (S5), to analyze the expression patterns of RsAP2 genes during the flower development process (PRJNA700000) [52]. We created a local BLAST database with the Unigenes in the RNA-seq data and processed the tblastn search program with the RsAP2 protein sequence using BioEdit software (version 7.2.5). The corresponding relations were confirmed for the match of query–subject pairs with the lowest E-value, less than 1 × <sup>10</sup>−50. We used TBtools (version 1.098774) to construct the heatmap with the FPKM values transformed by log2. The RsAP2 protein interaction network was constructed by STRING (https://cn.string-db.org/, accessed on 4 January 2023) with the reference organism of *A. thaliana.*
