= DR5 auxin response element
{c}
The \b[DR5 auxin response element] is a synthetic regulatory <DNA> arrangement containing repeated <auxin response elements>. When used to control a <reporter gene>, it contributes the responsive regulatory part of a <DR5 auxin response reporter>. The DNA element and the measurable reporter product are different parts of that system.<Aux IAA proteins repress expression of reporter genes containing natural and highly active synthetic auxin response elements by T. Ulmasov and others>[Abstract, Plant Cell9 (1997), pp.1963–1971: synthetic tandem-repeat element and reporter comparisons.]{ref}
The original study compared DR5 with natural regulatory sequences and found strong <auxin>-responsive expression in the tested plant systems. It also connected binding by <auxin response factor 1> with regulatory effects involving <Aux IAA proteins>. This made DR5 useful for studying responsive <transcription>, rather than establishing a direct physical measurement of <auxin> concentration.<Aux IAA proteins repress expression of reporter genes containing natural and highly active synthetic auxin response elements by T. Ulmasov and others>[Abstract: response comparison, factor binding and repression.]{ref}
An illuminating experimental distinction is between asking whether a <protein> recognizes this DNA arrangement and asking whether a reporter is expressed in a particular <cell>. The first concerns molecular binding; the second also depends on the surrounding regulatory system and reporter behavior. A repeated regulatory element can therefore be a sensitive response tool without being a universal hormone-concentration scale.
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