Transcriptome-based identification of AP2/ERF family genes and their cold-regulated expression during the dormancy phase transition of Chinese cherry flower buds

In Chinese cherry (Prunus pseudocerasus), a typical perennial deciduous fruit tree, flower bud dormancy is a crucial process that helps avoid cold-related injury in winter. A sufficient chill accumulation is the most important factor triggering bud dormancy break. However, the molecular mechanisms of dormancy release have not yet been determined. APETAL2/Ethylene Responsive Factor (AP2/ERF) is a large family of plant transcription factors that play significant roles in plant development and responses to various abiotic stresses, including low temperature. Nevertheless, little is known about the numbers, structural characteristics, molecular phylogenetics, and expression patterns of AP2/ERF genes in dormant cherry flower buds. Here, the PpcAP2/ERF gene family was investigated, and 68 genes were identified from dormant flower bud-derived transcriptome data. These PpcAP2/ERFs were divided into four subfamilies, with 16, 4, 46 and 1 members in PpcAP2, PpcRAV, PpcERF and Soloists, respectively. The amino acid composition of cherry PpcAP2/ERFs revealed common conservative residues and elements compared with Arabidopsis AP2/ERFs. High expression levels of several PpcAP2/ERF genes in dormant flower buds occurred in different dormancy stages, indicating that these genes are involved in flower bud dormancy transition. The expressed PpcAP2/ERF genes significantly enriched in gene ontology's biological processes were involved in hormone-signaling pathways and may regulate these pathways, which influences dormancy transition. A qRT-PCR analysis showed that 15 PpcAP2/ERF genes were strongly upregulated at 4 °C, indicating that PpcAP2/ERFs could be involved in the cold-mediated dormancy transition.