Aux/IAA proteins repress expression of reporter genes containing natural and highly active synthetic auxin response elements.

TLDR

A highly active synthetic auxin response element (DR5) was engineered by site‑directed mutagenesis of a natural composite AuxRE from the soybean GH3 promoter, producing tandem 11‑bp repeats that include the TGTCTC motif. DR5 showed greater auxin responsiveness than the natural AuxRE and GH3 promoter in transient carrot protoplasts and stable Arabidopsis seedlings, and its activity is specifically repressed by overexpressed Aux/IAA proteins while being bound by ARF1.

Abstract

A highly active synthetic auxin response element (AuxRE), referred to as DR5, was created by performing site-directed mutations in a natural composite AuxRE found in the soybean GH3 promoter. DR5 consisted of tandem direct repeats of 11 bp that included the auxin-responsive TGTCTC element. The DR5 AuxRE showed greater auxin responsiveness than a natural composite AuxRE and the GH3 promoter when assayed by transient expression in carrot protoplasts or in stably transformed Arabidopsis seedlings, and it provides a useful reporter gene for studying auxin-responsive transcription in wild-type plants and mutants. An auxin response transcription factor, ARF1, bound with specificity to the DR5 AuxRE in vitro and interacted with Aux/IAA proteins in a yeast two-hybrid system. Cotransfection experiments with natural and synthetic AuxRE reporter genes and effector genes encoding Aux/IAA proteins showed that overexpression of Aux/IAA proteins in carrot protoplasts resulted in specific repression of TGTCTC AuxRE reporter gene expression.