Safety Assessment of Bacillus thuringiensis Insecticidal Proteins Cry1C and Cry2A with a Zebrafish Embryotoxicity Test

The food safety assessment of all-female common carp (Cyprinus carpio) (cyp17a1+/-;XX genotype) generated using genome editing technology

There are several technical challenges and public issues concerning genome editing applications before they become viable in commercial aquaculture. Recently, we developed a novel strategy to generate all-female (AF) common carp, which exhibited a growth advantage over the control carp, using genetic editing through single gene-targeting manipulation. Here, we found that the body weight of the AF common carp was higher by 22.58% than that of the control common carp. Because the genotype of the AF common carp was cyp17a1+/-;XX, the contents of sex steroids were normally synthesized, as they were comparable to that of the control female carp. To evaluate the food safety of the AF carp, Wistar rats were fed a diet containing control female carp (control, C) or all-female (AF) carp at an incorporation rate of 5, 10 and 20% (w/w) for 90 days. Compared with those fed control carp, the rats fed AF common carp exhibited no significant difference in body weight, food intake, feed conversion ratio, hematology, serum biochemistry, urine test, relative organ weight, gross necropsy, and histopathological examination. This is the first food safety assessment of the farmed fish strain cultured using CRISPR/Cas9, which will further advance the fishery development of genome-edited animals.

A 90-day feeding study of genetically modified maize LP007-1 in wistar han RCC rats

LP007-1 is a variety of insect-resistant and herbicide-tolerant maize containing the modified cry1Ab, cry2Ab, vip3Aa and cp4-epsps genes. The food safety assessment of the maize LP007-1 was conducted in Wistar Han RCC rats by a 90-days feeding study. Maize grains from both LP007-1 or its corresponding non-genetically modified control maize AX808 were incorporated into rodent diets at 25% and 50% concentrations by mass and administered to rats (n = 10/sex/group) for 90 days. A commercialized rodent diet was fed to an additional group as the basal-diet group. The diets of all groups were nutritionally balanced. No biologically relevant differences were observed in rats fed with maize LP007-1 compared to rats fed with AX808 and the basal-diet with respect to body weight/gain, food consumption/utilization, clinical signs, mortality, ophthalmology, clinical pathology (hematology, prothrombin time, activation of partial thrombin time, serum chemistry, urinalysis), organ weights, and gross and microscopic pathology. Considering the circumstances of this study, the results provided evidence that LP007-1 maize did not exhibit toxicity in the 90-day feeding study.

An innovative insecticidal approach based on plant protease inhibitor and Bt protoxins inhibits trypsin-like activity in zebrafish

The Leucaena leucocephala trypsin inhibitor (LTI) + Bacillus thuringiensis (Bt) protoxins mix has been proposed as a novel larvicide agent in order to control the vector mosquito of dengue virus, Aedes aegypti, in their aquatic breeding sites. However, use of this insecticide formulation has raised concerns about its impacts on aquatic biota. In this context, this work aimed to assess the effects of LTI and Bt protoxins, separately or in combination, in zebrafish, in regard to the evaluation of toxicity at early life stages and to the presence of LTI inhibitory effects on intestinal proteases of this fish. Results showed that LTI and Bt concentrations (250 mg/L, and 0.13 mg/L, respectively), and LTI + Bt mix (250 mg/L + 0.13 mg/L) - 10 times superior to those with insecticidal action - did not cause death nor did it induce morphological changes during embryonic and larval development (3 to 144 h post-fertilization) of zebrafish. Molecular docking analyses highlighted a possible interaction between LTI and zebrafish trypsin, especially through hydrophobic interactions. In concentrations near to those with larvicidal action, LTI (0.1 mg/mL) was able to inhibit in vitro intestinal extracts of trypsin in female and male fish by 83 % and 85 %, respectively, while LTI + Bt mix promoted trypsin inhibition of 69 % in female and 65 % in male ones. These data show that the larvicidal mix can potentially promote deleterious effects to nutrition and survival in non-target aquatic organisms, especially those with trypsin-like dependent protein digestion.

