Impact of Water Content and Temperature on the Degradation of Cry1Ac Protein in Leaves and Buds of Bt Cotton in the Soil

Abstract

Determining the influence of soil environmental factors on degradation of Cry1Ac protein from Bt cotton residues is vital for assessing the ecological risks of this commercialized transgenic crop. In this study, the degradation of Cry1Ac protein in leaves and in buds of Bt cotton in soil was evaluated under different soil water content and temperature settings in the laboratory. An exponential model and a shift-log model were used to fit the degradation dynamics of Cry1Ac protein and estimate the DT50 and DT90 values. The results showed that Cry1Ac protein in the leaves and buds underwent rapid degradation in the early stage (before day 48), followed by a slow decline in the later stage under different soil water content and temperature. Cry1Ac protein degraded the most rapidly in the early stage at 35°C with 70% soil water holding capacity. The DT50 values were 12.29 d and 10.17 d and the DT90 values were 41.06 d and 33.96 d in the leaves and buds, respectively. Our findings indicated that the soil temperature was a major factor influencing the degradation of Cry1Ac protein from Bt cotton residues. Additionally, the relative higher temperature (25°C and 35°C) was found to be more conducive to degradation of Cry1Ac protein in the soil and the greater water content (100%WHC) retarded the process. These findings suggested that under appropriate soil temperature and water content, Cry1Ac protein from Bt cotton residues will not persist and accumulate in soil.

Effects of water management practices on residue decomposition and degradation of Cry1Ac protein from crop-wild Bt rice hybrids and parental lines during winter fallow season

“…A.1A) compared with the range of 0.5-11.4°C, 0.2-11.3°C and 7.7-15.4°C at the three sites in our previous study (Xiao et al, 2014), which may have led to the increased level of k c . These results confirm the effects of temperature and water content on the degradation of the Cry1Ab protein released from the Bt crop residue in field soil, similar to the laboratory results presented by Feng et al (2011) and Zhang et al (2015).We found that k c derived from both conditions was positively correlated with the initial concentration of the Cry1Ac protein in rice residues. This finding was supported by Wang et al (2007) who revealed that k c decreased as the concentration of purified Cry1Ab protein in aqueous solutions declined.…”

“…In the current study, the decay of the Cry1Ac protein was well described using a first-order kinetics model, which is consistent with previous studies (e.g., Wang et al, 2006b;Xiao et al, 2014;Zhang et al, 2015). Furthermore, the degradation of the Bt protein in rice residue did vary with water management practices in the field as hypothesized.…”

“…Unlike the pattern in which k m varied between the two water conditions, the k c values for 6, 2 and 1 out of 9 litter types under the aerobic condition were significantly greater, equivalent and significantly lower, respectively, in comparison with those under the flooded condition (Table 3). Here, we confirmed a faster degradation of the Bt protein under aerobic conditions than under flooded conditions in the field, similar to two laboratory studies (Wang et al, 2007;Zhang et al, 2015), which may be attributed to varied microbial mediated degradation of the Bt protein (Crecchio and Stotzky, 2001). In addition, greater values of k c were derived from the aerobic field in comparison with those reported in our previous investigations that were also carried out under aerobic field conditions (Xiao et al, 2014).…”

“…The DT50 (50% degradation time) of the Cry2A protein in Bt cotton was 15.5 and 31.7 days under laboratory and field degradation, respectively (Sims and Ream, 1997). In contrast, Zhang et al (2015) reported that the DT50 of the Cry1Ac protein in the leaves and buds of Bt cotton in the soil was 12.29 and 10.17 days, respectively, in the laboratory. Literature on the degradation of the Bt protein in rice residues in the field is scarce.…”

Comparison of Catalytic and Immunological Amylase Tests for Identifying of Saliva from Degraded Samples

“…Moreover, there were no significant differences in the detectability of both tests when saliva samples were incubated in dried-soil (37°C, 0-72 h). These results suggest that environmental microbial effects (e.g., protein degradation) require environmental humidity (18,23).…”