Genome-wide identification, analysis, and expression levels of honeysuckle APETALA2/ethylene-responsive factor gene family and functional analysis of the LjCBF1.13 gene in mediating abiotic stress resistance in Arabidopsis thaliana

The APETALA2/ethylene-responsive factor (AP2/ERF) superfamily plays a crucial role in plant growth at various developmental stages and in responses to external environmental stimuli. The yield and medicinal quality of honeysuckle ( Lonicera japonica Thunb.) are susceptible to the impacts of various environmental factors; however, this gene family remain uncharacterized in honeysuckle. In this study, the AP2/ERF proteins in honeysuckle (LjAP2/ERFs) were identified, and their properties and characteristics were investigated. A total of 181 LjAP2/ERF genes were screened and classified into five subfamilies. Chromosome distribution and homology analysis revealed that segment duplication is the key reason for the AP2/ERF family expansion in honeysuckle. Structure and motif analyses revealed that LjAP2/ERF proteins are relatively conserved. Moreover, LjAP2/ERF gene expression was analysed across multiple tissues and under abiotic stress conditions. The results indicate that LjERF2.4 plays a crucial role in honeysuckle tissue development at different stages, whereas LjCBF1.13 may serve as a key regulator of abiotic stress resistance in honeysuckle. Based on phenotypic, transcriptomic, metabolomic, and functional analyses of LjCBF1.13 in Arabidopsis thaliana , LjCBF1.13 is inferred to regulate hormonal response and signalling, thereby regulating plant tolerance to five abiotic stresses, including high temperature, low temperature, salt, and drought (mannitol and PEG6000). These findings provide a foundation for future research on the role of LjAP2/ERFs in protecting honeysuckle from environmental pressures and promoting growth and development.