Spatial and temporal expression pattern of Bombyx fork head SGF-1 gene in embryogenesis

The embryonic expression of Bombyx fkh/SGF-1 gene has been analysed using in situ hybridization and immunohistochemistry. Both transcripts and protein were first detected in the most anterior and posterior regions at the time of germ anlage formation, and were successively expressed in the foregut and hindgut at later stages. A weaker expression was also detected in the elongated midgut. By the time embryo retraction was finished transcripts and protein were also detectable in the invaginated whole silk glands, and after the blastokinesis stage the products were restricted to the middle and posterior sill; glands achieving a state required for the SGF-I distribution for later stages. Expression could also be detected in the central and peripheral nervous systems. From these observations, we propose that Bombyx Fkh/SGF-1 may play a pole in organogenesis processes such as those of the gut, silk glands, and nervous systems, act as a region specific homeotic gene, and in spite of clear embryonic developmental differences between Drosophila and Bombyx, two terminals may be determined by region specific genes such as Bombyx fkh/SGF-1 as opposed to segmental development.