Genome-wide investigation of the AP2/ERF superfamily and their expression under salt stress in Chinese willow ().

AP2/ERF transcription factors (TFs) play indispensable roles in plant growth, development, and especially in various abiotic stresses responses. The AP2/ERF TF family has been discovered and classified in more than 50 species. However, little is known about the gene family of Chinese willow (), which is a tetraploid ornamental tree species that is widely planted and is also considered as a species that can improve the soil salinity of coastal beaches. In this study, 364 genes of () were identified depending on the recently produced whole genome sequencing data of . These genes were renamed according to the chromosomal location of the genes. The genes included three major subfamilies: AP2 (55 members), ERF (301 members), and RAV (six members) and two Soloist genes. Genes' structure and conserved motifs were analyzed in SmAP2/ERF family members, and introns were not found in most genes of the ERF subfamily, some unique motifs were found to be important for the function of genes. Syntenic relationships between the genes and genes from and showed that is genetically more closely related to than to . Evolution analysis on paralog gene pairs suggested that progenitor of originated from hybridization between two different diploid salix germplasms and underwent genome duplication not more than 10 Mya. RNA sequencing results demonstrated the differential expression patterns of some genes under salt stress and this information can help reveal the mechanism of salt tolerance regulation in .