Field performance of transgenic elite commercial hybrid rice expressing bacillus thuringiensis delta-endotoxin

Expression of hybrid fusion protein (Cry1Ac::ASAL) in transgenic rice plants imparts resistance against multiple insect pests

To evolve rice varieties resistant to different groups of insect pests a fusion gene, comprising DI and DII domains of Bt Cry1Ac and carbohydrate binding domain of garlic lectin (ASAL), was constructed. Transgenic rice lines were generated and evaluated to assess the efficacy of Cry1Ac::ASAL fusion protein against three major pests, viz., yellow stem borer (YSB), leaf folder (LF) and brown planthopper (BPH). Molecular analyses of transgenic plants revealed stable integration and expression of the fusion gene. In planta insect bioassays on transgenics disclosed enhanced levels of resistance compared to the control plants. High insect mortality of YSB, LF and BPH was observed on transgenics compared to that of control plants. Furthermore, honeydew assays revealed significant decreases in the feeding ability of BPH on transgenic plants as compared to the controls. Ligand blot analysis, using BPH insects fed on cry1Ac::asal transgenic rice plants, revealed a modified receptor protein-binding pattern owing to its ability to bind to additional receptors in insects. The overall results authenticate that Cry1Ac::ASAL protein is endowed with remarkable entomotoxic effects against major lepidopteran and hemipteran insects. As such, the fusion gene appears promising and can be introduced into various other crops to control multiple insect pests.

Downregulation of Chilo suppressalis alkaline phosphatase genes associated with resistance to three transgenic Bacillus thuringiensis rice lines

Insecticidal crystal (Cry) proteins produced by the bacterium Bacillus thuringiensis are highly toxic to lepidopteran pests. Strains of transgenic rice expressing cry genes have been developed that are resistant to rice pests. Understanding the mode of action of Cry toxins in rice pests will improve our ability to use them effectively as insecticides. In this study, we tested the hypothesis that alkaline phosphatases (ALPs) are involved in Cry1A, Cry2Aa and Cry1Ca toxicity in Chilo suppressalis, an important insect pest of rice crops in China. We first cloned three novel C. suppressalis alps (Csalps) from the larval midgut of C. suppressalis. RNA interference knockdown of six different Csalp genes (Csalp1, Csalp2, Csalp3, Csalp4, Csalp5 and Csalp6) showed that knockdown of three of these, Csalp1, Csalp2 and Csalp4, reduced larval mortality to the transgenic rice strain TT51, which expresses a fusion protein of Cry1Ab and Cry1Ac, whereas suppression of Csalp1, Csalp2, Csalp3, Csalp4 and Csalp6 transcripts decreased the susceptibility of larvae to the transgenic rice strain T2A-1, which expresses cry2Aa. Moreover, downregulation of Csalp1, Csalp2, Csalp3, Csalp4 and Csalp5 transcripts conferred significant tolerance to the transgenic rice strain T1C-19, which expresses cry1Ca. These results suggest that these ALPs play a key role in the toxicity of Cry1A, Cry2A and Cry1C to C. suppressalis.

Bt Jute Expressing Fused δ-Endotoxin Cry1Ab/Ac for Resistance to Lepidopteran Pests

Jute (Corchorus sp.) is naturally occurring, biodegradable, lignocellulosic-long, silky, golden shiny fiber producing plant that has great demands globally. Paper and textile industries are interested in jute because of the easy availability, non-toxicity and high yield of cellulosic biomass produced per acre in cultivation. Jute is the major and most industrially used bast fiber-producing crop in the world and it needs protection from insect pest infestation that decreases its yield and quality. Single locus integration of the synthetically fused cry1Ab/Ac gene of Bacillus thuringiensis (Bt) in Corchorus capsularis (JRC 321) by Agrobacterium tumefaciens-mediated shoot tip transformation provided 5 potent Bt jute lines BT1, BT2, BT4, BT7 and BT8. These lines consistently expressed the Cry1Ab/Ac endotoxin ranging from 0.16 to 0.35 ng/mg of leaf, in the following generations (analyzed upto T4). The effect of Cry1Ab/Ac endotoxin was studied against 3 major Lepidopteran pests of jute- semilooper (Anomis sabulifera Guenee), hairy caterpillar (Spilarctia obliqua Walker) and indigo caterpillar (Spodoptera exigua Hubner) by detached leaf and whole plant insect bioassay on greenhouse-grown transgenic plants. Results confirm that larvae feeding on transgenic plants had lower food consumption, body size, body weight and dry weight of excreta compared to non-transgenic controls. Insect mortality range among transgenic feeders was 66-100% for semilooper and hairy caterpillar and 87.50% for indigo caterpillar. Apart from insect resistance, the transgenic plants were at par with control plants in terms of agronomic parameters and fiber quality. Hence, these Bt jutes in the field would survive Lepidopteran pest infestation, minimize harmful pesticide usage and yield good quality fiber.

High-throughput Sequencing-based Analysis of the Intestinal Microbiota of Broiler Chickens Fed Genetically Modified Rice Expressing Cry1Ac/Cry1Ab Chimeric Bacillus thuringiensis Protein

Many types of Bacillus thuringiensis (Bt)-crops are being grown worldwide, triggering concerns about their potential impact on humans and livestock. To ensure better yield and food safety in China, an attempt has been made to develop Bt-rice targeting a broad range of insects. We aimed to investigate whether feeding genetically modified rice expressing the Bt chimeric Cry1Ac/Cry1Ab protein has any effects on the intestinal microbiota of broilers. Broilers were fed either Bt-rice or its unmodified isogenic parent line for 42 days, and total DNA was isolated from cecum contents for high-throughput sequencing of the 16S rRNA gene. In total, 1,241,005 reads, assigned to 12 phyla, 31 families, and 48 genera were generated. No significant differences were observed in the relative abundance of organisms identified among the major phyla, families, and genera, except for two less abundant families, Thermoanaerobacteraceae and Peptostreptococcaceae, and two less abundant genera, Anaerotruncus and Gelria. The results were in agreement with those from culture-based analysis and Biolog EcoPlates. These results illustrate that feeding Bt-rice has no adverse effects on the broiler intestinal microbiota and provide sufficient support for the food safety of Bt-rice.

Long-term cultivation of Bt rice expressing the Cry1Ab/1Ac gene reduced phytoparasitic nematode abundance but did not affect other nematode parameters in paddy fields

The uncertainty of ecological risks and the effects of growing transgenic Bt rice on the environment hamper its commercial production. Here, soil nematode communities were used as an indicator of soil health and soil food web structure to evaluate the potential effects of growing Bt rice without chemical insecticides for 3years in the paddy field. The nematodes and soil physicochemical properties of Bt rice fields were compared to the near-isogenic control, non-Bt rice fields. A total of 108,363 specimens belonging to 28 different genera were enumerated. The Hirschmanniella, Tobrilus, Dorylaimus and Filenchus were dominant genera. A three-year paddy rice cultivation of Bt rice (Huahui 1) negatively affected the abundance of phytoparasitic nematodes but did not affect the total number of nematodes, the abundance and relative abundance of free-living nematodes, genera richness, diversity indices, soil food web conditions, or community compositions. However, apparent seasonal and inter-annual changes in these variables were observed, indicating that the impact of environmental factors was more stronger than that of the Bt toxin. In conclusion, the potential ecological risks of Bt rice on soil health and sustainability warrant further research to disentangle the impacts from various confounding environmental factors.

