1 research outputs found
A Precise Bicoid Gradient Is Nonessential during Cycles 11β13 for Precise Patterning in the Drosophila Blastoderm
Background: During development, embryos decode maternal morphogen inputs into highly precise zygotic gene
expression. The discovery of the morphogen Bicoid and its profound effect on developmental programming in the
Drosophila embryo has been a cornerstone in understanding the decoding of maternal inputs. Bicoid has been described as
a classical morphogen that forms a concentration gradient along the antero-posterior axis of the embryo by diffusion and
initiates expression of target genes in a concentration-dependent manner in the syncytial blastoderm. Recent work has
emphasized the stability of the Bicoid gradient as a function of egg length and the role of nuclear dynamics in maintaining
the Bicoid gradient. Bicoid and nuclear dynamics were observed but not modulated under the ideal conditions used
previously. Therefore, it has not been tested explicitly whether a temporally stable Bicoid gradient prior to cellularization is
required for precise patterning.
Principal Findings: Here, we modulate both nuclear dynamics and the Bicoid gradient using laminar flows of different
temperature in a microfluidic device to determine if stability of the Bicoid gradient prior to cellularization is essential for
precise patterning. Dramatic motion of both cytoplasm and nuclei was observed prior to cellularization, and the Bicoid
gradient was disrupted by nuclear motion and was highly abnormal as a function of egg length. Despite an abnormal Bicoid
gradient during cycles 11β13, Even-skipped patterning in these embryos remained precise.
Conclusions: These results indicate that the stability of the Bicoid gradient as a function of egg length is nonessential
during syncytial blastoderm stages. Further, presumably no gradient formed by simple diffusion on the scale of egg length
could be responsible for the robust antero-posterior patterning observed, as severe cytoplasmic and nuclear motion would
disrupt such a gradient. Additional mechanisms for how the embryo could sense its dimensions and interpret the Bicoid
gradient are discussed