Dynamics of Cry1Ac protein and soil enzyme activity in the rhizosphere of transgenic Bt oilseed rape

In this study, three insect-resistant transgenic Bacillus thuringiensis (Bt) Bt ) oilseed rape events (GT1, GT5 and GT9) under field conditions were utilised to analyse the dynamics of Cry1Ac protein and the changes in soil enzyme activities in the rhizosphere soil of transgenic Bt plants during different growth stages over two successive cultivation years. The results indicated that compared to the non-transgenic control plant cv. Westar, the amount of Cry1Ac protein in the rhizosphere soil of the three transgenic oilseed rape events was significantly higher during the flowering and podding stages in the first cultivation year. Additionally, in the second cultivation year, transgenic GT1 and GT9 had significantly higher amounts of Cry1Ac protein in the rhizosphere soil during the flowering stage, and all three transgenic oilseed rape events had significantly higher amounts of Cry1Ac protein in the rhizosphere soil during the podding stage. Over the two successive cultivation years, the sucrase activity in the rhizosphere soil of transgenic events showed significant changes during bolting, flowering and podding stages, while all three transgenic events exhibited significant changes in phosphatase activity during the four different stages. Furthermore, different transgenic events showed varying significant changes in urease and protease activities during the bolting, flowering and podding stages of the first year, and all three transgenic events had significant changes in dehydrogenase activities during the four different stages of the second cultivation year. PCA and correlation analysis clearly demonstrated a strong correlation between the Cry1Ac protein and five soil enzyme activities, as well as a close interconnectedness among those five soil enzyme activities. These findings suggest that the amount of insecticidal crystal proteins in the rhizosphere soil of transgenic Bt (Cry1Ac) oilseed rape varies with different growth periods, and the enzyme activities in the rhizosphere soil of transgenic Bt oilseed rape plants undergo significant changes over two successive planting years.