Development of Monoclonal Antibodies Recognizing Linear Epitope: Illustration by Three Bacillus thuringiensis Crystal Proteins of Genetically Modified Cotton, Maize, and Tobacco

Bacillus thuringiensis Cry1Ac, Cry1Ia1, and Cry1Ie are δ-endotoxin insecticidal proteins widely implemented in genetically modified organisms (GMO), such as cotton, maize, and potato. Western blot assay integrates electrophoresis separation power and antibody high specificity for monitoring specific exogenous proteins expressed in GMO. Procedures for evoking monoclonal antibody (mAb) for Western blot were poorly documented. In the present study, Cry1Ac partially denatured at 100 °C for 5 min was used as an immunogen to develop mAbs selectively recognizing a linear epitope of Cry1Ac for Western blot. mAb 5E9C6 and 3E6E2 selected with sandwich ELISA strongly recognized the heat semidenatured Cry1Ac. Particularly, 3E6E2 recognized both E. coli and cotton seed expressed Cry1Ac in Western blot. Such strategy of using partially denatured proteins as immunogens and using sandwich ELISA for mAb screening was also successfully demonstrated with production of mAbs against Cry1Ie for Western blot assay in maize.

Application of Cre-lox gene switch to limit the Cry expression in rice green tissues

The presence of genetically modified (GM) protein in the endosperm is important information for the public when considering the biological safety of transgenic rice. To limit the expression of GM proteins to rice green tissues, we developed a modified Cre-lox gene switch using two cassettes named KEY and LOCK. KEY contains a nuclear-localized Cre recombinase driven by the green-tissue-specific promoter rbcS. LOCK contains a Nos terminator (NosT), which is used to block the expression of the gene of interest (GOI), bounded by two loxP sites. When KEY and LOCK are pyramided into hybrid rice, a complete gene switch system is formed. The Cre recombinase from KEY excises loxP-NosT in LOCK and unlocks the GOI in green tissues but keeps it locked in the endosperm. This regulatory effect was demonstrated by eYFP and Bt expression assays. The presence of eYFP and Cre were confirmed in the leaf, sheath, stem, and glume but not in the root, anther or seed of the gene-switch-controlled eYFP hybrids. Meanwhile, gene switch-controlled Bt hybrid rice not only confined the expression of Bt protein to the green tissues but also showed high resistance to striped stem borers and leaffolders.

Effects of Transgenic Rice Infected with SRBSDV on Bt expression and the Ecological Fitness of Non-vector Brown Planthopper Nilaparvata lugens

The susceptibility of rice lines, T1C-19, T2A-1, and MH63 to SRBSDV infection are similar and the contents of cry protein in T2A-1 and T1C-19 do not change significantly. The survival rates of BPH nymphs feeding on SRBSDV-infected T1C-19, Bt T2A-1, or MH63 rice plants were not significantly different. The developmental stages of female BPH fed on T1C-19 plants infected with SRBSDV were significantly shorter than those fed on uninfected rice, while the males showed no significant difference. The duration of BPH feeding on SRBSDV-infected T2A-1 and MH63 also showed no significant difference in comparison with the respective control groups. Longevities of BPH adults feeding on SRBSDV-infected T1C-19, T2A-1 or MH63 were also not significant. However, the longevity of male adult BPH feeding on un-infected MH63 was significantly reduced in comparison with that of adult males feeding on un-infected T1C-19 and T2A-1 rice. In addition, the different rice lines and the rice plants infected and uninfected with SRBSDV did not significantly affect the sex ratio, female body weight, longevity, fecundity, or egg hatchability of BPH. In general, transgenic Bt rice infected with SRBSDV had little effect on the ecological adaptability of BPH.

No effect of Bt-transgenic rice litter on the meiobenthos community in field ditches

BACKGROUND

The non-target effect of Bacillus thuringiensis (Bt) toxins in aquatic ecosystems is crucial to improve the present assessment of Bt-transgenic plants, particularly where crops are cultivated near aquatic ecosystems. We conducted decomposition experiments during two growing seasons to determine the effects of Bt-transgenic rice litter with and without insecticide application on the meiobenthos communities in a field ditch.

RESULTS

The community composition of meiobenthos colonised on leaf litter was not significantly different between Bt and non-Bt rice. The abundance of meiobenthos colonising leaves differed between insecticide application and control, and this insecticide effect interacted with rice type. No Bt toxin was detected in field ditch water. Leaf decomposition and nutrient content were comparable for both Bt and non-Bt rice with or without insecticide application.

CONCLUSION

Bt-transgenic rice litter had no effect on the meiobenthos community composition in field ditches, but the chronic persistence of transgenic litter in nature needs to be taken into account at large scales in aquatic ecosystems. © 2016 Society of Chemical Industry.

Transgenic Bt rice lines producing Cry1Ac, Cry2Aa or Cry1Ca have no detrimental effects on Brown Planthopper and Pond Wolf Spider

Transgenic rice expressing cry genes from the bacterium Bacillus thuringiensis (Bt rice) is highly resistant to lepidopteran pests. The brown planthopper (BPH, Nilaparvata lugens) is the main non-target sap-sucking insect pest of Bt transgenic rice. The pond wolf spider (PWS, Pardosa pseudoannulata) is one of the most dominant predators of BPH in rice fields. Consequently, the safety evaluation of Bt rice on BPH and PWS should be conducted before commercialization. In the current study, two experiments were performed to assess the potential ecological effects of Bt rice on BPH and PWS: (1) a tritrophic experiment to evaluate the transmission of Cry1Ac, Cry2Aa and Cry1Ca protein in the food chain; and (2) binding assays of Cry1Ac, Cry2Aa and Cry1Ca to midgut brush border membrane proteins from BPH and PWS. Trace amounts of the three Cry proteins were detected in BPH feeding on Bt rice cultivars, but only Cry1Ac and Cry2Aa proteins could be transferred to PWS through feeding on BPH. In vitro binding of biotinylated Cry proteins and competition assays in midgut protein vesicles showed weak binding, and ligand blot analysis confirmed the binding specificity. Thus, we inferred that the tested Bt rice varieties have negligible effects on BPH and PWS.

