Genomic identification of AP2/ERF transcription factors and functional characterization of two cold resistance-related AP2/ERF genes in celery (Apium graveolens L.)

Main conclusion This study analyzed the AP2/ERF transcription factors in celery and showed that two dehydration-responsive-element-binding (DREB) transcription factors, AgDREB1 and AgDREB2, contribute to the enhanced resistance to abiotic stress in transgenic Arabidopsis. The AP2/ERF family is a large family of transcription factors (TFs) in higher plants that plays a central role in plant growth, development, and response to environmental stress. Here, 209 AP2/ERF family members were identified in celery based on genomic and transcriptomic data. The TFs were classified into four subfamilies (i.e., DREB, ERF, RAV, and AP2) and Soloist. Evolution analysis indicated that the AP2/ERF TFs are ancient molecules and have expanded in the long-term evolution process of plants and whole-genome duplication events. AgAP2/ERF proteins may be associated with multiple biological processes as predicted by the interaction network. The expression profiles and sequence alignment analysis of the TFs in the DREB-A1 group showed that eight genes could be divided into four branches. Two genes, AgDREB1 and AgDREB2, from the DREB-A1 group were selected for further analysis. Subcellular localization assay suggested that the two proteins are nuclear proteins. Yeast one hybrid assay demonstrated that the two proteins could bind to the dehydration-responsive element (DRE). The overexpression of AgDREB1 and AgDREB2 in Arabidopsis induced the increased tolerance to cold treatment and the up-regulation of the COR genes expression. AgDREB1 and AgDREB2 might function as transcriptional activators in regulating the downstream genes by binding to corresponding DRE to enhance stress tolerance in celery.