Figure S1. Specific detection of the anti-30Kc19 antibody in Bombyx. (A) Multiple sequence alignment of 30Kc6 [National Center for Biotechnology Information (NCBI) accession number: NM_001044021.1], 30Kc12 (NCBI accession number: NM_001101726.1), 30Kc19 (NCBI accession number: NM_001101727.1), 30Kc21 (NCBI accession number: NM_001101729.1) and 30Kc23 (NCBI accession number: NM_001101728.2) proteins. The position of the designed polypeptide is labelled with a red line. (B) Amino acid sequence of synthesized polypeptide for the preparation of the anti-30Kc19 antibody. (C) Detection of specificity of polyclonal anti-30Kc19 protein antibody by Western blotting. M, protein molecular weight marker. Red arrow indicates the position of the 30Kc19 protein.


Figure S2. Corresponding negative controls of Fig. 5. Cross-sections of silk glands dissected from (A) silkworms on day 7 of the fifth instar (5L7); (B) at the prepual stage (PP); (C) on day 1 of the pupal stage (P1). Column 1, merged images for FITC and DAPI; column 2, genomic DNA labelled with DAPI; column 3, cross-sections stained with normal rabbit serum and FITC. Diagrams on lines 2, 4 and 6 are amplified sections (red frames) of lines 1, 3 and 5. ‘a’ indicates outside the silk glands, and ‘b’ indicates inside the silk glands. Scale bars = 100 μm.


Figure S3. Detection of DNA ladder in Bombyx silk glands during the larval−pupal stage. M, DNA molecular weight marker, bp; 5L7, day 7 of the fifth instar; W, the wandering stage; S1, day 1 of the spinning stage; S2, day 2 of the spinning stage; PP, the prepupal stage; P1, day 1 of the pupal stage.


Figure S4. Multiple sequence alignment of Bombyx Bm-caspase-1 with Drosophila DRICE and DCP-1. The tripeptide ETD, indicated by the red arrowheads, of DCP-1 [National Center for Biotechnology Information (NCBI) accession number: NM_057626.3] and DRICE (NCBI accession number: NM_057626.3) is the apoptotic epitope exposed by DRONC activity. It was found that the tripeptide ETD may also be the apoptotic epitope of Bm-caspase-1 (NCBI accession number: NM_001043585.1), so the human cleaved-caspase-3 antibody could be used to detect DRONC activity in Bombyx.

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