Current perspectives on genetically modified crops and detection methods

Small Interfering RNAs (siRNAs) Negatively Impact Growth and Gene Expression of Environmentally Relevant Bacteria in In Vitro Conditions

Rising global populations have amplified food scarcity and ushered in the development of genetically modified (GM) crops containing small interference RNAs (siRNAs) that control gene expression to overcome these challenges. The use of RNA interference (RNAi) in agriculture remains controversial due to uncertainty regarding the unintended release of genetic material and downstream nontarget effects, which have not been assessed in environmental bacteria to date. To evaluate the impacts of siRNAs used in agriculture on environmental bacteria, this study assessed microbial growth and viability as well as transcription activity with and without the presence of environmental stressors. Results showed a statistically significant reduction in growth capacity and maximum biomass achieved when bacteria are exposed to siRNAs alone and with additional external stress (p < 0.05). Further transcriptomic analysis demonstrated that nutrient cycling gene activities were found to be consistently and significantly altered following siRNA exposure, particularly among carbon (xylA, FBPase, limEH, Chitinase, rgl, rgh, rgaE, mannanase, ara) and nitrogen (ureC, nasA, narB, narG, nirK) cycling genes (p < 0.05). Decreases in carbon cycling gene transcription profiles were generally significantly enhanced when siRNA exposure was coupled with nutrient or antimicrobial stress. Collectively, findings suggest that certain conditions facilitate the uptake of siRNAs from their surrounding environments that can negatively affect bacterial growth and gene expression activity, with uncertain downstream impacts on ecosystem homeostasis.

Genome editing prospects for heat stress tolerance in cereal crops

The world population is steadily growing, exerting increasing pressure to feed in the future, which would need additional production of major crops. Challenges associated with changing and unpredicted climate (such as heat waves) are causing global food security threats. Cereal crops are a staple food for a large portion of the world's population. They are mostly affected by these environmentally generated abiotic stresses. Therefore, it is imperative to develop climate-resilient cultivars to support the sustainable production of main cereal crops (Rice, wheat, and maize). Among these stresses, heat stress causes significant losses to major cereals. These issues can be solved by comprehending the molecular mechanisms of heat stress and creating heat-tolerant varieties. Different breeding and biotechnology techniques in the last decade have been employed to develop heat-stress-tolerant varieties. However, these time-consuming techniques often lack the pace required for varietal improvement in climate change scenarios. Genome editing technologies offer precise alteration in the crop genome for developing stress-resistant cultivars. CRISPR/Cas9 (Clustered regularly interspaced short palindromic repeat/Cas9), one such genome editing platform, recently got scientists' attention due to its easy procedures. It is a powerful tool for functional genomics as well as crop breeding. This review will focus on the molecular mechanism of heat stress and different targets that can be altered using CRISPR/Cas genome editing tools to generate climate-smart cereal crops. Further, heat stress signaling and essential players have been highlighted to provide a comprehensive overview of the topic.

A rapid and high-throughput system for the detection of transgenic products based on LAMP-CRISPR-Cas12a

With the increasing acreage of genetically modified crops worldwide, rapid and efficient detection technologies have become very important for the regulation and screening of GM organisms. We constructed a method based on loop-mediated isothermal amplification (LAMP), CRISPR-Cas12a and lateral flow assay (LAMP-CRISPR-Cas12a-LFA). It is an intuitive, sensitive and specific fluorescence detection and test strip system to detect CP4-EPSPS and Cry1Ab/Ac genes in field screening. The LAMP-CRISPR-Cas12a-LFA method has a limit of detection (LOD) of 100 copies based on lateral flow test strips after optimization of the conditions with screened specific primers, and the entire detection process can be completed within 1 h at 61 °C. The system was used to evaluate field test samples and showed high reproducibility after testing products containing CP4-EPSPS and Cry1Ab/Ac genes, and both were detectable. The LAMP-CRISPR-Cas12a-LFA method established in this paper functions as a rapid field detection method. It requires only one portable thermostatic instrument, which renders it compatible with the rapid detection of field samples and useable at experimental workstations, in law enforcement field work, and in local inspection and quarantine departments.

