Low temperature causes accumulation of unspliced fibroin mRNA precursor molecules in silkworm larvae.

Silk fibroin premessenger mRNA is a large (17 kb) molecule containing a single intron. Previous S1 mapping studies yielded evidence of processing cleavages at sites within the intron, in addition to the major cleavages at the intron/exon boundaries. We have performed S1 mapping experiments using RNA from animals which had been incubated at low temperature. These experiments show a marked accumulation of full-length fibroin mRNA precursor relative to controls, and a reduction in the abundance of molecules lacking portions of the intron. These results demonstrate a partial uncoupling of transcription and splicing in vivo.