PT  - JOURNAL ARTICLE
AU  - Justin Crocker
AU  - David L. Stern
TI  - Functional regulatory evolution outside of the minimal <em>even-skipped</em> stripe 2 enhancer
AID  - 10.1101/101311
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 101311
4099  - http://biorxiv.org/content/early/2017/01/18/101311.short
4100  - http://biorxiv.org/content/early/2017/01/18/101311.full
AB  - Transcriptional enhancers are regions of DNA that drive gene expression at precise times, levels, and locations. While many studies have elucidated how individual enhancers can evolve, most of this work has focused on what are called “minimal” enhancers, the smallest DNA regions that drive expression that approximates an aspect of native gene expression. Here we explore how the Drosophila erecta even-skipped (eve) locus has evolved by testing its activity in the divergent D. melanogaster genome. We found, as has been reported previously, that the minimal D. erecta eve stripe 2 enhancer (eveS2) fails to drive appreciable expression in D. melanogaster [1]. However, we found that a large transgene carrying the entire D. erecta eve locus drives normal eve expression, including in stripe 2. We performed a functional dissection of the region upstream of the D. erecta eveS2 region and found that regulatory information outside of the minimal D. erecta eveS2 contains multiple Zelda motifs that are required for normal expression. Our results illustrate how sequences outside of minimal enhancer regions can evolve functionally through mechanisms other than changes in transcription factor binding sites that drive patterning.