Patterns of region-specific chorion gene expression in the silkmoth and identification of shared 5' flanking genomic elements.

Time-dependent and cell-specific changes in concentrations of total RNA, of poly A+ RNA, and of specific mRNAs have been measured throughout silkmoth choriogenesis. Levels of total RNA and of poly A+ RNA are maintained throughout much of choriogenesis, but decrease at least fourfold during the very late period, in parallel with a decrease in overall protein synthesis. Very late period changes in total RNA and in poly A+ RNA are less pronounced in the aeropyle crown region, where a subset of chorion proteins is preferentially synthesized, than in the flat region.

Molecular cloning of region-specific chorion-encoding RNA sequences.

We have constructed a cDNA clone library from poly(A)+ RNA of very-late-period choriogenic silkmoth follicles. Clone DNAs that hybridize preferentially to RNA from the aeropyle crown region of the follicle (versus the flat region) were selected, and all could be placed in one of two homology groups. The two groups represent sequences encoding the very-late-period chorion proteins E1 and E2; this was established by hybrid-selected translation coupled with specific antibody precipitation.