ARF1, A TRANSCRIPTION FACTOR THAT BINDS TO AUXIN RESPONSE ELEMENTS

The plant hormone auxin regulates plant physiology by modulating the i nteraction of transcription factors with auxin response elements (AuxR Es) of the affected genes. A transcription factor, Auxin Response Fact or 1 (ARF1), that binds to the sequence TGTCTC in AuxREs was cloned fr om Arabidopsis by using a yeast one-hybrid system. ARF1 has an amino-t erminal DNA-binding domain related to the carboxyl terminus of the mai ze transactivator Viviparous-1. Sequence requirements for ARF1 binding in vitro are identical to those that confer auxin responsiveness in v ivo. The carboxyl terminus of ARF1 contains two motifs found in the Au x/IAA class of proteins and appears to mediate protein-protein interac tions.