The biolistic method as a tool for testing the differential activity of putative silkmoth chorion gene promoters

Bombyx mori unpaired early chorion gene copies 6F6.1,.2 and .3 are exceptio ns to the typical organization and distribution pattern of known early ErA/ ErB, middle A/B and late HcA/HcB divergently transcribed gene pairs. Contra ry to such pairs, the boundaries of the 6F6 regulatory sequences are not ea sily defined; moreover, they share common sequence elements with the regula tory sequences of middle and late genes. In order to perform a functional s tudy of the tissue and temporal specificity of the 6F6 putative promoter re gion, we decided to apply biolistics. In the present work, use of a region from the 6F6.2 5' untranslated sequence, spanning nucleotides -138 to the c ap site, gave an expected expression pattern of a lacZ reporter gene. Tempo ral specificity was further verified by control experiments using the clone d intergenic sequence of the late gene pair HcA/B.12, which resulted in lac Z expression in late choriogenic follicles. At present, despite the recent successful germinal transgenesis of Bombyx mori, the biolistic transient ex pression system seems to be the most rapid technique to pursue the function al study of the promoter region of early chorion genes, including the three unconventional early 6F6 genes. (C) 2001 Elsevier Science Ltd. All rights reserved.