Does long-term Bt rice planting pose risks to spider communities and their capacity to control planthoppers?

Influence of Cry1Ab protein on growth and development of a predatory spider, Pardosa pseudoannulata, from protective perspectives

The expression of Cry proteins in genetically modified rice varieties safeguards the crop from lepidopteran pests. These proteins have the potential to be transferred through the food chain to arthropods like planthoppers and predatory spiders, triggering defensive responses in these unintended organisms. Hence, we hypothesized that Cry protein might influence the growth and development of spiders by altering protective enzyme activities. The results showed that Cry1Ab protein could accumulate in tissues and subcellular organelles of Pardosa pseudoannulata from Nilaparvata lugens. Cry1Ab protein exposure prolonged the developmental duration in the 5th and 7th instar spiderlings but induced no alterations of other growth indicators, such as body length, median ocular area, and survival rate. In addition, Cry1Ab protein exerted no adverse impacts on several detoxifying enzymes (i.e., superoxide dismutase, catalase, glutathione peroxidase, and acetylcholine esterase) in muscle, midgut, ganglia, and hemolymph at subcellular components (i.e., microsome and cytoplasm). To further explore the effects of Cry1Ab protein on the spiderlings, we performed an integrated transcriptome analysis on spiderlings exposed to Cry1Ab protein. The results showed that Cry1Ab protein might prolong the development duration of P. pseudoannulata via the altered cuticle metabolism (e.g., chitin metabolic process and structural constituent of cuticle). In addition, the gene expression profile associated with detoxifying enzymes and three stress-responsive pathways (JAK/STAT, JNK/SAPK, and Hippo pathways) also displayed no significant alterations under Cry1Ab exposure. Collectively, this integrated analysis generates multidimensional insights to assess the effects of Cry1Ab protein on non-target spiders and demonstrates that Cry1Ab protein exerts no toxicity in P. pseudoannulata.

Monitoring reduced accumulation and risk evaluation of Cry1Ca during food chain transfer from genetically engineered plant to endoparasitoid

BACKGROUND

The potential risk of insecticidal proteins produced by genetically engineered (GE) plants to nontarget organisms have long been an ecotoxicological concern. Apanteles chilonis, an important endoparasitoid of rice pest Chilo suppressalis, potentially is exposed to Bacillus thuringiensis (Bt) endotoxins through a food chain of transgenic Bt rice - C. suppressalis - A. chilonis, and thus, a rigorous risk assessment is urgently needed. Here, we combined a tri-trophic bioassay system with high-dose exposure approach using C. suppressalis hemolymph as the carrier of insecticidal protein to evaluate the biosafety of Cry1Ca to A. chilonis.

RESULTS

Cry1Ca protein could be transmitted and retained along the food chain and remains bioactive in the hemolymph of C. suppressalis during the pre-adult duration of A. chilonis. No significant differences in pre-adult period, male and female longevity, adult fecundity and weight, emergence rate nor sex ratio were observed when A. chilonis parasitized C. suppressalis feeding on cry1Ca rice compared with control treatment. However, the pupal period and weight were significantly prolonged and decreased. When A. chilonis parasitized C. suppressalis injected with a high dosage of Cry1Ca protein, no adverse effects on the life-history parameters, peroxidase (POD), superoxide dismutase (SOD) or glutathione reductase (GR) of A. chilonis were observed, demonstrating that the host quality mediates adverse effects during the food chain.

CONCLUSIONS

We confirmed that Cry1Ca posed no ecological risk to the nontarget endoparasitoid A. chilonis. This study may serve as an example for future risk assessment of transgenic crops to nontarget endoparasitoids. © 2023 Society of Chemical Industry.

Impact of Transgenic Cry1Ab/2Aj Maize on Abundance of Non-Target Arthropods in the Field

Transgenic Bacillus thuringiensis (Bt) maize has broad prospects for application in China. Before commercialization, it is necessary to assess possible ecological impacts, including impacts on non-target arthropods (NTAs) in the field. In the present study, transgenic Bt maize expressing cry1Ab/2Aj and its corresponding non-transformed near isoline were planted under the same environmental and agricultural conditions, and arthropods in the field were collected during the three main growth stages of maize. In a one year trial, the results showed the composition of NTA communities in the transgenic and control maize fields were similar. There were no significant differences for community-level parameters of species richness (S), Shannon-Wiener diversity index (H'), evenness index (J) and Simpson's dominant concentration (C) between the two types of maize fields. Likewise, a Bray-Curtis dissimilarity and distance analysis showed that Cry1Ab/2Aj toxin exposure did not increase community dissimilarities between Bt and non-Bt maize plots and that the structure of the NTAs community was similar on the two maize varieties. Furthermore, planting of the transgenic cry1Ab/2Aj maize did not affect the density or composition of non-target decomposers, herbivores, predators, parasitoids and pollinator guilds. In summary, our results showed that planting of Bt maize producing Cry1Ab/Cry2Aj proteins do not adversely affect population dynamics and diversity of NTAs.

Toxic effects of the combined cadmium and Cry1Ab protein exposure on the protective and transcriptomic responses of Pirata subpiraticus

Cadmium (Cd) pollution poses a serious threat to agricultural production and paddy field fauna. Crystalline proteins (e.g., Cry1Ab and Cry1Ac) are secreted by Bacillus thuringiensis, which can manage pests via a complicated toxic mechanism and have been widely used for pest control due to the commercialization of transgenic crops (e.g., cotton and rice) that expresses Bt insecticidal proteins. Nonetheless, studies on the effects of combined stress of Cd and Cry1Ab protein on field indicator species are limited. In the present study, we showed that spiders, Pirata subpiraticus, fed with Cd-containing flies+Cry1Ab had dramatically higher Cd accumulation than that in the spiders fed with Cd-containing flies (p < 0.05). In addition, the enrichment of Cd led to the activation of the protective mechanism by elevating the concentrations of glutathione peroxidase, glutathione S-transferase, and metallothionein in the spiders (p < 0.05). An in-depth transcriptome analysis revealed that the activities of ion metal binding proteins, transporters, and channels might play essential roles in the Cd accumulation process. More importantly, the higher Cd concentration in the combined Cd+Cry1Ab exposure prolonged developmental duration of P. subpiraticus, due to the down-regulated cuticle proteins (CPs) encoding genes involved in the molting process, which was regulated by a series of putative transcriptional factors such as ZBTB and zf-C2H2. Collectively, this integrated analysis illustrates that the combined Cd+Cry1Ab exposure increases the adverse effects of Cd stress on the growth, antioxidase, and CPs encoding genes of P. subpiraticus, thus providing a research basis and prospect for the rationality of transgenic Cry1Ab crops in the cultivation of heavy metal contaminated soil.