The wheat transcription factor TaABF1 physically interacts with the protein kinase PKABA1 and mediates both abscisic acid (ABA)-induced and ABA-suppressed gene expression. In bombarded aleurone cells of imbibing grains, the effect of TaABF1 in down-regulating the gibberellin (GA)-induced promoter was stronger in the presence of exogenous ABA. As these grains contained low levels of endogenous ABA, the effect of TaABF1 may also be mediated by ABA-induced activation even in the absence of exogenous ABA. Levels of TaABF1 protein decreased slightly during imbibition of afterripened grains. However, TaABF1 levels (especially in aleurone layers) were not substantially affected by exogenous ABA or GA, indicating that changes in TaABF1 protein level are not an important part of regulating its role in hormone signalling. We found that TaABF1 was phosphorylated in aleurone cells, suggesting a role for post-translational modification in regulating TaABF1 activity. Induction of by overexpression of the transcription factor GAMyb could not be prevented by TaABF1, indicating that TaABF1 acts upstream of transcription in the signalling pathway. Supporting this view, knockdown of TaABF1 by RNA interference resulted in increased expression from the promoter. These results are consistent with a model in which TaABF1 is constitutively present in aleurone cells, while its ability to down-regulate is regulated in response to ABA.