Bicoid (gene)

Bicoid is a maternal effect gene whose protein concentration gradient patterns the anterior-posterior axis during Drosophila embryogenesis. Bicoid was also the first protein demonstrated to act as a morphogen.

Role of Bicoid in axial patterning

bicoid mRNA is actively localized to the anterior of the fruit fly egg during oogenesis along microtubules and retained there through association with cortical actin. Translation of bicoid is regulated by its 3' UTR and begins after egg deposition: diffusion and convection within the syncytium produce an exponential gradient of Bicoid protein within roughly one hour, after which Bicoid nuclear concentrations remain approximately constant through cellularization. An alternative model proposes the formation of a biocid mRNA gradient in the embryo along cortical microtubules which then serves as template for translation of the Bicoid protein to form the Bicoid protein gradient. Bicoid protein represses the translation of caudal mRNA and enhanced the transcription of anterior gap genes including hunchback, orthodenticle, and buttonhead.