Genome-Wide Identification of the AP2/ERF Transcription Factor Family and Expression Analysis Under Selenium Stress in Cardamine hupingshanensis

AP2/ERF (APETALA2/ethylene-responsive factor) is one of the largest plant transcription factor families, characterized by 1-2 AP2/ERF domains (≈60–70 amino acids) that regulate plant development and biotic/abiotic stress responses. This study presents the first genome-wide identification and characterization of the AP2/ERF family in the selenium (Se) hyperaccumulator Cardamine hupingshanensis via bioinformatics. A total of 230 AP2/ERF genes were identified, which were non-randomly distributed across 16 chromosomes. Their encoded proteins varied in length (126–623 aa), molecular mass (13.927–68.112 kDa), and isoelectric point (4.48–10.31). Phylogenetic analysis classified these genes into five conserved subfamilies (AP2, DREB, ERF, RAV, Soloist), consistent with other plant species. Intron distribution differed among subfamilies (42.17% of genes contained introns), and motif 1 was universally conserved. Promoter cis-element analysis revealed enrichment of hormone-, stress-, and growth-related elements, highlighting potential roles in abiotic stress responses (notably, light and abscisic acid signaling). Expression profiling under Se stress (100 μg Se/L and 80,000 μg Se/L) demonstrated tissue-specific, dose-dependent, and temporal dynamic patterns. This inaugural genome-wide investigation of C. hupingshanensis AP2/ERFs provides foundational datasets for deciphering regulatory networks governing growth and Se stress response in this Se hyperaccumulator plant.