Protein-protein interactions among the Aux/IAA proteins.
The plant hormone indoleacetic acid (IAA) transcriptionally activates early genes in plants. The Aux/IAA family of early genes encodes proteins that are short-lived and nuclear-localized. They also contain a putative prokaryotic betaalphaalpha DNA binding motif whose formation requires protein dimerization. Here, we show that the pea PS-IAA4 and Arabidopsis IAA1 and IAA2 proteins perform homo- and heterotypic interactions in yeast using the two-hybrid system. Gel-filtration chromatography and chemical cross-linking experiments demonstrate that the PS-IAA4 and IAA1 proteins interact to form homodimers in vitro. Deletion analysis of PS-IAA4 indicates that the betaalphaalpha containing acidic C terminus of the protein is necessary for homotypic interactions in the yeast two-hybrid system. Screening an Arabidopsis lambda-ACT cDNA library using IAA1 as a bait reveals heterotypic interactions of IAA1 with known and newly discovered members of the Arabidopsis Aux/IAA gene family. The new member IAA24 has similarity to ARF1, a transcription factor that binds to an auxin response element. Combinatorial interactions among the various members of the Aux/IAA gene family may regulate a variety of late genes as well as serve as autoregulators of early auxin-regulated gene expression. These interactions provide a molecular basis for the developmental and tissue-specific manner of auxin action.
Kim
J
J
Plant Gene Expression Center, 800 Buchanan Street, Albany, CA 94710, USA.
Harter
K
K
Theologis
A
A
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D007210:Indoleacetic Acids / Q000378:metabolism*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D018532:Pisum sativum / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism*; D011485:Protein Binding; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors
D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; C491592:IAA1 protein, Arabidopsis; C109031:IAA1 protein, plant; C109032:IAA4 protein, Arabidopsis; D007210:Indoleacetic Acids; C111371:MONOPTEROS protein, Arabidopsis; D009687:Nuclear Proteins; D010940:Plant Proteins; D011994:Recombinant Proteins; D015534:Trans-Activators; D014157:Transcription Factors