= DR5 auxin response reporter
{c}
The \b[DR5 auxin response reporter] uses synthetic <auxin response elements> to control a <reporter gene>. Its output reports <auxin>-responsive <transcription>, rather than directly counting auxin molecules. DR5 is a regulatory DNA arrangement, not the name of an auxin-binding fluorescent molecule.<Aux IAA proteins repress expression of reporter genes containing natural and highly active synthetic auxin response elements by T. Ulmasov and others>[Abstract, Plant Cell 9 (1997), pp. 1963–1971; DOI 10.1105/tpc.9.11.1963.]{ref}
The original work compared DR5 with natural regulatory sequences in carrot cells and <Arabidopsis thaliana> seedlings. DR5 showed strong <auxin> responsiveness; a member of the <auxin response factor> family bound the element, while regulatory proteins could repress reporter expression. Those measurements tied the output to a transcriptional response system, rather than establishing a universal conversion from reporter intensity to hormone concentration.<Aux IAA proteins repress expression of reporter genes containing natural and highly active synthetic auxin response elements by T. Ulmasov and others>[Abstract: reporter comparison, factor binding and repression experiments.]{ref}
A useful example comes from <haustorium> development in <Phtheirospermum japonicum>. DR5 expression marked a localized response near the developing organ, while separate measurements of <indole-3-acetic acid> tested the interpretation that hormone levels rose there. The two observations support different claims: reporter output locates a response, and chemical measurement measures the hormone. Neither should silently substitute for the other.<Local Auxin Biosynthesis Mediated by a YUCCA Flavin Monooxygenase Regulates Haustorium Development in the Parasitic Plant Phtheirospermum japonicum by Juliane K. Ishida and others>[Results and Discussion: DR5 spatial response and independent IAA measurement near haustorium-forming sites.]{ref}
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