Genetically engineered crops for sustainably enhanced food production systems

Genetic modification of crops has substantially focused on improving traits for desirable outcomes. It has resulted in the development of crops with enhanced yields, quality, and tolerance to biotic and abiotic stresses. With the advent of introducing favorable traits into crops, biotechnology has created a path for the involvement of genetically modified (GM) crops into sustainable food production systems. Although these plants heralded a new era of crop production, their widespread adoption faces diverse challenges due to concerns about the environment, human health, and moral issues. Mitigating these concerns with scientific investigations is vital. Hence, the purpose of the present review is to discuss the deployment of GM crops and their effects on sustainable food production systems. It provides a comprehensive overview of the cultivation of GM crops and the issues preventing their widespread adoption, with appropriate strategies to overcome them. This review also presents recent tools for genome editing, with a special focus on the CRISPR/Cas9 platform. An outline of the role of crops developed through CRSIPR/Cas9 in achieving sustainable development goals (SDGs) by 2030 is discussed in detail. Some perspectives on the approval of GM crops are also laid out for the new age of sustainability. The advancement in molecular tools through plant genome editing addresses many of the GM crop issues and facilitates their development without incorporating transgenic modifications. It will allow for a higher acceptance rate of GM crops in sustainable agriculture with rapid approval for commercialization. The current genetic modification of crops forecasts to increase productivity and prosperity in sustainable agricultural practices. The right use of GM crops has the potential to offer more benefit than harm, with its ability to alleviate food crises around the world.

CRISPR-Cas systems mediated biosensing and applications in food safety detection

Food safety, closely related to economic development of food industry and public health, has become a global concern and gained increasing attention worldwide. Effective detection technology is of great importance to guarantee food safety. Although several classical detection methods have been developed, they have some limitations in portability, selectivity, and sensitivity. The emerging CRISPR-Cas systems, uniquely integrating target recognition specificity, signal transduction, and efficient signal amplification abilities, possess superior specificity and sensitivity, showing huge potential to address aforementioned challenges and develop next-generation techniques for food safety detection. In this review, we focus on recent progress of CRISPR-Cas mediated biosensing and their applications in food safety monitoring. The properties and principles of commonly used CRISPR-Cas systems are highlighted. Notably, the frequently coupled nucleic acid amplification strategies to enhance their selectivity and sensitivity, especially isothermal amplification methods, as well as various signal output modes are also systematically summarized. Meanwhile, the application of CRISPR-Cas systems-based biosensors in food safety detection including foodborne virus, foodborne bacteria, food fraud, genetically modified organisms (GMOs), toxins, heavy metal ions, antibiotic residues, and pesticide residues is comprehensively described. Furthermore, the current challenges and future prospects in this field are tentatively discussed.

Digital PCR-Based Characterization of a g10evo-epsps Gene-Specific Matrix Reference Material for Its Food and Feed Detection

g10evo-epsps is a novel glyphosate herbicide-resistant gene that has been transferred to various crops such as soybean, corn, cotton, and rice. Here, we developed a gene-specific digital Polymerase Chain Reaction (dPCR) detection method for absolute quantitative analysis of g10evo-epsps, and characterized g10evo-epsps certified reference materials (CRM) using ZUTS-33 soybean powder as the candidate material. Stability tests of matrix CRMs demonstrate that these CRMs can be stored stably for 6 months and transported for 10 days at room temperature and withstand summer high temperatures (below 60 °C). CRM characterization is based on the copy number ratio of g10evo-epsps to lectin. Eight qualified laboratories independently validated the CRM using dPCR method, with a measurement of 0.98 (copy/copy) and an extended uncertainty of 0.08 (copy/copy). The g10evo-epsps matrix CRM described here may be used for qualitative and quantitative testing, method evaluation, laboratory quality control, and other related fields.