Successful detection of foreign inserts in transgenic rice TT51-1 (BT63) by RNA-sequencing combined with PCR

BACKGROUND

As event-specific sequence information for most unauthorised genetically modified organisms (GMOs) is currently still unavailable, detecting unauthorised GMOs remains challenging. Here, we used insect-resistant rice TT51-1 as an example to develop a novel approach via detecting GMOs by RNA-seq (sequencing) and PCR. RNA-seq of TT51-1 generated 4.8 million (M) 21-nt cDNA tags. Alignment to the Oryza sativa subsp. japonica reference genome revealed 24 098 unmapped tags. Foreign tags from the nopaline synthetic enzyme gene (NOS) terminator and insect-resistant genes were then identified by searching against the NCBI VecScreen and NT databases.

RESULTS

To further isolate foreign DNA sequences, putative NOS terminator and insect-resistant gene tags were combined and used directly as primer pairs for long-range PCR, producing a 5016-bp fragment. The inserted DNA sequence of TT51-1 has been submitted to a database, and thus, similarity analysis using the database could identify a test sample.

CONCLUSION

The novel approach has a great potential for application to the detection and identification of unauthorised GMOs in food and feed products. © 2016 Society of Chemical Industry.

The tiered-evaluation of the effects of transgenic cry1c rice on Cyrtorhinus lividipennis, a main predator of Nilaparvata lugens

T1C-19, a newly developed transgenic cry1C rice line, expresses cry1C under the control of the maize ubiquitin promoter, and is highly resistant to lepidopteran pests of rice. Cyrtorhinus lividipennis is the major predator of the eggs and young nymphs of Nilaparvata lugens, which is the main non-target sap-sucking insect pest of Bt rice. C. lividipennis may be exposed to Cry1C protein, thus biosafety evaluations of transgenic cry1C rice on C. lividipennis should be conducted before the commercialization of T1C-19. In the current study, we tested the direct toxicity of elevated doses of Cry1C to C. lividipennis, effects of T1C-19 on the life-table parameters of C. lividipennis via preying planthoppers, and effects of T1C-19 on the population density and dynamics in rice fields. No detrimental effects on development, survival, female ratio and body weight of C. lividipennis were caused by direct exposure to elevated doses of the Cry1C protein or prey-mediated exposure to realistic doses of the protein. The population density and dynamics did not significantly differ between C. lividipennis in T1C-19 and non-transgenic rice fields. Thus, transgenic cry1C rice had no negative effects on C. lividipennis. This is the first report of the effects of transgenic cry1C rice on C. lividipennis.

Marker assisted pyramiding of two brown planthopper resistance genes, Bph3 and Bph27 (t), into elite rice Cultivars

BACKGROUND

Brown planthopper (BPH) is the most destructive insect in rice production. Breeding of resistant cultivars is the most cost-effective and environment-friendly strategy for BPH management; however, resistant cultivars are currently hampered by the rapid breakdown of BPH resistance. Thus, there is an urgent need to use more effective BPH resistance genes or pyramiding different resistance genes to develop more durable resistant rice cultivars.

RESULTS

Here a dominant BPH resistance gene Bph27(t) were introgressed into a susceptible commercial japonica variety Ningjing3 (NJ3) and indica variety 93-11 using marker-assisted selection (MAS), respectively. Further, Bph27(t) and a durable BPH resistance gene Bph3 was pyramided by intercrossing single-gene introgressed lines through MAS. The introgression of BPH resistance genes significantly improved the BPH resistance and reduced the yield loss caused by BPH.

CONCLUSION

The development of single and two genes pyramided lines in this study provides innovative resources for molecular breeding of durable BPH-resistant rice cultivars and BPH management through resistant cultivars.

RNAi in the striped stem borer, Chilo suppressalis, establishes a functional role for aminopeptidase N in Cry1Ab intoxication

The striped stem borer, Chilo suppressalis, is a major target pest of transgenic rice expressing the Cry1Ab protein from the bacterium Bacillus thuringiensis (Bt) in China. Evolution of resistance in this pest is a major threat to the durability of Bt rice. Since Bt exerts its activity through binding to specific receptors in the midgut of target insects, identification of functional Cry1Ab receptors in the midgut of C. suppressalis larvae is crucial to evaluate potential resistance mechanisms and develop effective strategies for delaying insect resistance. In this work, we identified the putative Cry1Ab toxin-binding protein, aminopeptidase-N (APN), in the midgut of C. suppressalis by ligand blot and mass spectrometry. After cloning the full-length cDNAs encoding APN isoforms from the C. suppressalis larval midgut, we studied their spatiotemporal expression in different gut tissues and developmental stages. Furthermore, RNA interference (RNAi) against C. suppressalis aminopeptidases (CsAPNs) was employed to illustrate a functional role for CsAPNs in Cry1Ab toxicity to C. suppressalis larvae using injection and oral delivery of Stealth™ siRNA. Down-regulating the expression of CsAPNs by RNAi was closely associated with reduced susceptibility of C. suppressalis to Cry1Ab. These data provide the first direct evidence that CsAPNs participate in the mode of Cry1Ab action and may act as the functional receptor of Cry1A in C. suppressalis larvae.

Development of Bt Rice and Bt Maize in China and Their Efficacy in Target Pest Control

Rice and maize are important cereal crops that serve as staple foods, feed, and industrial material in China. Multiple factors constrain the production of both crops, among which insect pests are an important one. Lepidopteran pests cause enormous yield losses for the crops annually. In order to control these pests, China plays an active role in development and application of genetic engineering (GE) to crops, and dozens of GE rice and GE maize lines expressing insecticidal proteins from the soil bacterium Bacillus thuringiensis (Bt) have been developed. Many lines have entered environmental release, field testing, and preproduction testing, and laboratory and field experiments have shown that most of the Bt rice and Bt maize lines developed in China exhibited effective control of major target lepidopteran pests on rice (Chilo suppressalis, Scirpophaga incertulas, and Cnaphalocrocismedinalis) and maize (Ostrinia furnacalis), demonstrating bright prospects for application. However, none of these Bt lines has yet been commercially planted through this writing in 2016. Challenges and perspectives for development and application of Bt rice and maize in China are discussed. This article provides a general context for colleagues to learn about research and development of Bt crops in China, and may shed light on future work in this field.

Genetically modified rice Bt-Shanyou63 expressing Cry1Ab/c protein does not harm Daphnia magna

The genetically modified (GM) rice Bt-ShanYou63 (Bt-SY63) received an official biosafety certificate while its safety remained in dispute. In a lifelong study, Daphnia magna were experimentally fed a basal diet of rice flours from Bt-SY63 or its parental rice ShanYou63 (SY63) at concentrations of 0.2mg, 0.3mg, or 0.4mgC (per individual per day). Overall the survival, body size, and reproduction of the animals were comparable between Bt-SY63 and ShanYou63.. The results showed that no significant differences were observed in growth and reproduction parameters between D. magna fed GM and non-GM flour and no dose-related changes occurred in all the values. Based on the different parameters assessed, the GM rice Bt-SY63 is a safe food source for D. magna that does not differ in quality from non-GM rice.

