*4.2. Phylogenetic and Classification Analysis*

The phylogenetic tree of AP2 genes from *Rhododendron* and *Arabidopsis* was conducted using neighbor-joining method with 1000 bootstrap replications to show their evolutionary relationship with MEGA software (version 5.1) [43]. The phylogenetic tree was further modified with Evolview (https://www.evolgenius.info/evolview/#/treeview, accessed on 29 June 2022) [44]. The *Rhododendron* AP2 genes were classified into five subfamilies, AP2, ERF, DREB, RAV and soloist, depending on the number of AP2 domains and other features in sequence according to previous studies [45]. The ERF and DREB subfamilies were further classified into eleven subgroups according to the topology of phylogenetic tree and classification of the *Arabidopsis* AP2 gene family.
