Genome-wide AP2/ERF gene family analysis reveals the classification, structure, expression profiles and potential function in orchardgrass (Dactylis glomerata)

The AP2/ERF transcription factor (TF) family is of great importance in developmental regulation and responses to stress and pathogenic stimuli. Orchardgrass (Dactylis glomerata), a perennial cold-season forage of high quality in the world's temperate zones, contributes to grazing land through mixed sowing with alfalfa (Medicago sativa) and white clover (Trifolium repens). However, little is known about AP2/ERF TFs in orchardgrass. In this study, 193 AP2/ERF genes were classified into five subfamilies and 13 subgroups through phylogenetic analysis. Chromosome structure analysis showed that AP2/ERF family genes in orchardgrass were distributed on seven chromosomes and specific conservative sequences were found in each subgroup. Exon-intron structure and motifs in the same subgroup were almost identical, and the unique motifs contributed to the classification and functional annotation of DgERFs. Expression analysis showed tissue-specific expression of DgERFs in roots and flowers, with most DgERFs widely expressed in roots. The expression levels of each subgroup (subgroups Vc, VIIa, VIIIb, IXa, and XIa) were high at the before-heading and heading stages (BH_DON and H_DON). In addition, 12 DgERFs in various tissues and five DgERFs associated with abiotic stresses were selected for qRT-PCR analysis showed that four dehydration-responsive element binding (DREB) genes and one ERF subfamily gene in orchardgrass were regulated with PEG, heat and salt stresses. DgERF056 belonged to ERF subfamily was involved in the processes of flowering and development stage. This study systematic explored the DgERFs at the genome level for the first time, which lays a foundation for a better understanding of AP2/ERF gene function in Dactylis glomerata and other types of forage.