Safety assessment of subchronic feeding of insect-resistant and herbicide-resistant transgenic soybeans to juvenile channel catfish (Ictalurus punctatus)

Transgenic soybean is one of the most planted crops for human food and animal feed. The channel catfish (Ictalurus punctatus) is an important aquatic organism cultured worldwide. In this study, the effect of six different soybean diets containing: two transgenic soybeans expressing different types of cp4-epsps, Vip3Aa and pat genes (DBN9004 and DBN8002), their non-transgenic parent JACK, and three conventional soybean varieties (Dongsheng3, Dongsheng7, and Dongsheng9) was investigated in juvenile channel catfish for eight weeks, and a safety assessment was performed. During the experiment, no difference in survival rate was observed in six groups. The hepatosomatic index (HSI) and condition factor (CF) showed no significant difference. Moreover, comparable feed conversion (FC), feeding rate (FR), and feed conversion ratio (FCR) were found between transgenic soybean and JACK groups. Assessment of growth performance showed that the weight gain rate (WGR) and specific growth rate (SGR) of channel catfish were consistent. In addition, there were no changes in enzyme activity indexes (lactate dehydrogenase (LDH), total antioxidant capacity (T-AOC), aspartate aminotransferase (AST) and alanine aminotransferase (ALT)) in channel catfish among treatments. The research provided an experimental basis for the aquaculture feed industry to employ transgenic soybean DBN9004 and DBN8002 for commercial purposes.

The Role of Beneficial Microorganisms in Soil Quality and Plant Health

The practice of agriculture has always been a source of food production. The increase in the global population leads to improvements in agriculture, increasing crop quality and yield. Plant growth results from the interaction between roots and their environment, which is the soil or planting medium that provides structural support as well as water and nutrients to the plant. Therefore, good soil management is necessary to prevent problems that will directly affect plant health. Integrated crop management is a pragmatic approach to crop production, which includes integrated pest management focusing on crop protection. Currently, there is an extended idea that many microorganisms, such as fungi or bacteria, are useful in agriculture since they are attractive eco-friendly alternatives to mineral fertilizers and chemical pesticides. The microbes that interact with the plants supply nutrients to crops, control phytopathogens and stimulate plant growth. These actions have beneficial implications in agriculture. Despite the great benefits of microorganisms in agriculture, their use has been quite limited; however, there has been great growth in recent years. This may be because more progress is needed in field applications. One of the most employed genera in agriculture is Bacillus since it has several mechanisms to act as biofertilizers and biopesticides. In this review, the role of beneficial microorganisms, with special emphasis on the Bacillus genus, in soil and plant health will be discussed, highlighting the recent advances in this topic.

Food safety, food security and genetically modified organisms in Africa: a current perspective

Moving forward from 2020, Africa faces an eminent challenge of food safety and security in the coming years. The World Food Programme (WFP) of the United Nations (UN) estimates that 20% of Africa's population of 1.2 billion people face the highest level of undernourishment in the world, likely to worsen due to COVID-19 pandemic that has brought the entire world to its knees. Factors such as insecurity and conflict, poverty, climate change and population growth have been identified as critical contributors to the food security challenges on the continent. Biotechnological research on Genetically Modified Organisms (GMOs) provides a range of opportunities (such as increased crop yields, resistance to pests and diseases, enhanced nutrient composition and food quality) in addressing the hunger, malnutrition and food security issues on the continent. However, the acceptance and adoption of GMOs on the continent has been remarkably slow, perhaps due to contrasting views about the benefits and safety concerns associated with them. With the reality of food insecurity and the booming population in Africa, there is an eminent need for a more pragmatic position to this debate. The present review presents an overview of the current situation of food safety and security and attempts to reconcile major viewpoints on GMOs research considering the current food safety and security crisis in the African continent.

