Genome-wide identification and analysis of auxin response factors in peels of wax apple at different fruit development stages

In this study, we used transcriptomic data to screen the auxin response factor gene family in the peels of wax apple at different stages of fruit development, in which fourteen auxin response factor genes (SsARFs) were identified and analyzed. The results showed that the 14 SsARFs were hydrophilic proteins located in the nucleus, with a higher ratio of serine and leucine, and a lower ratio of cysteine and tryptophan. These SsARF proteins consisted of irregularly coiled, extended strands, alpha-helices and beta-turns, most of which contained a B3 DNA-binding domain (B3-DBD), a middle region (MR) and a C-terminal dimerization domain (CTD), whereas some of them lacked a CTD, including SsARF6b, SsARF16, SsARF17, SsARF18 and SsARF22. Phylogenetic tree analysis revealed that the SsARFs were classified into five clusters. The expression of seven SsARFs were up-regulated, while the others were down-regulated. The protein interaction network of SsARFs showed strong interactions among SsARF4, SsARF5, SsARF6a, SsARF6b, SsARF17, SsARF19a, and SsARF19b, which interacted strongly with IAA12, IAA14 and IAA17. Therefore, SsARF6a, SsARF6b, SsARF17, SsARF19a, and SsARF19b, may play an important role in the auxin signal transduction pathway during wax apple fruit development.