GT factors constitute a plant-specific transcription factor family with a DNA-binding domain that binds GT elements. The DNA-binding domain of GT factor, rich in basic and acidic amino acids and proline and glutamine residues, features a typical trihelix (helix-loop-helix-loop-helix) structure that determines the specific binding of GT elements; thus GT factors are also called trihelix transcription factors. GT elements are highly degenerate cis-elements with A/T-rich core sequences (Villain et al. 1996; Wang et al. 2004). Interaction between GT factors and GT elements has been implicated in the complex transcriptional regulation of many plant genes.
