AP2/ERF transcription factors in plant stress adaptation: evolutionary expansion, functional diversification and hormone crosstalk.

APETALA2/ethylene response factor (AP2/ERF) transcription factors constitute a plant-specific regulatory family that coordinates plant development, environmental stress responses, and hormone signaling. However, the contribution of AP2/ERF family expansion and functional diversification to environmental adaptation has not been fully integrated across evolutionary and mechanistic scales. This review synthesizes classical findings and representative advances from the past five years in structural classification, duplication-driven expansion, functional diversification, stress adaptation, and hormone crosstalk, with particular emphasis on how post-duplication divergence shapes regulatory function. Across these studies, AP2/ERF proteins emerge as context-dependent nodes that connect environmental or hormonal signals with direct target genes and downstream physiological responses. This perspective distinguishes family expansion from demonstrated adaptive function and helps explain why closely related AP2/ERFs can produce contrasting outcomes in different biological contexts. We further discuss priorities for functional validation in non-model species, multi-stress experiments, multi-omics integration, field phenotyping, and gene-editing-based breeding, highlighting AP2/ERF regulators with potential for engineering stress-resilient crops.