Effects of Bt-transgenic rice cultivation on planktonic communities in paddy fields and adjacent ditches

The non-target effects of transgenic plants are issues of concern; however, their impacts in cultivated agricultural fields and adjacent natural aquatic ecosystems are poorly understood. We conducted field experiments during two growing seasons to determine the effects of cultivating Bacillus thuringiensis (Bt)-transgenic rice on the phytoplankton and zooplankton communities in a paddy field and an adjacent ditch. Bt toxin was detected in soil but not in water. Water quality was not significantly different between non-Bt and Bt rice fields, but varied among up-, mid- and downstream locations in the ditch. Cultivation of Bt-transgenic rice had no effects on zooplankton communities. Phytoplankton abundance and biodiversity were not significantly different between transgenic and non-transgenic rice fields in 2013; however, phytoplankton were more abundant in the transgenic rice field than in the non-transgenic rice field in 2014. Water quality and rice type explained 65.9% and 12.8% of this difference in 2014, respectively. Phytoplankton and zooplankton were more abundant in mid- and downstream, than upstream, locations in the ditch, an effect that we attribute to water quality differences. Thus, the release of Bt toxins into field water during the cultivation of transgenic crops had no direct negative effects on plankton community composition, but indirect effects that alter environmental conditions should be taken into account during the processes of management planning and policymaking.

Pyramiding and evaluation of both a foreign Bacillus thuringiensis and a Lysine-rich protein gene in the elite indica rice 9311

Gene pyramiding is an efficient approach for the genetic improvement of multiple agronomic traits simultaneously. In this study, we pyramided two foreign genes, cry1Ac driven by the rice Actin I promoter, and lysine-rich protein (LRP), driven by the endosperm-specific GLUTELIN1 (GT1) promoter, into the elite indica cultivar 9311. These two genes were chosen in an attempt to enhance insect-resistance and Lysine (Lys) content. In the pyramided line, the foreign gene cry1Ac was efficiently expressed in the leaves and stems, and exhibited highly efficient resistance to striped stem borer (SSB, Chilo suppressalis Walker) in the laboratory and rice leaf folder (RLF, Cnaphalocrocis medinalis Guenee) in the field. Furthermore, the LRP gene was highly expressed in the endosperm and produced a remarkable increase of Lys content in the seeds of the pyramided line. The data from field trials demonstrated that most of the agronomic traits including yield were well maintained in the pyramided line compared to the parental control. These results strongly suggest that the foreign cry1Ac and LRP genes have remarkable application potential in rice, and the resultant pyramided line serves as an ideal bridge material for the improvement of insect-resistance and high Lys rice in the future.

Potential resistance management for the sustainable use of insect-resistant genetically modified corn and rice in China

Many lines of insect-resistant genetically modified (IRGM) corn and rice containing Bacillus thuringiensis (Bt) insecticidal genes have been developed and undergone different environmental biosafety assessments stages in China, showing robust application prospects. The potential of targeted pests to develop resistance to Bt crops is widespread, which threatens the sustainable utility of IRGM corn and rice. In this study, the potential risks of target pest complexes developing resistance to IRGM corn and rice are evaluated. Theoretical and empirical studies implementing precautionary insect resistance management (IRM) strategies to delay resistance evolution are summarized and challenges to IRM are discussed. Additionally, solutions facing these challenges are proposed. Finally, directions for future studies in developing IRGM corn and rice and IRM plans are discussed.

Both overexpression and suppression of an Oryza sativa NB-LRR-like gene OsLSR result in autoactivation of immune response and thiamine accumulation

Tight and accurate regulation of immunity and thiamine biosynthesis is critical for proper defence mechanisms and several primary metabolic cycles in plants. Although thiamine is known to enhance plant defence by priming, the mechanism by which thiamine biosynthesis responds to immune signals remains poorly understood. Here we identified a novel rice (Oryza sativa L.) NB-LRR gene via an insertion mutation, this mutant confesses a low seed setting phenotype and the corresponding genetic locus was named OsLSR (Low seed setting related). Comparing with wildtype plant, both overexpression and suppression of OsLSR lead to the autoactivation of the rice immune system and accumulation of thiamine, which result in a great fitness cost and yield penalty. Moreover, when fused with eGFP at their C terminus, two fragments, OsLSR1-178 and OsLSR464-546, localized to chloroplasts where thiamine is produced. Our result suggests that OsLSR differs from traditional NB-LRR genes. Its expression is closely related to the immune status and thiamine level in plant cells and should be maintained within a narrow range for rice growth.

The New Transgenic cry1Ab/vip3H Rice Poses No Unexpected Ecological Risks to Arthropod Communities in Rice Agroecosystems

The ecological risks to nontarget organisms should be rigorously assessed before Bt crops are released. Here, the impacts of a new Cry1Ab/Vip3H rice line on arthropod communities in rice agroecosystems were evaluated across 3 yr. Arthropods collected via vacuum were sorted into five guilds. The abundance and proportion of each guild as well as community-level parameters were determined in Cry1Ab/Vip3H and control rice fields. Changes in arthropod species assemblage over sampling dates were investigated by principal response curves (PRCs). Cry1Ab/Vip3H rice did not exert significant impacts on the seasonal density and proportion of each guild, except parasitoids. Detritivore seasonal density, but not its relative abundance, was significantly affected by Cry1Ab/Vip3H rice. Four community indices (species richness S, Shannon-Wiener index H', Simpson index D, and evenness index J') were similar between rice types. PRCs revealed a slight community difference between rice types in the past two tested years, with rice types accounting for 1.0-3.5% of the variance among arthropod communities. However, sampling dates explain 32.1-67.6% for these community differences. Of the 46 taxa with higher species weights, 26.1% of the taxa were significantly different, including seven taxa with higher abundance and five with lower density in Cry1Ab/Vip3H rice fields. These differences may be attributed to change in abundance of prey or hosts but not to direct effects of Bt proteins. We infer that this new Cry1Ab/Vip3H rice line poses no unintended ecological risks to the arthropod community.

The development and status of Bt rice in China

Multiple lines of transgenic rice expressing insecticidal genes from the bacterium Bacillus thuringiensis (Bt) have been developed in China, posing the prospect of increases in production with decreased application of pesticides. We explore the issues facing adoption of Bt rice for commercial production in China. A body of safety assessment work on Bt rice has shown that Bt rice poses a negligible risk to the environment and that Bt rice products are as safe as non-Bt control rice products as food. China has a relatively well-developed regulatory system for risk assessment and management of genetically modified (GM) plants; however, decision-making regarding approval of commercial production has become politicized, and two Bt rice lines that otherwise were ready have not been allowed to enter the Chinese agricultural system. We predict that Chinese farmers would value the prospect of increased yield with decreased use of pesticide and would readily adopt production of Bt rice. That Bt rice lines may not be commercialized in the near future we attribute to social pressures, largely due to the low level of understanding and acceptance of GM crops by Chinese consumers. Hence, enhancing communication of GM crop science-related issues to the public is an important, unmet need. While the dynamics of each issue are particular to China, they typify those in many countries where adoption of GM crops has been not been rapid; hence, the assessment of these dynamics might inform resolution of these issues in other countries.

