Identification, expression analysis, and functional characterization of salt stress‐responsive genes of AP2/ERF transcription factors in sweetpotato

Abstract The AP2/ERF transcription factors (TFs) regulate various processes of plant growth, development, and response to environmental stimuli. Although they have been extensively documented in many plants, little is known about stress responsive APETALA2/ethylene response factor (AP2/ERF) genes in sweetpotato ( Ipomoea batatas L.). In this study, 20 putative AP2/ERF genes, named IbERF1 , IbERF2 , and IbERF5–IbERF23 were identified based on the salt‐treated RNA‐seq data from two sweetpotato cultivars with different salt tolerance. Phylogenetic analysis and sequence characterization identified that all the screened IbERF proteins contained a conserved AP2 domain, which belonged to dehydration‐responsive element binding proteins (DREB; 7 members) or ERF (13 members) subfamily. The systematic expression analysis of 12 mainly salt‐induced IbERFs by quantitative real‐time polymerase chain reaction (qRT‐PCR) revealed that most IbERF s were remarkably increased by multiple abiotic stresses, such as NaCl, dehydration, and cold stress. Furthermore, varying degrees of upregulation were also detected in the expression of most IbERF s when treated with hormone abscisic acid, jasmonic acid, and salicylic acid. The expression profiles of IbERF s corroborate their involvement in diverse biological processes. In addition, the IbERF5, which was exclusively upregulated by the treatments, was identified as a nuclear protein without transcriptional activation activity. Collectively, the data of stress responsive IbERF s will provide valuable knowledge for further functional studies of IbERF s in sweetpotato stress tolerance.