Genome Editing: A Promising Approach for Achieving Abiotic Stress Tolerance in Plants

The susceptibility of crop plants towards abiotic stresses is highly threatening to assure global food security as it results in almost 50% annual yield loss. To address this issue, several strategies like plant breeding and genetic engineering have been used by researchers from time to time. However, these approaches are not sufficient to ensure stress resilience due to the complexity associated with the inheritance of abiotic stress adaptive traits. Thus, researchers were prompted to develop novel techniques with high precision that can address the challenges connected to the previous strategies. Genome editing is the latest approach that is in the limelight for improving the stress tolerance of plants. It has revolutionized crop research due to its versatility and precision. The present review is an update on the different genome editing tools used for crop improvement so far and the various challenges associated with them. It also highlights the emerging potential of genome editing for developing abiotic stress-resilient crops.

Genetically Modified Soybean Detection Using a Biosensor Electrode with a Self-Assembled Monolayer of Gold Nanoparticles

In this study, we proposed a genosensor that can qualitatively and quantitatively detect genetically modified soybeans using a simple electrode with evenly distributed single layer gold nanoparticles. The DNA sensing electrode is made by sputtering a gold film on the substrate, and then sequentially depositing 1,6-hexanedithiol and gold nanoparticles with sulfur groups on the substrate. Then, the complementary to the CaMV 35S promoter (P35S) was used as the capture probe. The target DNA directly extracted from the genetically modified soybeans rather than the synthesized DNA segments was used to construct the detection standard curve. The experimental results showed that our genosensor could directly detect genetically modified genes extracted from soybeans. We obtained two percentage calibration curves. The calibration curve corresponding to the lower percentage range (1-6%) exhibits a sensitivity of 2.36 Ω/% with R2 = 0.9983, while the calibration curve corresponding to the higher percentage range (6-40%) possesses a sensitivity of 0.1 Ω/% with R2 = 0.9928. The limit of detection would be 1%. The recovery rates for the 4% and 5.7% GMS DNA were measured to be 104.1% and 102.49% with RSD at 6.24% and 2.54%. The gold nanoparticle sensing electrode developed in this research is suitable for qualitative and quantitative detection of genetically modified soybeans and can be further applied to the detection of other genetically modified crops in the future.

GmoDetector: An accurate and efficient GMO identification approach and its applications

The rapid increase of genetically modified organisms (GMOs) entering the food and feed markets, and the contamination of donor (micro)organisms of transgenic elements make it more challenging for the existing GMO detection. In this study, we developed a high-throughput and contamination-removal GMO detection approach named as GmoDetector. GmoDetector targeted 64 common transgenic elements and 76 GMO-specific events collected from 251 singular GM events, and combined with next generation sequencing (NGS) and target enrichment technology to detect various GMOs. As a result, GmoDetector was able to exclude the donor (micro)organism contamination, and detect the authorized and unauthorized GMOs (UGMOs) in any forms of food or feed, such as processed or unprocessed. The sensitivity of GmoDetector is as low as 0.1% (GMO content), which has met the GMO labeling threshold for all countries. Therefore, GmoDetector is a robust tool for accurate and efficient detection of the authorized and UGMOs.

Nanocarriers-based immobilization of enzymes for industrial application

Nanocarriers-based immobilization strategies are a novel concept in the enhancement of enzyme stability, shelf life and efficiency. A wide range of natural and artificial supports have been assessed for their efficacy in enzyme immobilization. Nanomaterials epitomize unique and fascinating matrices for enzyme immobilization. These structures include carbon nanotubes, superparamagnetic nanoparticles and nanofibers. These nano-based supports offer stable attachment of enzymes, thus ensuring their reusability in diverse industrial applications. This review attempts to encompass recent developments in the critical role played by nanotechnology towards the improvement of the practical applicability of microbial enzymes. Nanoparticles are increasingly being used in combination with various polymers to facilitate enzyme immobilization. These endeavors are proving to be conducive for enzyme-catalyzed industrial operations. In recent years the diversity of nanomaterials has grown tremendously, thus offering endless opportunities in the form of novel combinations for various biotransformation experimentations. These nanocarriers are advantageous for both free enzymes and whole-cell immobilization, thus demonstrating to be relatively effective in several fermentation procedures.

