Response of the Propylea japonica Microbiota to Treatment with Cry1B Protein.

Propylea japonica (Thunberg) (Coleoptera: Coccinellidae) is a dominant natural enemy of insect pests in farmland ecosystems. It also serves as an important non-target insect for environmental safety evaluations of transgenic crops. Widespread planting of transgenic crops may result in direct or indirect exposure of P. japonica to recombinant Bacillus thuringiensis (Bt) protein, which may in turn affect the biological performance of this natural enemy by affecting the P. japonica microflora. However, the effects of Bt proteins (such as Cry1B) on the P. japonica microbiota are currently unclear. Here, we used a high-throughput sequencing method to investigate differences in the P. japonica microbiota resulting from treatment with Cry1B compared to a sucrose control. The results demonstrated that the P. japonica microbiome was dominated by Firmicutes at the phylum level and by Staphylococcus at the genus level. Within-sample (α) diversity indices demonstrated a high degree of consistency between the microbial communities of P. japonica treated with the sucrose control and those treated with 0.25 or 0.5 mg/mL Cry1B. Furthermore, there were no significant differences in the abundance of any taxa after treatment with 0.25 mg/mL Cry1B for 24 or 48 h, and treatment with 0.5 mg/mL Cry1B for 24 or 48 h led to changes only in Staphylococcus, a member of the phylum Firmicutes. Treatment with a high Cry1B concentration (1.0 mg/mL) for 24 or 48 h caused significant changes in the abundance of specific taxa (e.g., Gemmatimonades, Patescibacteria, Thauera, and Microbacterium). However, compared with the control, most taxa remained unchanged. The statistically significant differences may have been due to the stimulatory effects of treatment with a high concentration of Cry1B. Overall, the results showed that Cry1B protein could alter endophytic bacterial community abundance, but not composition, in P. japonica. The effects of Bt proteins on endophytes and other parameters in non-target insects require further study. This study provides data support for the safety evaluation of transgenic plants.

Transgenic cotton expressing Cry1B protein has no adverse effect on predatory insect Propylea Japonica.

The lady beetle Propylea japonica is a dominant natural predator of insect pests in farmland ecosystems and an important non-target indicator insect for the environmental safety assessment of GM crops. The commercial cultivation of GM crops may cause P. japonica to frequently be exposed to the Bt protein environment. In this study, the biological characteristics, enzyme activity, and expression levels of detoxification and metabolism in P. japonica were studied after Cry1B protein treatment. No significant differences were observed in developmental duration, emergence rate, or body weight at different ages after feeding larvae 0.5 mg/mL of Cry1B protein compared with the control. Furthermore, there were no significant differences in the activities of glutathione S-transferase (GST), catalase (CAT), and peroxidase (POD) after feeding 0.25 mg/mL and 0.5 mg/mL Cry1B protein. However, when the concentration of Cry1B protein increased to 1.0 mg/mL, the activities of the GST, CAT, and POD increased significantly. Compared with the control group, there were no significant differences in the expression levels of most detoxification metabolism related genes; only a few genes had changed expression levels at the individual concentrations (CYP345B1, CYP4Q2, CYP9F2, GST, and microsomal GST). Overall, these results suggest that Cry1B protein has little or no effect on the biological characteristics of P. japonica. Genes related to enzyme activity and detoxification are differentially expressed at high concentration stimulation. Therefore, this research suggests that the potential risks of Cry1B for the predator P. japonica are negligible.