Assessing the effects of an acute exposure to worst-case concentration of Cry proteins on zebrafish using the embryotoxicity test and proteomics analysis

Cry1C, Cry1F and Cry1Ab are insecticidal proteins from Bacillus thuringiensis (Bt) which are expressed in transgenic crops. Given the entry of these proteins into aquatic environments, it is relevant to evaluate their impacts on aquatic organisms. In this work, we sought to evaluate the effects of Cry1C, Cry1F and Cry1Ab on zebrafish embryos and larvae of a predicted worst-case scenario concentration of these proteins (set to 1.1 mg/L). For that, we coupled a traditional toxicity approach (the zebrafish embryotoxicity test and dosage of enzymatic biomarkers) to gel free proteomics analysis. At the concentration tested, these proteins did not cause adverse effects in the zebrafish early life stages, either by verifying phenotypic endpoints of toxicity or alterations in representative enzymatic biomarkers (catalase, glutathione-S-tranferase and lactate-dehydrogenase). At the molecular level, the Cry proteins tested lead to very small changes in the proteome of zebrafish larvae. In a global way, these proteins upregulated the expression of vitellogenins. Besides that, Cry1C e Cry1F deregulated heterogeneous nuclear ribonucleoproteins (Hnrnpa0l and Hnrnpaba, respectively), implicated in mRNA processing and gene regulation. Overall, these data lead to the conclusion that Cry1C, Cry1F and Cry1Ab proteins, even at a very high concentration, have limited effects in the early stages of zebrafish life.

A 90-day subchronic toxicity study of transgenic cotton expressing Cry1Ac, Cry2A and CP4-EPSPS proteins in Sprague-Dawley rats

Genetically engineered crops expressing insecticidal and herbicide-tolerant traits offer a new strategy for crop protection and enhanced production; however, at the same time present a challenge in terms of toxicology and safety. The current experiment presents the findings of a 90-day feeding study in Sprague-Dawley rats with transgenic cottonseed which is expressing insecticidal Cry proteins (Cry1Ac and Cry2A), and tolerant to the herbicide glyphosate. There were 100 rats in this experiment divided into 5 groups of 10 rats/sex/group. Cottonseed from transgenic and control (near-isogenic) lines was formulated into standard diets at levels of 10% and 30% (w/w). All formulated diets were nutritionally balanced. Overall appearance, feed consumption, body weight, organ weight, haematology, serum chemistry and urinalysis were comparable between control and treatment groups. In addition, there was no treatment-related difference in findings of microscopic histopathology and gross appearance of tissues. In conclusion, following the 13-week of feeding transgenic cottonseed, no treatment-related adverse effects were observed in any of the parameters measured in this experiment. Thus, this study demonstrated that transgenic cottonseeds do not cause toxicity and are nutritionally equivalent to its conventional counterpart.

Bacillus thuringiensis protein Vip3Aa does not harm the predator Propylea japonica: A toxicological, histopathological, biochemical and molecular analysis

The ladybeetle Propylea japonica is a widely distributed natural enemy in many agricultural systems. P. japonica is often used as a test organism for safety assessments of transgenic Bacillus thuringiensis crops. Plant varieties expressing the Vip3Aa insecticidal protein are not currently commercially available in China. In this study, protease inhibitor E-64 was used as a positive control to examine the responses of P. japonica larvae to a high concentration of Vip3Aa proteins. Larvae that were fed E-64 had increased mortality and prolonged developmental period, but these parameters were unaffected when larvae were fed Vip3Aa. The epithelial cells of midguts were intact and closely connected with the basal membrane when larvae were fed Vip3Aa, but the epithelial cells degenerated in the E-64 treatment. The activities of antioxidative enzymes and expression levels of detoxification-related genes in P. japonica larvae were not altered after exposure to Vip3Aa; however, these biochemical and molecular parameters were significantly changed in the E-64 treatment. The results demonstrate that Vip3Aa protein is not harmful to the predator P. japonica.

Cry78Ba1, One Novel Crystal Protein from Bacillus thuringiensis with High Insecticidal Activity against Rice Planthopper