Bioproduction process of natural products and biopharmaceuticals: Biotechnological aspects

Decades of research have been put in place for developing sustainable routes of bioproduction of high commercial value natural products (NPs) on the global market. In the last few years alone, we have witnessed significant advances in the biotechnological production of NPs. The development of new methodologies has resulted in a better understanding of the metabolic flux within the organisms, which have driven manipulations to improve production of the target product. This was further realised due to the recent advances in the omics technologies such as genomics, transcriptomics, proteomics, metabolomics and secretomics, as well as systems and synthetic biology. Additionally, the combined application of novel engineering strategies has made possible avenues for enhancing the yield of these products in an efficient and economical way. Invention of high-throughput technologies such as next generation sequencing (NGS) and toolkits for genome editing Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR-associated 9 (CRISPR/Cas9) have been the game changers and provided unprecedented opportunities to generate rationally designed synthetic circuits which can produce complex molecules. This review covers recent advances in the engineering of various hosts for the production of bioactive NPs and biopharmaceuticals. It also highlights general approaches and strategies to improve their biosynthesis with higher yields in a perspective of plants and microbes (bacteria, yeast and filamentous fungi). Although there are numerous reviews covering this topic on a selected species at a time, our approach herein is to give a comprehensive understanding about state-of-art technologies in different platforms of organisms.

Transposable elements: a jump toward the future of expression vectors

Expression vectors (EVs) are artificial nucleic acid molecules with a modular structure that allows for the transcription of DNA sequences of interest in either cellular or cell-free environments. These vectors have emerged as cross-disciplinary tools with multiple applications in an expanding Life Sciences market. The cis-regulatory sequences (CRSs) that control the transcription in EVs are typically sourced from either viruses or from characterized genes. However, the recent advancement in transposable elements (TEs) technology provides attractive alternatives that may enable a significant improvement in the design of EVs. Commonly known as "jumping genes," due to their ability to move between genetic loci, TEs are constitutive components of both eukaryotic and prokaryotic genomes. TEs harbor native CRSs that allow the regulated transcription of transposition-related genes. However, some TE-related CRSs display striking characteristics, which provides the opportunity to reconsider TEs as lead actors in the design of EVs. In this article, we provide a synopsis of the transcriptional control elements commonly found in EVs together with an extensive discussion of their advantages and limitations. We also highlight the latest findings that may allow for the implementation of TE-derived sequences in the EVs feasible, possibly improving existing vectors. By introducing this new concept of TEs as a source of regulatory sequences, we aim to stimulate a profitable discussion of the potential advantages and benefits of developing a new generation of EVs based on the use of TE-derived control sequences.

A choice experiment on consumer perceptions of three generations of genetically modified foods

Genetically modified (GM) foods remain a contentious issue worldwide, yet consumer preferences in this field have received too little attention in the academic research. The present paper helps fill this gap by investigating the hypothetical consumer behaviour towards and willingness to pay (WTP) for a specific type of GM food (of the first, second or third generation) using a choice experiment with 1444 respondents from three European cities. A random parameter logit-error component (RPL-EC) model allows for heterogeneity in consumer preferences and potential correlation across utilities and across taste parameters. The results show that consumers seem to attach utility to GM foods insofar as they perceive that generational traits improve their nutritional qualities or bring health benefits. Moreover, the role played by education in improving people's understanding of the issues associated with GM foods provides insights to assist marketers in developing differentiated strategies. Marketers would be able to help consumers dampen the effect of fear and allow them to develop more informed opinions, which, however, do not necessarily translate into purchasing behaviour.

