Effects of non-lethal Cry1F toxin exposure on the growth, immune response, and intestinal microbiota of silkworm (Bombyx mori)

Abstract

Bt (Bacillus thuringiensis) maize is expected to be commercial cultivated widely in China. When Bt maize is planted near mulberry trees, it renders silkworms (Bombyx mori) vulnerable, as they belong to the same class as the Lepidoptera insects targeted by Bt maize. Cry1F has been found to be highly toxic to silkworms, particularly in their early larval stages. In this study, we aimed to assess the effects of non-lethal Cry1F exposure on the growth, immune response, and intestinal microbiota in silkworms. The results showed that feeding silkworms with mulberry leaves soaked in 100 μg/mL Cry1F for 96 h had an impact on larval body weight acquisition, leading to a decrease in cocoon and pupae weight. Cry1F exposure disrupted the intestinal integrity of silkworms by affecting the columnar cells of the midgut. The activity of detoxification enzymes (CarE, AChE, and GST) as well as antioxidant enzymes (SOD, CAT, and POD) were also affected by Cry1F. After 96 h Cry1F exposure, the evenness of the bacterial community was disrupted, resulting in alterations in the structure of the intestinal microbiota. Additionally, Cry1F exposure affected the relative expression levels of the peritrophic membrane (PM) protein and the corresponding immune pathways genes of silkworms. Most of the immune-related gene expressions were inhibited after exposure to Cry1F toxin but increased with prolonged treatment. This study demonstrates that non-lethal Cry1F exposure can affect the growth, immune response, and intestinal microbiota of silkworm.