scholarly journals Bicoid gradient formation and function in the Drosophila pre-syncytial blastoderm

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Zehra Ali-Murthy ◽  
Thomas B Kornberg
Keyword(s):  
Gene Expression ◽  
Target Gene ◽  
Drosophila Embryo ◽  
Anterior Pole ◽  
Concentration Gradients ◽  
Nuclear Cycle ◽  
Gradient Formation ◽  
Technical Issues ◽  
And Function ◽  
Anterior Posterior

Bicoid (Bcd) protein distributes in a concentration gradient that organizes the anterior/posterior axis of the Drosophila embryo. It has been understood that bcd RNA is sequestered at the anterior pole during oogenesis, is not translated until fertilization, and produces a protein gradient that functions in the syncytial blastoderm after 9–10 nuclear divisions. However, technical issues limited the sensitivity of analysis of pre-syncytial blastoderm embryos and precluded studies of oocytes after stage 13. We developed methods to analyze stage 14 oocytes and pre-syncytial blastoderm embryos, and found that stage 14 oocytes make Bcd protein, that bcd RNA and Bcd protein distribute in matching concentration gradients in the interior of nuclear cycle 2–6 embryos, and that Bcd regulation of target gene expression is apparent at nuclear cycle 7, two cycles prior to syncytial blastoderm. We discuss the implications for the generation and function of the Bcd gradient.

scholarly journals The GAGA factor is required in the early Drosophila embryo not only for transcriptional regulation but also for nuclear division

Development ◽  
1996 ◽  
Vol 122 (4) ◽  
pp. 1113-1124 ◽  
Author(s):  
K.M. Bhat ◽  
G. Farkas ◽  
F. Karch ◽  
H. Gyurkovics ◽  
J. Gausz ◽  
...  
Keyword(s):  
Gene Expression ◽  
Chromatin Remodeling ◽  
In Vitro Transcription ◽  
Drosophila Embryo ◽  
Gaga Factor ◽  
Early Drosophila Embryo ◽  
Hypersensitive Sites ◽  
And Function ◽  
Stimulatory Factor

The GAGA protein of Drosophila was first identified as a stimulatory factor in in vitro transcription assays using the engrailed and Ultrabithorax promoters. Subsequent studies have suggested that the GAGA factor promotes transcription by blocking the repressive effects of histones; moreover, it has been shown to function in chromatin remodeling, acting together with other factors in the formation of nuclease hypersensitive sites in vitro. The GAGA factor is encoded by the Trithorax-like locus and in the studies reported here we have used the maternal effect allele Trl13C to examine the functions of the protein during embryogenesis. We find that GAGA is required for the proper expression of a variety of developmental loci that contain GAGA binding sites in their upstream regulatory regions. The observed disruptions in gene expression are consistent with those expected for a factor involved in chromatin remodeling. In addition to facilitating gene expression, the GAGA factor appears to have a more global role in chromosome structure and function. This is suggested by the spectrum of nuclear cleavage cycle defects observed in Trl13C embryos. These defects include asynchrony in the cleavage cycles, failure in chromosome condensation, abnormal chromosome segregation and chromosome fragmentation. These defects are likely to be related to the association of the GAGA protein with heterochromatic satellite sequences which is observed throughout the cell cycle.

A common translational control mechanism functions in axial patterning and neuroendocrine signaling inDrosophila

Development ◽  
2002 ◽  
Vol 129 (14) ◽  
pp. 3325-3334 ◽  
Author(s):  
Ira E. Clark ◽  
Krista C. Dobi ◽  
Heather K. Duchow ◽  
Anna N. Vlasak ◽  
Elizabeth R. Gavis
Keyword(s):  
Gene Expression ◽  
Translational Control ◽  
Ectopic Expression ◽  
Drosophila Embryo ◽  
Control Element ◽  
Molting Cycle ◽  
Axial Patterning ◽  
Cis Acting ◽  
Maternal Mrnas ◽  
Anterior Posterior

Translational repression of maternal nanos (nos) mRNA by a cis-acting Translational Control Element (TCE) in the nos 3′UTR is critical for anterior-posterior patterning of the Drosophila embryo. We show, through ectopic expression experiments, that the nos TCE is capable of repressing gene expression at later stages of development in neuronal cells that regulate the molting cycle. Our results predict additional targets of TCE-mediated repression within the nervous system. They also suggest that mechanisms that regulate maternal mRNAs, like TCE-mediated repression, may function more widely during development to spatially or temporally control gene expression.

scholarly journals Embryonic geometry underlies phenotypic variation in decanalized conditions

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Anqi Huang ◽  
Jean-François Rupprecht ◽  
Timothy E Saunders
Keyword(s):  
Gene Expression ◽  
Aspect Ratio ◽  
Phenotypic Variation ◽  
Drosophila Embryo ◽  
Wild Type ◽  
Gap Gene ◽  
Key Factor ◽  
Segmentation Gene Expression ◽  
Environmental Variations ◽  
Anterior Posterior

During development, many mutations cause increased variation in phenotypic outcomes, a phenomenon termed decanalization. Phenotypic discordance is often observed in the absence of genetic and environmental variations, but the mechanisms underlying such inter-individual phenotypic discordance remain elusive. Here, using the anterior-posterior (AP) patterning of the Drosophila embryo, we identified embryonic geometry as a key factor predetermining patterning outcomes under decanalizing mutations. With the wild-type AP patterning network, we found that AP patterning is robust to variations in embryonic geometry; segmentation gene expression remains reproducible even when the embryo aspect ratio is artificially reduced by more than twofold. In contrast, embryonic geometry is highly predictive of individual patterning defects under decanalized conditions of either increased bicoid (bcd) dosage or bcd knockout. We showed that the phenotypic discordance can be traced back to variations in the gap gene expression, which is rendered sensitive to the geometry of the embryo under mutations.

scholarly journals Dual mode of embryonic development is highlighted by expression and function of Nasonia pair-rule genes

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Miriam I Rosenberg ◽  
Ava E Brent ◽  
François Payre ◽  
Claude Desplan
Keyword(s):  
Gene Expression ◽  
Embryonic Development ◽  
Mixed Mode ◽  
Complete Loss ◽  
Dual Mode ◽  
Gap Gene ◽  
And Function ◽  
Pair Rule ◽  
Anterior Posterior

Embryonic anterior–posterior patterning is well understood in Drosophila, which uses ‘long germ’ embryogenesis, in which all segments are patterned before cellularization. In contrast, most insects use ‘short germ’ embryogenesis, wherein only head and thorax are patterned in a syncytial environment while the remainder of the embryo is generated after cellularization. We use the wasp Nasonia (Nv) to address how the transition from short to long germ embryogenesis occurred. Maternal and gap gene expression in Nasonia suggest long germ embryogenesis. However, the Nasonia pair-rule genes even-skipped, odd-skipped, runt and hairy are all expressed as early blastoderm pair-rule stripes and late-forming posterior stripes. Knockdown of Nv eve, odd or h causes loss of alternate segments at the anterior and complete loss of abdominal segments. We propose that Nasonia uses a mixed mode of segmentation wherein pair-rule genes pattern the embryo in a manner resembling Drosophila at the anterior and ancestral Tribolium at the posterior.

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