Highly sensitive SERS assay of genetically modified organisms in maize via a nanoflower substrate coupled with hybridization chain reaction amplification

A novel biosensor based on a high-density “hot spot” SERS substrate coupled with HCR amplification strategy was developed for the ultrasensitive detection of genetically modified organisms in maize.

DNA walking strategy to identify unauthorized genetically modified bacteria in microbial fermentation products

Recently, unexpected contaminations of unauthorized genetically modified microorganisms (GMM) carrying antimicrobial resistance (AMR) genes were reported in microbial fermentation products commercialized on the food and feed chain. To guarantee the traceability and safety of the food and feed chain, whole-genome sequencing (WGS) has played a key role to prove GMM contaminations via the characterization of unnatural associations of sequences. However, WGS requires a prior microbial isolation of the GMM strain, which can be difficult to successfully achieve. Therefore, in order to avoid such bottleneck, a culture-independent approach was proposed in this study. First, the screening for the aadD gene, an AMR gene conferring a resistance to kanamycin, and for the pUB110 shuttle vector, carrying the aadD gene and commonly used to produce GMM, is performed. In case of a positive signal, DNA walking methods anchored on the two borders of the detected pUB110 shuttle vector are applied to characterize unknown flanking regions. Following to the sequencing of the generated amplicons, unnatural associations of sequences can be identified, allowing to demonstrate the presence of unauthorized GMM. The developed culture-independent strategy was successfully applied on commercialized microbial fermentation products, allowing to prove the presence of GMM contaminations in the food and feed chain.

Structural Aspects of DNA Repair and Recombination in Crop Improvement

The adverse effects of global climate change combined with an exponentially increasing human population have put substantial constraints on agriculture, accelerating efforts towards ensuring food security for a sustainable future. Conventional plant breeding and modern technologies have led to the creation of plants with better traits and higher productivity. Most crop improvement approaches (conventional breeding, genome modification, and gene editing) primarily rely on DNA repair and recombination (DRR). Studying plant DRR can provide insights into designing new strategies or improvising the present techniques for crop improvement. Even though plants have evolved specialized DRR mechanisms compared to other eukaryotes, most of our insights about plant-DRRs remain rooted in studies conducted in animals. DRR mechanisms in plants include direct repair, nucleotide excision repair (NER), base excision repair (BER), mismatch repair (MMR), non-homologous end joining (NHEJ) and homologous recombination (HR). Although each DRR pathway acts on specific DNA damage, there is crosstalk between these. Considering the importance of DRR pathways as a tool in crop improvement, this review focuses on a general description of each DRR pathway, emphasizing on the structural aspects of key DRR proteins. The review highlights the gaps in our understanding and the importance of studying plant DRR in the context of crop improvement.

Nanotechnological interventions for plant health improvement and sustainable agriculture

Agriculture is the source of food for both humans and animals. With the growing population demands, agricultural production needs to be scaled up where nanotechnology can play a significant role. The use of nanotechnology in agriculture can manage plant disease and growth for better and quality output. Therefore, this review focuses on the use of various nanoparticles for detection of nutrients and contaminants, nanosensors for monitoring the environmental stresses and crop conditions as well as the use of nanotechnology for plant pathogen detection and crop protection. In addition, the delivery of plant growth regulators and agrichemicals like nanopesticides and nanofertilizers to the plants along with the delivery of DNA for targeted genetic engineering and production of genetically modified (GM) crops are discussed briefly. Further, the future concerns regarding the use of nanoparticles and their possible toxicity, impact on the agriculture and ecosystem needs to be assessed along with the assessment of the nanoparticles and GM crops on the environment and human health.

