The mining and evolutionary investigation of AP2/ERF genes in pear (Pyrus)

Background: In plants, ERF genes participate in a variety of regulatory pathways, such as plant growth and biotic and/or abiotic stress responses. Although the genome of Chinese white pear ('Dangshansuli') has been released, knowledge regarding the ERF family in pear, such as gene functions, evolutionary history and expression patterns, remains limited. Results: In our study, a total of 155 members of ERF families were identified in pear (Pyrus bretschneideri). The Ka and Ks values suggested that whole-genome duplication (WGD) and dispersed duplication have effectively contributed to the expansion of the pear ERF family. Gene structure and phylogeny analysis divided the PbrERF family into 12 groups, and their gene functions were predicted by comparative analysis. qRT-PCR was carried out to verify the relative expression levels of 7 genes in group III using wild and cultivated pear fruits at three key developmental stages. Wild samples had higher expression of these genes than cultivated samples, especially at the enlarged fruit stage. The transcriptome data of pear seedlings subjected to dehydration treatment further revealed that 4 of the 7 genes responded to drought conditions. Conclusion: The AP2/ERF gene family is greatly expanded in pear. Comparative analysis revealed the probability of ERF genes performing functional roles in multiple pathways. Expression analysis at different stages of pear fruit development in wild and cultivated samples indicated that genes in group III might be involved in abiotic and/or biotic stresses. Further transcriptome data on seedlings subjected to drought treatment verified the potential role of ERF genes in stress response. These results will provide a valuable reference for understanding the function and evolution of the ERF family in higher plants.