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An experiment was executed at field condition to evaluate ecological impact of Bt cotton (Mech 162 + Bt) on soil microbes and Bt protein behavior in soil. Root exudates of Bt cotton plant containing Bt protein enter into soil which persisted in soil for atleast 235 days after sowing (DAS). During vegetative and flowering stage, Bt protein was not detectable in both qualitative and quantitative assay but, during onset of boll formation at 150 DAS, a level of 0.0013 μg/g of Cry 1Ac protein was quantified in rhizospheric soil which further increased exponentially up to 0.0033 μg/g at 195 DAS and then maintained at the same level till 235 DAS with Cry1Ac expression level of 0.0029 μg/g soil. Rhizospheric soil of Bt cotton had significantly higher (p < 0.05) abundance of Fatty Acid Methyl Esters (FAME) of gram positive bacteria. Abundance of polyunsaturated FAMEs that are indicators of fungi, were slightly higher in Bt as compared to non-Bt cotton soils. The metabolic profiling, also called community level physiological profiling (CLPP) showed more microbial functional diversity (Shannon–Wiener Diversity) in soil samples of different growth stages of Bt cotton than its corresponding non-Bt variety. Our results showed that Cry 1AC Bt protein persists in clay loamy soil even after harvesting and significantly altered microbial community composition and functional diversity in rhizospheric soil of Bt cotton than non-Bt. Any possible and unintentional changes in composition of root exudes of Bt cotton could regulate the selection of different microbial communities and thus can alter functional responses. [ABSTRACT FROM AUTHOR]

Transgenic rice with Bacillus thuringiensis (Bt) genes has been successfully cultivated in recent years. The stable and sustainable expression of Bt protein is the guarantee of effective resistance within these strains against target pests. It is well known that the synthesis of Bt protein in Bt crops needs nitrogen (N). Therefore, how is the efficacy of transgenic Bt rice against target pests in response to N application? In our study, we found that enhanced nitrogen inputs increased soluble protein content (SPC) and glutamine synthetase (GS), but decreased amino acid content (AAC); it is evident that the protein synthesis was enhanced, and degradation was reduced with increasing nitrogen application. Thus, both increased protein synthesis and decreased protein degradation contributed to the increased Bt protein content (BTC) in transgenic Bt rice. Responses of the three Bt rice lines to N proportions and N sources were different. All these differences can be explained by the changes of nitrogen metabolism of different genotypes. The BTC in leaves was higher than that in other organs, and the fully expanded green leaf had higher BTC than the senescent leaf and tender leaf. Despite the difference of Bt protein expression, all transgenic rice lines showed 100% resistance to target pests under different N conditions. Our results indicated that the response of Bt protein expression in transgenic Bt rice with different genotypes to N fertilizer was inconsistent; moreover, there exist obvious spatial-temporal differences. Therefore, in order to guarantee the stability and sustainability resistance of Bt rice, it is necessary to adopt appropriate N management practice according to the expression pattern of Bt protein of transgenic Bt rice with different genotypes. [ABSTRACT FROM AUTHOR]

Transgenic Bacillus thuringiensis ( Bt) rice have been reported to acquire effective resistance against the target pests; however, the insertion and expression of alien Bt genes may have some unintended effects on the growth characteristics of rice. A screen-house experiment was conducted and repeated twice to investigate the growth characteristics and Bt protein expressions in two Bt rice lines [MH63 ( Cry2A*) and MH63 ( Cry1Ab/Ac)], which had different Bt protein expression levels in leaves, under zero nitrogen (N0) and recommended nitrogen (NR) fertilizer applications. Compared to the counterpart MH63, MH63 ( Cry2A*) under N0 experienced accelerated leaf senescence and a lower internal N use efficiency (IE), resulting in a 23.2% decrease in grain yield and a lower accumulated biomass. These variations were revealed to be correlated to the higher ratio of the Bt protein content to the soluble protein content (BTC/SPC) with a maximum value of 4.3‰ in MH63 ( Cry2A*) leaves in the late growth stage. Under NR, no differences in growth characteristics between MH63 ( Cry2A*) and MH63 were found. The growth characteristics of MH63 ( Cry1Ab/Ac), with a lower BTC/SPC in the late growth stage compared to MH63 ( Cry2A*), were identical to those of MH63 under the two N applications. Results show that the transgenic Bt rice MH63 ( Cry2A*), with a relatively higher Bt protein expression in the late growth stage, had an inferior adaptation to nitrogen deficiency compared to its non- Bt counterpart. And this inferior adaptation was found to be correlated with the higher BTC/SPC in MH63 ( Cry2A*) leaves in the late growth stage. [ABSTRACT FROM AUTHOR]

As genetic engineering in plants is increasingly used to control agricultural pests, it is important to determine whether such transgenic plants adversely affect non-target organisms within and around cultivated fields. The cry1Ab/1Ac fusion gene from Bacillus thuringiensis ( Bt) has insecticidal activity and has been introduced into rice line Minghui 63 (MH63). We evaluated the effect of transgenic cry1Ab/1Ac rice (Huahui 1, HH1) on paddy frogs by comparing HH1 and MH63 rice paddies with and without pesticide treatment. The density of tadpoles in rice fields was surveyed at regular intervals, and Cry1Ab/1Ac protein levels were determined in tissues of tadpoles and froglets collected from the paddy fields. In addition, Rana nigromaculata froglets were raised in purse nets placed within these experimental plots. The survival, body weight, feeding habits, and histological characteristics of the digestive tract of these froglets were analyzed. We found that the tadpole density was significantly decreased immediately after pesticide application, and the weight of R. nigromaculata froglets of pesticide groups was significantly reduced compared with no pesticide treatment, but we found no differences between Bt and non- Bt rice groups. Moreover, no Cry1Ab/1Ac protein was detected in tissue samples collected from 192 tadpoles and froglets representing all four experimental groups. In addition, R. nigromaculata froglets raised in purse seines fed primarily on stem borer and non-target insects, and showed no obvious abnormality in the microstructure of their digestive tracts. Based on these results, we conclude that cultivation of transgenic cry1Ab/1Ac rice does not adversely affect paddy frogs. [ABSTRACT FROM AUTHOR]

The aquatic Environmental Risk Assessment (ERA) for pesticides relies on standardized experimental protocols focusing on exposure via the water phase or the sediment. Systemic pesticides (e.g., neonicotinoids) or pesticides produced in transgenic plants (e.g., Bt proteins) can be introduced into aquatic ecosystems as part of plant residues. Consequently, they may be taken up by organisms as part of their diet. Here, we analyzed (i) whether standardized aquatic ecotoxicological test guidelines consider an exposure route via food and (ii) whether these tests can be easily modified to take this exposure route into account. From the 156 existing test guidelines, only those for fish and amphibians partly consider a potential route of uptake via food. From the remaining invertebrate guidelines, those focussing on chronic endpoints may be most suitable to cover this exposure path. We suggest assessing the food-related effects of systemic pesticides in a dose-dependent manner using standardized guidelines or methods developed from peer-reviewed literature. For transgenic plants, spiking uncontaminated leaf material with increasing concentrations of the test substances would allow to test for dose responses. After adaption to oral uptake, standard test guidelines currently available for the ERA appear, in principle, suitable for testing effects of systemic pesticides and transgenic plants. [ABSTRACT FROM AUTHOR]