|
|
|
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
|
Fig. 2. Patterning the dorsal side of the Drosophila embryo by BMP
transport. (A) Dpp is transcribed uniformly within the dorsal half
of the embryo in the early blastoderm. (B) Initially, Mad
phosphorylation is wide and of low intensity at the mid-cellular stage, but
then refines during late blastoderm into a sharper and more intense stripe.
The refinement requires an additional unknown factor that is induced by the
early low-level Dpp signal (see Wang and
Ferguson, 2005). (C) A schematic cross-sectional
representation of an embryo showing the expression domains of the various
extracellular components (red, sog; blue, tsg and
tld; green, area of overlap in dpp and scw
expression). Sog diffuses into the dorsal domain from its ventrolateral site
of synthesis, and preferentially complexes with Dpp/Scw heterodimers and Tsg.
(D) Net diffusion of this complex, driven in part by Tld processing of
Sog, promotes accumulation of the Dpp/Scw heterodimer near the midline from
mid- to late-cellular blastoderm stage. Homodimers of Dpp and Scw are not
transported efficiently as they have a lower affinity for the Sog/Tsg complex
(see Shimmi et al., 2005b).
(E) The spatial distribution of BMP-bound receptor at various times
obtained using modeling methods similar to those described by Mizutani et al.
(Mizutani et al., 2005) in
which there is a constant BMP production/degradation. Note that the model
predicts that, at a given threshold, the intensity of the pMad stripe should
both increase in time and widen. NE, neuroectoderm; DM, dorsal midline.
|
