ERF111/ABR1: An AP2 Domain Transcription Factor Serving as a Hub for Multiple Signaling Pathways

Plants can sustain under adverse conditions despite being sessile because of the presence of intricate and sophisticated signaling systems. All the perceived adverse stimuli can activate the signaling pathways, transducing the signals downstream, and bringing about an adaptive response. At the forefront of stress-mediated signaling pathways, transcription factors (TFs) are targeted by the signaling pathways to regulate the gene expression of the respective gene or set of genes. The AP2/ERF superfamily of TFs is important as they can regulate a plethora of plant physiological and developmental responses. This superfamily has four families named AP2, ERF, RAV, and Soloist. The entire superfamily modulates diverse plant responses ranging from development to stress physiology. We briefly discuss our current understanding of this family’s function in modulating a large number of plant physiological responses. One of the important members of this family is ABA REPRESSOR 1 (ABR1, aka ERF111). In this review, we trace and explore the history of ERF111/ABR1 and discuss the protein function—as a transcriptional activator and repressor. Different proteins can modulate ERF111/ABR1, either by binding to its promoter or by affecting it post translationally. ERF111/ABR1 can also modulate plant responses by regulating gene expression. ERF111/ABR1 can connect multiple signaling pathways as it seems to be at the nodal point where several hormonal pathways converge. We have also attempted to explore its possible role as a crosstalk hub and discuss the possible pathways it might regulate as a transcriptional on/off switch.