Enhancement of antiviral capacity of transgenic silkworms against cytoplasmic polyhedrosis virus via knockdown of multiple viral genes.

Bombyx mori cytoplasmic polyhedrosis virus (BmCPV), a major pathogen of silkworms, causes serious economic losses in sericulture. The BmCPV genome contains 10 discrete dsRNA segments; among these, S1, S2, S3, S4, S6, and S7 encode virus structural proteins, whereas S5, S8, S9, and S10 encode nonstructural proteins. In an attempt to create an anti-BmCPV silkworm strain, we constructed transgenic RNAi vector pb-CNS for knockdown of S5, S8, S9, and S10, and pb-SNS targeting S1, S2, S4, S5, and S8.

Transcriptome analysis of interactions between silkworm and cytoplasmic polyhedrosis virus.

Bombyx mori cytoplasmic polyhedrosis virus (BmCPV) specifically infects silkworm midgut (MG) and multiplication occurs mainly in posterior midgut (PM). In this study, MG and fat body (FB) were extracted at 0, 3, 24, and 72 h after BmCPV infection. The total sequence reads of each sample were more than 1510000, and the mapping ratio exceeded 95.

The 5'-UTR intron of the midgut-specific BmAPN4 gene affects the level and location of expression in transgenic silkworms.

Introns are important for regulating gene expression. BmAPN4, which has a 5'-UTR upstream intron (5 UI), is specifically expressed in the entire silkworm midgut. In our previous study, the promoter region upstream of the 5 UI of BmAPN4 was cloned and identified as the P3 promoter (P3P) with activity only in the anterior midgut.

Overexpression of host plant urease in transgenic silkworms.

Bombyx mori and mulberry constitute a model of insect-host plant interactions. Urease hydrolyzes urea to ammonia and is important for the nitrogen metabolism of silkworms because ammonia is assimilated into silk protein. Silkworms do not synthesize urease and acquire it from mulberry leaves.

Postintegration stability of the silkworm piggyBac transposon.

The piggyBac transposon is the most widely used vector for generating transgenic silkworms. The silkworm genome contains multiple piggyBac-like sequences that might influence the genetic stability of transgenic lines. To investigate the postintegration stability of piggyBac in silkworms, we used random insertion of the piggyBac [3 × p3 EGFP afm] vector to generate a W chromosome-linked transgenic silkworm, named W-T.

Identification of a midgut-specific promoter in the silkworm Bombyx mori.

The midgut is an important organ for digestion and absorption of nutrients and immune defense in the silkworm Bombyx mori. In an attempt to create a tool for midgut research, we cloned the 1080 bp P2 promoter sequence (P2P) of a highly expressed midgut-specific gene in the silkworm. The transgenic line (P2) was generated via embryo microinjection, in which the expression of EGFP was driven by P2P.

A transgenic animal with antiviral properties that might inhibit multiple stages of infection.

Bombyx mori nucleopolyhedrovirus (BmNPV) is the primary pathogen of silkworms, causing severe economic losses in sericulture. To create antiviral silkworm strains, we constructed a transgenic vector in which the dsRNA for five tandem BmNPV genes was controlled by the BmNPV hr3 enhancer and IE1 promoter. The antivirus gene Bmlipase-1 was driven by B.