Characterization of DREB family genes in loquat and their co-expression network analysis in response to drought

Loquat (Eriobotrya japonica Lindl.) is a popular fruit with a high medicinal value, and its growth is frequently affected by drought. The dehydration response element binding (DREB) transcription factor is one of the most promising regulators of plant tolerance to abiotic stresses, particularly drought. Genome-wide identification of the DREB family has been completed in numerous plant species, but not in loquat. In this study, 59 members of the EjDREB family were identified in loquat using genome-wide identification. These EjDREBs were classified into six subgroups (A1-A6) by phylogenetic analysis, and were found to be unevenly distributed on 12 chromosomes. In addition, these EjDREBs contained one AP2 or AP2 superfamily domain, and 88.14% EjDREBs were intronless. The main cis-acting elements in the EjDREB promoters were predicted to respond to transcription factors, environment factors, and hormones. Subcellular localization predictions signified that most EjDREBs were localized in the nucleus or both nucleus and cytoplasm. The expression pattern revealed that EjDREBs were expressed in various tissues and that their expression was induced by drought. After drought treatment, EjDREBs (EjDREB5.3, EjDREB5.6, EjDREB6.1, and EjDREB6.4) that were continuously expressed, as well as the differentially expressed EjDREBs (EjDREB2.3, EjDREB2.4, EjDREB3.2, EjDREB4.1, EjDREB4.4, EjDREB4.7, EjDREB4.14, EjDREB5.8, and EjDREB6.7) between drought-tolerant and drought-sensitive loquats may play important roles in the response to drought resistance. Furthermore, weighted gene co-expression network analysis (WGCNA) indicated that the genes co-expressed with EjDREBs were involved in the response to various adverse environments. Collectively, the EjDREB family genes of loquat were identified at the genome-wide level, and the gene expression patterns of EjDREBs were determined. Our results provide a basis for further investigations into the function of EjDREBs in the response of loquat to drought stress.