Identification and Characterization of the Populus AREB/ABF Subfamily

Abscisic acid (ABA) is a major plant hormone that plays an important role in responses to abiotic stresses. The ABA-responsive element binding protein/ABRE-binding factor (AREB/ABF) gene subfamily contains crucial transcription factors in the ABA-mediated signaling pathway. In this study, a total of 14 putative AREB/ABF members were identified in the Populus trichocarpa Torr. & Gray. genome using five AREB/ABF amino acid sequences from Arabidopsis thaliana L. as probes. The 14 putative Populus subfamily members showed high protein similarities, especially in the basic leucine zipper (bZIP) domain region. A neighbor-joining analysis combined with gene structure data revealed homology among the 14 genes. The expression patterns of the Populus AREB/ABF subfamily suggested that the most abundant transcripts of 11 genes occurred in leaf tissues, while two genes were most transcribed in root tissues. Significantly, eight Populus AREB/ABF gene members were upregulated after treatment with 100 mu M exogenous ABA, while the other six members were downregulated. We identified the expression profiles of the subfamily members in Populus tissues and elucidated different response patterns of Populus AREB/ABF members to ABA stress. This study provided insight into the roles of Populus AREB/ABF homologues in plant response to abiotic stresses.