Abstract
Although naturally colored silk is an excellent textile material and biomedical material, some silkworm varieties—such as the bivoltine strain Jinqiu × Churi—exhibit a relatively low cocoon shell ratio, which limits their economic value. This study, therefore, aimed to develop a novel approach to enhance larval survival and cocoon quality by orally administering a single dose of a recombinant pIEx-1-FKBP12B plasmid to silkworm larvae at different instars. The optimal feeding larval stages and dosage were evaluated based on the enhancement of alkaline phosphatase activity, mortality rate, cocoon shell weight, cocoon shell ratio, and silk weight. The best results were observed in the group that received a single oral dose of 5 μg of recombinant pIEx-1-FKBP12B plasmid during the second instar. This group exhibited significantly higher alkaline phosphatase activity and fifth instar larval body length compared to the group receiving wild plasmid pIEx-1. The cocoon shell weight was 21.96% higher, the cocoon shell ratio was 2.5% higher, and the silk weight was 33.60% higher than that of the control group. The mortality rate was the lowest among all the groups, 36.89% lower than the control group. These findings suggest that oral administration of the pIEx-1-FKBP12B plasmid has significant potential for application in improving silk quality.