Genome-wide analysis of the AP2/ERF gene family in Salix arbutifolia

AP2/ERF genes encode transcriptional regulators with a variety of functions in plant growth and development and in response to biotic and abiotic stresses. To date, there are no detailed classification and expression profiles for AP2/ERF genes in Salix. In this study, a comprehensive computational analysis identified 173 AP2/ERF superfamily genes in willow (Salix arbutifolia), by using in silico cloning methods with the use of the AP2/ERF conserved domain amino acid sequence of Arabidopsis thaliana as a probe. Based on the results of phylogenetic analyses and the number of AP2/ERF domains, the AP2/ERF genes were classified into four groups: AP2, RAV, ERF and Soloist. The expression profile was analyzed using transcriptome data from different tissues. A comparative analysis of AP2/ERF superfamily genes among Salix, Populus and Arabidopsis was performed. The Salix DREB, AP2 and RAV groups had a similar number to those in Arabidopsis, and the size of the ERF subfamily in Salix was about 1.4-fold that of Arabidopsis. The Salix DREB subfamily was smaller compared to Populus, while the other families were similar in size to those in Populus. These results will be useful for future functional analyses of the ERF family genes.