THE TRIHELIX DNA-BINDING MOTIF IN HIGHER-PLANTS IS NOT RESTRICTED TO THE TRANSCRIPTION FACTORS GT-1 AND GT-2

GT-2 is a plant transcriptional activator that contains two separate, but similar, trihelix DNA-binding domains, GT-1 is similar to GT-2, al though it contains only one of such domains, cDNAs that encode GT-2 we re isolated from rice (OS-GT2) and Arabidopsis (AT-GT2), Evidence is p resented for the existence of an Arabidopsis gene family that is struc turally related to AT-GT2, Two members of this GT2-like family, AT-GTL 1 and AT-GTL2, have been isolated and characterized, Their sequences s uggest that they evolved by a recent gene duplication event, Both AT-G T2 and AT-GTL genes contain an intron in the amino-terminal trihelix m otif, indicating that this DNA-binding domain resulted from exon shuff ling, RNA gel blot analysis using AT-GTL1 as a probe revealed four tra nscripts in the aerial part of the plant. All mRNA levels were signifi cantly higher in siliques, suggesting that this gene family may functi on in fruit and/or seed development, To date, DNA-binding proteins cha racterized by the trihelix motif have been described only in plants, a nd may therefore be involved in plant-specific processes, Our results show that in Arabidopsis thaliana, the trihelix motif is not restricte d to the GT-1 and GT-2 DNA-binding proteins.