SPATIAL AND TEMPORAL EXPRESSION PATTERN OF POU-M1 SGF-3 IN BOMBYX-MORI EMBRYOGENESIS/

The expression pattern of the POU-M1/SGF-3 gene during Bombyx embryoge nesis has been analysed using in situ hybridization and immunohistoche mistry. At the early embryo retraction stage, both the transcripts and protein were first detected in precursor cells of the prothoracic gla nds in the labial segment in the oenocytes in the A1-A8 segments and i n invaginated regions in the mandibular and maxillary segments. The in vaginated regions in the mandibular segment develop into the abductor plates in the lateral anterior region and the adductor plates in the p osterior region. From the latter plates, the salivary glands elongate. The invaginated regions in the maxillary segment develop into the cor pora allata in the anterior region and the subbuccal glands in the pos terior region, which unite with tissues of the anterior region of the mandibular segment at later stages. After the embryo retraction stage, the transcripts and protein products also become detectable in the si lk gland invagination points and, after the blastokinesis stage, the p roducts are restricted to the entire anterior silk glands and to the a nterior and middle parts of the middle silk glands. Expression can als o be detected in a part of the hindgut, in the tracheal system and in some cells of the central nervous system. These results indicate that POU-M1/SCF-3 might play roles in the development of the silk glands, n ervous system, tracheal system and other organs like the prothoracic g lands and oenocytes.