Identification and characterization of the Quinoa AP2/ERF gene family and their expression patterns in response to salt stress.

The APETALA2/ETHYLENE RESPONSIVE FACTOR (AP2/ERF) transcription factors play crucial roles in plant growth, development, and responses to biotic and abiotic stresses. This study was performed to comprehensively identify and characterize the AP2/ERF gene family in quinoa (Chenopodium quinoa Willd.), a highly resilient pseudocereal crop known for its salinity tolerance. A total of 150 CqAP2/ERF genes were identified in the quinoa genome; these genes were unevenly distributed across the chromosomes. Phylogenetic analysis divided the CqAP2/ERFs into five subfamilies: 71 ERF, 49 DREB, 23 AP2, 3 RAV, and 4 Soloist. Additionally, the DREB and ERF subfamilies were subdivided into four and seven subgroups, respectively. The exon-intron structure of the putative CqAP2/ERF genes and the conserved motifs of their encoded proteins were also identified, showing general conservation within the phylogenetic subgroups. Promoter analysis revealed many cis-regulatory elements associated with light, hormones, and response mechanisms within the promoter regions of CqAP2/ERF genes. Synteny analysis revealed that segmental duplication under purifying selection pressure was the major evolutionary driver behind the expansion of the CqAP2/ERF gene family. The protein-protein interaction network predicted the pivotal CqAP2/ERF proteins and their interactions involved in the regulation of various biological processes including stress response mechanisms. The expression profiles obtained from RNA-seq and qRT-PCR data detected several salt-responsive CqAP2/ERF genes, particularly from the ERF, DREB, and RAV subfamilies, with varying up- and downregulation patterns, indicating their potential roles in salt stress responses in quinoa. Overall, this study provides insights into the structural and evolutionary features of the AP2/ERF gene family in quinoa, offering candidate genes for further analysis of their roles in salt tolerance and molecular breeding.