A Comprehensive Assessment of the Effects of Transgenic Cry1Ac/Cry1Ab Rice Huahui 1 on Adult Micraspis discolor (Fabricius) (Coleoptera: Coccinellidae)

Micraspis discolor (Fabricius) (Coleoptera: Coccinellidae) is a widely distributed coleoptera predator in southern Asia in rice ecosystem, and adult M. discolor feed on both rice pollen and soft-bodied arthropods. Bitrophic bioassay and tritrophic bioassay were conducted to evaluate the potential impact of Cry1Ac/Cry1Ab-expressing rice Huahui 1 and its non-transgenic counterpart Minghui 63 on fitness parameters of adult M. discolor. The results showed that the survival, and fecundity of this beetle’ adults were not different when they fed on Bt rice or non-Bt rice pollen or Nilaparvata lugens (Stål) reared on Bt rice or non-Bt rice. Toxicity assessment to ensure M. discolor adults were not sensitive to Cry1Ab or Cry1Ac protein independent from the pollen background, M. discolor adults were fed with an artificial diet containing Cry1Ac, Cry1Ab or both protein approximately 10 times higher concentration than in Huahui 1 rice pollen. No difference was detected for any of the life-table parameters tested between Cry protein-containing and pure diet. Artificial diet containing E-64 (N-(trans-Epoxysuccinyl)-L-leucine 4-guanidinobutylamide) was included as a positive control. In contrast, the pre-oviposition and fecundity of M. discolor were significantly adversely affected by feeding on E-64-containing diet. In both bioassays, the uptakes of Cry protein by adult M. discolor were tested by ELISA measurements. These results indicated that adults of M. discolor are not affected by Cry1Ab- or Cry1Ac-expressing rice pollen and are not sensitive to Cry protein at concentrations exceeding the levels in rice pollen in Huahui1. This suggests that M. discolor adults would not be harmed by Cry1Ac/Cry1Ab rice if Bt rice Huahui 1 were commercialized.

Development of leaffolder resistant transgenic rice expressing cry2AX1 gene driven by green tissue-specific rbcS promoter

The insecticidal cry genes of Bacillus thuringiensis (Bt) have been successfully used for development of insect resistant transgenic rice plants. In this study, a novel cry2AX1 gene consisting a sequence of cry2Aa and cry2Ac gene driven by rice rbcS promoter was introduced into a rice cultivar, ASD16. Among 27 putative rice transformants, 20 plants were found to be positive for cry2AX1 gene. The expression of Cry2AX1 protein in transgenic rice plants ranged from 5.95 to 122.40 ng/g of fresh leaf tissue. Stable integration of the transgene was confirmed in putative transformants of rice by Southern blot hybridization analysis. Insect bioassay on T0 transgenic rice plants against rice leaffolder (Cnaphalocrosis medinalis) recorded larval mortality up to 83.33%. Stable inheritance and expression of cry2AX1 gene in T1 progenies was demonstrated using Southern and ELISA. The detached leaf bit bioassay with selected T1 plants showed 83.33-90.00% mortality against C. medinalis. The whole plant bioassay for T1 plants with rice leaffolder showed significant level of resistance even at a lower level of Cry2AX1 expression varying from 131 to 158 ng/g fresh leaf tissue during tillering stage.

Comparison of three transgenic Bt rice lines for insecticidal protein expression and resistance against a target pest, Chilo suppressalis (Lepidoptera: Crambidae)

Two transgenic rice lines (T2A-1 and T1C-19b) expressing cry2A and cry1C genes, respectively, were developed in China, targeting lepidopteran pests including Chilo suppressalis (Walker) (Lepidoptera: Crambidae). The seasonal expression of Cry proteins in different tissues of the rice lines and their resistance to C. suppressalis were assessed in comparison to a Bt rice line expressing a cry1Ab/Ac fusion gene, Huahui 1, which has been granted a biosafety certificate. In general, levels of Cry proteins were T2A-1 > Huahui 1 > T1C-19b among rice lines, and leaf > stem > root among rice tissues. The expression patterns of Cry protein in the rice line plants were similar: higher level at early stages than at later stages with an exception that high Cry1C level in T1C-19b stems at the maturing stage. The bioassay results revealed that the three transgenic rice lines exhibited significantly high resistance against C. suppressalis larvae throughout the rice growing season. According to Cry protein levels in rice tissues, the raw and corrected mortalities of C. suppressalis caused by each Bt rice line were the highest in the seedling and declined through the jointing stage with an exception for T1C-19b providing an excellent performance at the maturing stage. By comparison, T1C-19b exhibited more stable and greater resistance to C. suppressalis larvae than T2A-1, being close to Huahui 1. The results suggest cry1C is an ideal Bt gene for plant transformation for lepidopteran pest control, and T1C-19b is a promising Bt rice line for commercial use for tolerating lepidopteran rice pests.

The fate of fusion Cry1Ab/1Ac proteins from Bt-transgenic rice in soil and water

Toxin proteins form transgenic crops entering into the environment are likely affect non-target organisms. To investigate the entry route and fate of fusion Cry1Ab/1Ac proteins from transgenic rice expressing insecticide toxins from Bacillus thuringiensis (Bt) in soil and water, we conducted greenhouse and field experiments in 2013 and 2014. Cry1Ab/1Ac proteins from Bt-transgenic rice in soil was found within a horizontal range of 25cm, where most of plant roots distributed. Concentration of Cry1Ab/1Ac proteins was lower in water than in soil in the greenhouse experiment, and no Cry1Ab/1Ac protein was detected in field water. Cry1Ab/1Ac concentration from rice straws was higher in ditch water than in distilled water due to the existence of aquatic organisms in ditch water. Bt proteins from transgenic crops enter into soil ecosystems mainly through root exudates and into aquatic ecosystems through plant residues, which determines Bt fate in the environment.