The rice planthopper is a very important hemipteran pest that preys on rice and substantially affects the safety of rice production. Moreover, the long-term prevention and control of these pests with chemical pesticides has led to an increase in the resistance of the rice planthopper as well as serious environmental pollution and food safety problems. Bacillus thuringiensis (Bt) has been used for the efficient and green control of a variety of rice pests. Therefore, based on the high-throughput screening of Bt strains that are active against the rice planthopper, we found that Bt strain B4F11 showed certain insecticidal activity against Laodelphax striatellus Fallén, and we have identified a novel insecticidal protein Cry78Ba1 from the Bt strain B4F11, which is expected to provide the specific and safe control of the rice planthopper. The Cry78Ba1 protein is composed of 380 amino acid residues with a molecular weight of 42.55 kDa and contains conserved Ricin_B_Lectin and Toxin_10 superfamily domains. It displays high insecticidal activity against L. striatellus with a lethal concentration (LC₅₀) of 9.723 μg/mL. More importantly, this Toxin_10-like protein does not display sequence homology to any known allergen and can be degraded and inactivated rapidly when heated at 90 °C and in simulated gastrointestinal fluid. In summary, Cry78Ba1 has great potential for applications in the efficient and safe prevention and control of the rice planthopper.

A multi-generational risk assessment of Cry1F on the non-target soil organism Folsomia candida (Collembola) based on whole transcriptome profiling

The Bacillus thuringiensis toxin Cry1F has been used to develop insect-resistant genetically engineered crops. There has been great interest in evaluating its potential risk to non-target organisms (NTOs). However, the majority of previous risk assessments only examined one generation of NTOs using several physiological indicators, which cannot comprehensively detect some potential sub-lethal effects at the molecular level. In this study, we conducted a laboratory-based, multi-generational risk assessment of Cry1F for the collembolan Folsomia candida, an important representative of soil arthropods in terms of survival, reproduction, and differentially expressed genes (DEGs) identified from whole transcriptome profiles. Our results demonstrated that Cry1F was continuously ingested by collembolans over three consecutive generations, but it did not affect the survival or reproduction of F. candida. There were no significant differences in the global gene expression between F. candida—fed diets with and without Cry1F, and no consistent co-expressed DEGs over three generations. In addition, Cry1F did not obviously alter the expression profiles of seven sensitive biological markers. Our composite data indicates that Cry1F had no long-term harmful effects on collembolan F. candida.

Characterization of a Novel Insecticidal Protein Cry9Cb1 from Bacillus thuringiensis

In recent decades, there have been increasing reports of insect resistance in Bacillus thuringiensis (Bt) crops. Alternative use of Cry toxins, with high insecticidal activity and different mechanisms of action, may be an important strategy to manage this resistance. Cry9 protein, with high toxicity to the lepidopteran pests and no cross-resistance with commercial Cry1 proteins, is a valuable relevant resource. A novel insecticidal protein, MP1489, subsequently named as Cry9Cb1, with 88% amino acid sequence identity with Cry9Ca1, was identified from Bt strain SP663; it exhibited high insecticidal activity against Plutella xylostella, Ostrinia furnacalis, and Chilo suppressalis and no cross-resistance with Cry1Fa in Ostrinia furnacalis. Its minimal active fragments against Plutella xylostella and Ostrinia furnacalis were identified to be 72^T-657^V and 68^D-655^A, respectively; food-safety assessment showed no sequence homology with any known allergen and rapid degradation and inactivation by both heat and the gastrointestinal environment. Therefore, Cry9Cb1 is proposed to have a brilliant prospect as an insecticidal protein in agriculture.

Effects of straw leachates from Cry1C-expressing transgenic rice on the development and reproduction of Daphnia magna

The transgenic rice line T1C-19 provides high resistance to lepidopteran pests because of the synthesis of the Bacillus thuringiensis (Bt) insecticidal protein Cry1C. It thus shows good prospect for commercial planting in China. Species of Cladocera, an order of aquatic arthropods commonly found in aquatic ecosystems such as rice paddies, might be exposed to the insecticidal protein released from Bt-transgenic rice-straw residues. For the study reported herein, we used Daphnia magna (water flea) as a representative of Cladocera to evaluate whether aquatic arthropods are adversely affected when exposed to Bt rice-straw leachates. We exposed D. magna to M4 medium containing various volume percentages of medium that had been incubated with T1C-19 rice straw or rice straw from its non-transformed near-isoline Minghui 63 (MH63) for 21 days. Compared with pure M4 medium (control), the fitness and developmental and reproduction parameters of D. magna decreased significantly when exposed to rice-straw leachates; conversely, no significant differences between the T1C-19 and MH63 rice-straw leachate treatments were observed, indicating that the Bt rice straw leachate did not adversely affect this non-target species.