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. 2007 May 11;104(21):8941–8946. doi: 10.1073/pnas.0702860104

Fig. 1.

Fig. 1.

Difference in the CBP gene structure between Y and +Y allele strains. (A) Schematic structure of the CBP cDNA sequence. CBP consists of exons 1–7. Arrows indicate the PCR-primers used in D. (B) A schematic structure of the CBP genomic sequence in the Y and +Y allele strains. Note that the copy number differs between strains. CATS (shaded box) is a non-LTR retrotransposon. (C) Detection of CBP mRNA in the larval midgut by Northern blotting. The exon 2 probe is for the portion of exon 2 that is not truncated in the +Y sequence. A 4.4-kb RNA of the BmStart1 gene (14), an alternative splicing isoform of the CBP gene, was detected with the exon 3–5 probe with a longer detection time [see supporting information (SI) Fig. 4]. (D) RT-PCR analysis of the CBP gene. The primers used are indicated in A. (E) Model of the mechanism by which the difference in CBP genomic sequence affects CBP protein expression and resulting hemolymph and cocoon color. In the +Y allele strain, the splicing out of exon 2, likely associated with the CATS insertion and subsequent genomic deletion, generates a nonfunctional mRNA lacking the true start methionine. This results in an inability to produce CBP protein and the formation of colorless hemolymph and white cocoons.