Development of Marker-Free Insect-Resistant Indica Rice by Agrobacterium tumefaciens-Mediated Co-transformation

Agrobacterium-mediated co-transformation is an efficient strategy to generate marker-free transgenic plants. In this study, the vectors pMF-2A^∗ containing a synthetic cry2A^∗ gene driven by maize ubiquitin promoter and pCAMBIA1301 harboring hygromycin phosphotransferase gene (hpt) were introduced into Minghui86 (Oryza sativa L. ssp. indica), an elite indica restorer line. Two independent transformants containing both the cry2A^∗ gene and hpt gene were regenerated. Several homozygous marker-free transgenic progenies were derived from family 2AH2, and three of them were selected for further insect bioassay in the laboratory and field. Insect-resistance assays revealed that all the three transgenic lines were highly resistant to striped stem borer (Chilo suppressalis), yellow stem borer (Tryporyza incertulas) and rice leaf folder (Cnaphalocrocis medinalis). The measurement of Cry2A protein concentration showed that Cry2A protein was stably expressed in leaves and stems of homozygous transgenic lines and their hybrids. The yields of the marker-free homozygous transgenic lines and their hybrids were not significantly different from those of their corresponding controls. Furthermore, the results of flanking sequence isolation showed that the T-DNA in line 8-30 was integrated into the intergenic region of chromosome 2 (between Os02g43680 and Os02g43690). These results indicate that the marker-free transgenic rice has the potential for commercial production.

Chilo suppressalis and Sesamia inferens display different susceptibility responses to Cry1A insecticidal proteins

BACKGROUND

Chilo suppressalis and Sesamia inferens are important lepidopteran rice pests that occur concurrently in rice-growing areas of China. The development of transgenic rice expressing Cry1A insecticidal proteins has provided a useful strategy for controlling these pests.

RESULTS

This study evaluated the baseline susceptibilities of C. suppressalis and S. inferens to Cry1A, as well as their responses to selection with Cry1A. Wide geographic variation in susceptibility was observed across all field populations. Within a given population, the LC50 of both Cry1Ab and Cry1Ac against S. inferens was drastically higher than that of C. suppressalis. Large LC50 differences (74.6-fold) were detected between the two species for Cry1Ab in the Poyang population, while small differences (3.6-fold) were detected for Cry1Ac in the Changsha population. The Cry1Ac LC50 of C. suppressalis and S. inferens increased 8.4- and 4.4-fold after 21 and eight selection generations respectively. Additionally, the estimated realised heritabilities (h(2) ) of Cry1Ac tolerance were 0.11 in C. suppressalis and 0.292 in S. inferens.

CONCLUSIONS

S. inferens exhibited a significantly lower susceptibility and more rapidly evolved resistance to Cry1A compared with C. suppressalis. Therefore, S. inferens is more likely to evolve increased resistance, which threatens the sustainability of rice expressing Cry1A protein.

Transgenic cry1C(⁎) gene rough rice line T1C-19 does not change the host preferences of the non-target stored product pest, Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae), and its parasitoid wasp, Anisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae)

Rough rice grains are often stored for extended periods before they are used or consumed. However, during storage, the rough rice is vulnerable to insect infestation, resulting in significant economic loss. Previous studies have shown that volatiles cues, physical characteristics, and taste chemicals on the grains could be the important key behavior factors for storage insect pests to locate the hosts and select oviposition sites. It is also well known that the transgenic Bt rough rice line T1C-19, which expresses a cry1C(⁎) gene has a high resistance to Lepidoptera pests. However, there were no evidences to show the consequences of host preference for non-target insect pests after growing Bt transgenic rice. In this study, the potential key factors of Bt rough rice were investigated for their impacts on the behaviors of non-target pest lesser grain borer Rhyzopertha dominica, the main weevil pest of grain and its parasitic wasps Anisopteromalus calandrae, the natural enemy of the beetle. Both electronic nose and electronic tongue analyses showed that the parameters of Bt rough rice were analogous to those of the non-Bt rough rice. The volatile profiles of Bt and non-Bt rough rice examined by gas chromatographic mass spectrometry (GC-MS) were similar. For most volatile compounds, there were no significantly quantitative differences in compound quantities between Bt and non-Bt rough rice. The densities of sclereids and trichomes on the rough rice husk surface were statistically equal in Bt and non-Bt rough rice. The non-target pest, R. dominica, and its parasitoid wasp, A. calandrae, were attracted to both rough rice and could not distinguish the transgenic T1C-19 from the isogenic rough rice. These results demonstrated that Bt rough rice has no negative impacts on the host preference behaviors of non-target stored product pest R. dominica and its parasitoid A. calandrae.

Development of photoperiod- and thermo-sensitive male sterility rice expressing transgene Bacillus thuringiensis

Stem borers and leaffolders are the main pests that cause severe damage in rice (Oryza sativa L.) production worldwide. We developed the first photoperiod- and thermo-sensitive male sterility (PTSMS) rice 208S with the cry1Ab/1Ac Bacillus thuringiensis (Bt) gene, through sexual crossing with Huahui 1 (elite line with the cry1Ab/1Ac gene). The novel 208S and its hybrids presented high and stable resistance to stem borers and leaffolders, and the content of Cry1Ab/1Ac protein in chlorophyllous tissues achieved the identical level as donor and showed little accumulation in non-chlorophyllous tissue. No dominant dosage effect in the Bt gene was observed in 208S and its derived hybrids. An analysis of fertility transition traits indicated that 208S was completely sterile under long day length/high temperature, but partially fertile under short day length/low temperature. With fine grain quality and favorable combining ability, 208S had no observed negative effects on fertility and agronomic traits from Bt (cry1Ab/1Ac). Additionally, 208S as a male sterile line showed no fertility decrease caused by Bt transgenic process, as it is the case in Huahui 1. Thus, 208S has great application value in two-line hybrid production for insect resistance, and can also be used as a bridge material in rice Bt transgenic breeding.

Transgenic cry1C or cry2A rice has no adverse impacts on the life-table parameters and population dynamics of the brown planthopper, Nilaparvata lugens (Hemiptera: Delphacidae)

BACKGROUND

Transgenic rice producing the insecticidal protein from Bacillus thuringiensis Berliner (Bt) is protected from damage by lepidopteran insect pests. However, one of the main concerns about Bt rice is the potential impact on non-target herbivores. In the present study, the ecological impacts of two Bt rice lines, T1C-19 expressing Cry1C protein and T2A-1 expressing Cry2A protein, on the non-target herbivore brown planthopper (BPH), Nilaparvata lugens (Stål), were evaluated under laboratory and field conditions. The purpose was to verify whether these Bt rice lines could affect the performance of BPH at individual and population scales.

RESULTS

Laboratory results showed that most of the fitness parameters (development duration, survival rate, fecundity, fertility, amount of honeydew excreted) of BPH were not significantly affected by the two tested Bt rice lines, although the development duration of fourth-instar nymphs fed on T1C-19 was distinctly longer compared with that on T2A-1 and non-Bt rice plants. Five life-table parameters did not significantly differ among rice types. Two-year field trials also revealed no significant difference in population dynamics of BPH among rice types.

CONCLUSION

It is inferred that the tested Bt rice lines are unlikely to affect the population growth of BPH.

Characterization of competitive interactions in the coexistence of Bt-transgenic and conventional rice

BACKGROUND

Transgene flow through pollen and seeds leads to transgenic volunteers and feral populations in the nature, and consumer choice and economic incentives determine whether transgenic crops will be cultivated in the field. Transgenic and non-transgenic plants are likely to coexist in the field and natural habitats, but their competitive interactions are not well understood.

