Embryos are oriented with anterior to the left. The mutated reporter contains 11 Bcd binding sites and no Zld sites. Results Bicoid target gene expression boundaries are influenced by other patterning factors, but its physical interaction with DNA targets is not To investigate the mechanism whereby Bcd functions to pattern the AP axis, we performed chromatin immunoprecipitation followed by high throughput sequencing ChIP-seq to determine the genome-wide binding profile of Bcd to its targets. For Bcd aficionados it may be easier, but for the more general audience of eLife , it might be difficult to read, not only because of the many typos, but the jargon and flow. B Expression of the wild-type and mutated reporter in wild-type, bcd — or zld — embryos.

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We replicated the previously reported result, that HC45 is inactive in blastoderm embryos, and that adding 4 Zld sites confers activity to the reporter. Measurement and perturbation of morphogen lifetime: In the absence of Zld binding, the wild-type enhancer does not drive expression Figure 6B and Figure 6—figure supplement 1A.

The mutated cad enhancer sequences were synthesized by GenScript, amplified using primers F primer: We will discuss experiment 3 first, followed by our dd at experiments 1 and 2.

The reporters expressed at stage 4—6 that overlapped 6.7 more than one Bcd peak were excluded from the plot in Figure 2B. While it is difficult to determine whether the homedomain structure is completely x in the GFP-Bcd construct, we tested the ability to the truncated protein to bind to Bcd target sequences compared to a wild-type GFP-Bcd protein. Namely, that Zld contributes to the accessibility of Bcd target genes throughout the embryo, while high levels of Bcd can drive accessibility independently and activate gene expression at a subset of targets in the anterior of the embryo.

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Isolation of mutations that disrupt cooperative DNA binding by the Drosophila bicoid protein. The acidic C domain has been demonstrated to play a role in transcriptional activation in yeast, but is not required for Bcd activity in the embryo Driever et al.


Nevertheless, please show the data that led to this conclusion that peaks “overall associate with enhancers…” The description of expression patterns that span broadly across the AP axis was meant to refer to the 66 previously identified Bcd-dependent enhancers that overlap with our ChIP-seq peaks.

The use of the word “enhancer” is vague and somewhat misleading. Also, why don’t all candidate enhancers overlap with a Bcd peak if the overlap with at least one Bcd peak. Transgenic flies containing the uBcd constructs were crossed into a bcd E1 background. Highly expressed loci are vulnerable to misleading ChIP localization of multiple unrelated proteins.

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In support of this, we find that chromatin accessibility at Bcd-dependent, concentration-sensitive targets is responsive to Bcd concentration. This may be a common property of developmental transcription factors that must gain early access to their target enhancers while the chromatin state of the genome is being remodeled during large-scale transitions in .607 gene regulatory landscape.

Of the 1, Bcd-bound regions identified by ChIP-seq, Unfortunately, when we performed the FAIRE experiment, the primers that effectively distinguish between the transgenic and endogenous cad enhancer in intact genomic DNA do not distinguish between the wild-type and transgenic alleles on a sheared DNA sample. Targeting gene expression to the head: However, in terms of Zld dependence, the more relevant feature is whether a peak is open or closed in the absence of Zld.

Though it is brave to conclude from the data presented that Bcd sensitivity class gene expression domains are not defined by repressors, it seems dangerous because so many AP gene domains that have been well studied are defined by repressor interactions. The data in Figure 2—figure supplement 1 suggest that while repressors interact with Bcd targets in each class, it is not clear from the binding 66.07 that these repressors 66.07 the concentration sensitivity of the Bcd ChIP classes.


These effects on the body plan indicate that the uniform Bcd transgenes can specify cell fates that reflect their relative expression levels. The Manufacturers disclaim all warranties including implied warranties of merchantability or fitness for a particular purpose and are not liable for any damages arising from your use of or your inability to use the Information downloaded from this website.

Concentration dependent chromatin states induced by the bicoid morphogen gradient

Author response image 2. The role of localization of bicoid RNA in organizing the anterior pattern of the Drosophila embryo. We considered the possibility that, given their influence on the expression domains of Bcd target genes, the posterior and terminal patterning systems may impact Bcd binding to its target enhancers in different nuclei along the AP axis. Establishment and maintenance of heritable chromatin structure during early Drosophila embryogenesis.

We thank the reviewers for pointing out the confusion that allowed us to detect and correct this error has been corrected in the manuscript.

Animal transcription networks as highly connected, quantitative continua. However, if the Bcd x are x into those bound and not bound by Zld, we do observe an enrichment of the Concentration-Insensitive peaks in Zld-dependent, Zld-bound peaks Figure 3—figure supplement 1. Therefore, although the expression domains of Bcd target genes are ultimately influenced by inputs from other AP patterning systems, the physical interaction of Bcd with DNA occurs independently of other maternal AP patterning inputs.

Error bars are standard error from 2 to 3 technical replicates per V probe. Alternately, when we replace Zld sites with Bcd sites in an enhancer that drives posterior expression, the expression domain shifts to the anterior of the embryo.