D. Morisato et Kv. Anderson, SIGNALING PATHWAYS THAT ESTABLISH THE DORSAL-VENTRAL PATTERN OF THE DROSOPHILA EMBRYO, Annual review of genetics, 29, 1995, pp. 371-399
The dorsal-ventral pattern of the Drosophila embryo is established by
three sequential signaling pathways. Each pathway transmits spatial in
formation by localizing the activity of an extracellular signal, which
acts as a ligand for a broadly distributed transmembrane receptor. Th
e components of the first two pathways are encoded by maternal effect
genes, while the third pathway is specified by genes expressed in the
zygote. During oogenesis, the oocyte transmits a signal to the surroun
ding follicle cells by the gurken-torpedo pathway. After fertilization
, the initial asymmetry of the egg chamber is used by the spatzle-Toll
pathway to generate within the embryo a nuclear gradient of the trans
cription factor Dorsal, which regulates the regional expression of a s
et of zygotic genes. On the dorsal side of the embryo, the decapentapl
egic-punt/thick veins pathway then establishes patterning of the amnio
serosa and dorsal ectoderm. Each pathway uses a distinct strategy to a
chieve spatial localization of signaling activity.