METHODS

Field experiments were conducted in an agricultural ecosystem with insecticide spraying and a natural ecosystem, using Bt-transgenic rice (Oryza sativa) and its non-transgenic counterpart in pure and mixed stands with a replacement series.

RESULTS

Insect damage and competition significantly decreased plant growth and reproduction under the coexistence of transgenic and conventional rice. Insect-resistant transgenic rice was not competitively superior to its counterpart under different densities in both agricultural and natural ecosystems, irrespective of insect infection. Fitness cost due to Bt-transgene expression occurred only in an agroecosystem, where the population yield decreased with increasing percentage of transgenic rice. The population yield fluctuated in a natural ecosystem, with slight differences among pure and mixed stands under plant competition or insect pressure. The presence of Chilo suppressalis infection increased the number of non-target insects.

CONCLUSIONS

Plant growth and reproduction patterns, relative competition ability and population yield indicate that Bt-transgenic and non-transgenic rice can coexist in agroecosystems, whereas in more natural habitats, transgenic rice is likely to outcompete non-transgenic rice.

Loss of Genetic Variation in Laboratory Colonies of Chilo suppressalis (Lepidoptera: Crambidae) Revealed by Mitochondrial and Microsatellite DNA Markers

The Asiatic rice borer, Chilo suppressalis (Walker), is an important insect pest of rice in China. The genetic variation of a set of laboratory colonies of C. suppressalis was compared with their source populations in the wild (laboratory colonies BJCK, BJ1AB, and BJ1AC versus wild population BJW; laboratory colonies FZCK and FZ1CA versus wild population FZW) and was analyzed using eight microsatellite markers and two partial mitochondrial DNA (mtDNA) regions (COI and COII). Results from both analyses revealed similar patterns. Microsatellite DNA analysis showed that the two wild populations (BJW and FZW) harbored more private alleles and had higher levels of gene diversity, and observed and expected heterozygosity, compared with the laboratory colonies. Mitochondrial DNA analysis revealed that the two wild populations (BJW and FZW) had higher numbers of haplotypes compared with the five laboratory colonies. The three Beijing laboratory-reared colonies (BJ1CK, BJ1AB, and BJ1AC) had one fixed haplotype (H04). Most of the pairwise FST values based on mtDNA were high and all pairwise FST comparisons based on microsatellite DNA were significant, which indicated that the significant differences between these colonies and populations. Genetic drift caused by several factors, such as founder effect, small effective population size, rearing protocols, and inbreeding, can contribute to the rapid loss of genetic variation and affect the distribution of alleles and haplotypes. Therefore, it is necessary to increase the sample size of source populations to prevent the loss of genetic variation and genetic differentiation between different colonies.

The effects of triazophos applied to transgenic Bt rice on the nutritional indexes, Nlvg expression, and population growth of Nilaparvata lugens Stål under elevated CO₂

The brown planthopper, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae), is a typical pest in which population resurgence can be induced by insecticides. Warmer global temperatures, associated with anthropogenic climate change, are likely to have marked ecological effects on terrestrial ecosystems. However, the effects of elevated CO2 (eCO2) concentrations on the resurgence of N. lugens that have been treated with pesticides used for transgenic Bt rice cultivation are not fully understood. The present study investigated changes in the protein content, soluble sugar content, free amino acid level, vitellogenin (Nlvg) mRNA expression, and the population growth of N. lugens on transgenic Bt rice (TT51) following triazaophos foliar spray under conditions of eCO2. The results showed that the protein content in the fat bodies and ovaries of N. lugens adult females in TT51 treated with 40 ppm triazophos under eCO2 was significantly higher than under ambient CO2 (aCO2) and was also higher than that in females feeding on the non-transgenic parent (MH63) under aCO2 at different days after emergence (DAEs). The soluble sugar content and free amino level of adult females in TT51 treated with 40 ppm triazophos under eCO2 was significantly higher than under aCO2 and was also higher than in MH63 under aCO2 at 1 and 3 DAE. The Nlvg mRNA expression level of N. lugens adult females in TT51 treated with 40 ppm triazophos under eCO2 was significantly higher than under aCO2 and was also higher than in MH63 under aCO2 at 1 and 3 DAE. The population number of N. lugens in TT51 treated with 40 ppm triazophos under eCO2 was significantly higher than under aCO2 and was also higher than in MH63 under aCO2. The present findings provide important information for integrated pest management with transgenic varieties and a better understanding of the resurgence mechanism of N. lugens under eCO2.

Efficient generation of marker-free transgenic rice plants using an improved transposon-mediated transgene reintegration strategy

Marker-free transgenic plants can be developed through transposon-mediated transgene reintegration, which allows intact transgene insertion with defined boundaries and requires only a few primary transformants. In this study, we improved the selection strategy and validated that the maize (Zea mays) Activator/Dissociation (Ds) transposable element can be routinely used to generate marker-free transgenic plants. A Ds-based gene of interest was linked to green fluorescent protein in transfer DNA (T-DNA), and a green fluorescent protein-aided counterselection against T-DNA was used together with polymerase chain reaction (PCR)-based positive selection for the gene of interest to screen marker-free progeny. To test the efficacy of this strategy, we cloned the Bacillus thuringiensis (Bt) δ-endotoxin gene into the Ds elements and transformed transposon vectors into rice (Oryza sativa) cultivars via Agrobacterium tumefaciens. PCR assays of the transposon empty donor site exhibited transposition in somatic cells in 60.5% to 100% of the rice transformants. Marker-free (T-DNA-free) transgenic rice plants derived from unlinked germinal transposition were obtained from the T1 generation of 26.1% of the primary transformants. Individual marker-free transgenic rice lines were subjected to thermal asymmetric interlaced-PCR to determine Ds(Bt) reintegration positions, reverse transcription-PCR and enzyme-linked immunosorbent assay to detect Bt expression levels, and bioassays to confirm resistance against the striped stem borer Chilo suppressalis. Overall, we efficiently generated marker-free transgenic plants with optimized transgene insertion and expression. The transposon-mediated marker-free platform established in this study can be used in rice and possibly in other important crops.

