*2.2. Structures and Conserved Domains of Apple SAP Genes*

To gain insights into the structural diversity of SAP genes in apple, we analyzed the phylogenetic tree, exon–intron organization, and conserved domains in the coding sequences. The *MdSAP* proteins were classified as groups I and II based on their phylogenetic relationships (Figure 1A). Gene structure analysis indicated that *MdSAP1* through *MdSAP4*, *MdSAP6* through *MdSAP21*, *MdSAP23*, *MdSAP24*, *MdSAP26*, *MdSAP29*, and *MdSAP30* contained no introns, whereas *MdSAP5*, *MdSAP22*, *MdSAP25*, *MdSAP27*, and *MdSAP28* had one each (Figure 1B). Conserved domain analysis revealed that all of the *MdSAP* proteins included A20 and/or AN1 domain(s). *MdSAP1* through *MdSAP4*, *MdSAP7* through *MdSAP20*, *MdSAP23*, *MdSAP24*, *MdSAP26*, *MdSAP29*, and *MdSAP30* contained an A20 domain and an AN1 domain; *MdSAP5*, *MdSAP6*, and *MdSAP22* had single AN1 domains; and *MdSAP21*, *MdSAP25*, *MdSAP27*, and *MdSAP28* each had two AN1 domains. In addition, *MdSAP25* contained a C2H2 domain at the C terminal (Figures 1C and 2).

**Figure 1.** (**A**) Phylogenetic relationships; (**B**) Structures for 30 genes; and (**C**) Analysis of conserved domains for stress-associated protein (SAP) genes in apple. A phylogenetic tree for full-length amino acid sequences was constructed with MEGA software and the NJ method.



**Table 1.** Properties of SAPs identified from apple genome.

1

Gene ID in apple genome (https://www.rosaceae.org/gb/gbrowse/malus\_x\_domestica/).