Development of pod borer-resistant transgenic chickpea using a pod-specific and a constitutive promoter-driven fused cry1Ab/Ac gene

KEY MESSAGE

We studied pod-specific msg promoter from soybean and developed different transgenic lines of chickpea expressing fused cry1Ab/Ac constitutively and pod specifically for resistance against the destructive pest Helicoverpa armigera. Crystal (Cry) proteins derived from the soil bacterium Bacillus thuringiensis (Bt) play an important role in controlling infestation of Helicoverpa armigera, which has been considered a serious problem in chickpea productivity. This study was undertaken to overcome the problem by introducing fused cry1Ab/Ac insecticidal gene under the control of pod-specific soybean msg promoter as well as rice actin1 promoter into chickpea var. DCP 92-3 by Agrobacterium-mediated transformation. Transgenic chickpea lines were characterized by real-time PCR, ELISA and insect bioassay. Expression of fused cry gene under constitutive and pod-specific promoter results in increase of 77- and 110-fold, respectively, compared to non-transgenic control plants. Levels of Cry toxins produced under the control of actin1 and soybean msg promoter were also estimated by ELISA in the leaves and pods, respectively. The higher expression of fused cry gene caused a lethal effect in larvae. The results of insect bioassay study revealed significant reduction in the survival rate of H. armigera reared on transgenic chickpea twigs as well as on pods. Pod-specific promoter-driven fused cry gene provides better and significant management strategy of pest control of chickpea without phenotypic cost.

Cloning and characterization of a multifunctional promoter from maize (Zea mays L.)

The use of tissue-specific promoters to drive the expression of target genes during certain developmental stages or in specific organs can prevent unnecessary gene expression caused by constitutive promoters. Utilizing heterologous promoters to regulate the expression of genes in transgenic receptors can help prevent gene silencing. Here, we engineered heterologous maize promoters that regulate gene-specific expression in rice plant receptors. We performed a histochemical and quantitative β-glucuronidase (GUS) analysis of the Zea mays legumin1 (ZM-LEGF) gene promoter and detailed detection of stably transformed rice expressing the GUS gene under the control of the promoter of ZM-LEGF (pZM-LEGF) and its truncated promoters throughout development. When the promoter sequence was truncated, the location and intensity of GUS expression changed. The results suggest that the sequence from -140 to +41 is a critical region that confers the expression of the entire promoter. Truncation of pZM-LEG (3'-deleted region of pZM-LEGF) markedly increased the GUS activity, with the core cis-elements located in the -273 to -140 regions, namely pZM-LEG6. Detailed analysis of pZM-LEG6::GUS T2 transformant rice seeds and plant tissues at different developmental stages indicated that this promoter is an ideal vegetative tissue-specific promoter that can serve as a valuable tool for transgenic rice breeding and genetic engineering studies.

Bt rice expressing Cry2Aa does not harm Cyrtorhinus lividipennis, a main predator of the nontarget herbivore Nilapavarta lugens

T2A-1 is a newly developed transgenic rice that expresses a synthesized cry2Aa gene driven by the maize ubiquitin promoter. T2A-1 exhibits high resistance against lepidopteran pests of rice. The brown planthopper, Nilapavarta lugens (Stål), is a main nontarget sap-sucking insect pest of rice, and Cyrtorhinus lividipennis (Reuter) is the major predator of the eggs and young nymphs of planthoppers. As C. lividipennis may expose to the Cry2Aa protein via N. lugens, it is therefore essential to assess the potential effects of transgenic cry2Aa rice on this predator. In the present study, three experiments were conducted to evaluate the ecological risk of transgenic cry2Aa rice to C. lividipennis: (1) a direct feeding experiment in which C. lividipennis was fed an artificial diet containing Cry2Aa at the dose of 10-time higher than that it may encounter in the realistic field condition; (2) a tritrophic experiment in which the Cry2Aa protein was delivered to C. lividipennis indirectly through prey eggs or nymphs; (3) a realistic field experiment in which the population dynamics of C. lividipennis were investigated using vacuum-suction. Both direct exposure to elevated doses of the Cry2Aa protein and prey-mediated exposure to realistic doses of the protein did not result in significant detrimental effects on the development, survival, female ratio and body weight of C. lividipennis. No significant differences in population density and population dynamics were observed between C. lividipennis in transgenic cry2Aa and nontransgenic rice fields. It may be concluded that transgenic cry2Aa rice had no detrimental effects on C. lividipennis. This study represents the first report of an assessment continuum for the effects of transgenic cry2Aa rice on C. lividipennis.

Influence of transgenic rice expressing a fused Cry1Ab/1Ac protein on frogs in paddy fields

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.

A 90-day subchronic feeding study of genetically modified rice expressing Cry1Ab protein in Sprague-Dawley rats

Bacillus thuringiensis (Bt) transgenic rice line (mfb-MH86) expressing a synthetic cry1Ab gene can be protected against feeding damage from Lepidopteran insects, including Sesamia inferens, Chilo suppressalis, Tryporyza incertulas and Cnaphalocrocis medinalis. Rice flour from mfb-MH86 and its near-isogenic control MH86 was separately formulated into rodent diets at concentrations of 17.5, 35 and 70 % (w/w) for a 90-day feeding test with rats, and all of the diets were nutritionally balanced. In this study, the responses of rats fed diets containing mfb-MH86 were compared to those of rats fed flour from MH86. Overall health, body weight and food consumption were comparable between groups fed diets containing mfb-MH86 and MH86. Blood samples were collected prior to sacrifice and a few significant differences (p < 0.05) were observed in haematological and biochemical parameters between rats fed genetically modified (GM) and non-GM diets. However, the values of these parameters were within the normal ranges of values for rats of this age and sex, thus not considered treatment related. In addition, upon sacrifice a large number of organs were weighed, macroscopic and histopathological examinations were performed with only minor changes to report. In conclusion, these results demonstrated that no toxic effect was observed in the conditions of the experiment, based on the different parameters assessed. GM rice mfb-MH86 is as safe and nutritious as non-GM rice.

No direct effects of two transgenic Bt rice lines, T1C-19 and T2A-1, on the arthropod communities

A 2-yr field trial was conducted to assess the impacts of two new transgenic Bt rice lines, T1C-19 expressing Cry1C protein and T2A-1 expressing Cry2A protein, on the arthropod community sampled via vacuum. All the arthropods were classified into five guilds, including herbivores, parasitoids, predators, detritivores, and others. The seasonal density and dominance distribution of each guild and community-level indices (species richness, Shannon-Wiener diversity index, Simpson diversity index, and evenness index) were compared among rice types. Principal response curves were used to investigate the differences of entire arthropod community of Bt rice plots relative to non-Bt rice plots. The results showed no significant difference was detected in the community-level indices and dominance distribution of guilds between Bt and non-Bt rice plots. The seasonal density of herbivores, detritivores, and others as well as density of the arthropod overall community were also not significantly affected by rice types in either year, although the density of predators and parasitoids in Bt rice plots was significantly lower than those in non-Bt rice plots. The lower abundances of Braconidae, Eulophidae, Cyrtorhinus lividipennis (Reuter) (Hemiptera: Miridae), and Theridiidae in Bt rice plots are likely attributed to the lower abundances of prey species or hosts. Principal response curves revealed that arthropod community in Bt was similar with that in non-Bt rice plots. In conclusion, our findings indicate that these two tested Bt rice lines had no marked negative effects on the arthropod community in the paddy fields.