Engineering Lactococcus lactis for Increased Vitamin K2 Production

Cheese produced with Lactococcus lactis is the main source of vitamin K2 in the Western diet. Subclinical vitamin K2 deficiency is common, calling for foods with enhanced vitamin K2 content. In this study we describe analyses of vitamin K2 (menaquinone) production in the lactic acid bacterium L. lactis ssp. cremoris strain MG1363. By cloning and expression from strong promoters we have identified genes and bottlenecks in the biosynthetic pathways leading to the long-chained menaquinones, MK-8 and MK-9. Key genes of the biosynthetic menaquinone pathway were overexpressed, singly or combined, to examine how vitamin K2 production can be enhanced. We observed that the production of the long menaquinone polyprenyl side chain, rather than production of the napthoate ring (1,4-dihydroxy-2-naphtoic acid), limits total menaquinone synthesis. Overexpression of genes causing increased ring formation (menF and menA) led to overproduction of short chained MK-3, while overexpression of other key genes (mvk and llmg_0196) resulted in enhanced full-length MK-9 production. Of two putatively annotated prenyl diphosphate synthases we pinpoint llmg_0196 (preA) to be important for menaquinone production in L. lactis. The genes mvk, preA, menF, and menA were found to be important contributors to menaquinone levels as single overexpression of these genes double and more than triple the total menaquinone content in culture. Combined overexpression of mvk, preA, and menA increased menaquinone levels to a higher level than obtained individually. When the overproducing strains were applied for milk fermentations vitamin K2 content was effectively increased 3-fold compared to the wild type. The results provide a foundation for development of strains to ferment foods with increased functional value i.e., higher vitamin K2 content.

An Interdisciplinary Approach to Study the Performance of Second-generation Genetically Modified Crops in Field Trials: A Case Study With Soybean and Wheat Carrying the Sunflower HaHB4 Transcription Factor

Research, production, and use of genetically modified (GM) crops have split the world between supporters and opponents. Up to now, this technology has been limited to the control of weeds and pests, whereas the second generation of GM crops is expected to assist farmers in abiotic stress tolerance or improved nutritional features. Aiming to analyze this subject holistically, in this presentation we address an advanced technology for drought-tolerant GM crops, upscaling from molecular details obtained in the laboratory to an extensive network of field trials as well as the impact of the introduction of this innovation into the market. Sunflower has divergent transcription factors, which could be key actors in the drought response orchestrating several signal transduction pathways, generating an improved performance to deal with water deficit. One of such factors, HaHB4, belongs to the homeodomain-leucine zipper family and was first introduced in Arabidopsis. Transformed plants had improved tolerance to water deficits, through the inhibition of ethylene sensitivity and not by stomata closure. Wheat and soybean plants expressing the HaHB4 gene were obtained and cropped across a wide range of growing conditions exhibiting enhanced adaptation to drought-prone environments, the most important constraint affecting crop yield worldwide. The performance of wheat and soybean, however, differed slightly across mentioned environments; whereas the improved behavior of GM wheat respect to controls was less dependent on the temperature regime (cool or warm), differences between GM and wild-type soybeans were remarkably larger in warmer compared to cooler conditions. In both species, these GM crops are good candidates to become market products in the near future. In anticipation of consumers' and other stakeholders' interest, spectral analyses of field crops have been conducted to differentiate these GM crops from wild type and commercial cultivars. In this paper, the potential impact of the release of such market products is discussed, considering the perspectives of different stakeholders.

Development of a sensitive monoclonal antibody-based sandwich ELISA to detect Vip3Aa in genetically modified crops

Objectives

To develop a sensitive monoclonal antibody-based sandwich enzyme-linked immunosorbent assay (ELISA) to detect Vip3Aa in genetically modified (GM) crops and their products.

Results

Vegetative insecticidal proteins (Vips) are secreted by Bacillus thuringiensis (Bt) and are known to be toxic to Lepidoptera species. Vip3Aa family proteins, Vip3Aa19 and Vip3Aa20, were successfully applied in GM crops to confer an effective and persistent insecticidal resistance. A sensitive monoclonal antibody-based sandwich ELISA was developed to detect Vip3Aa in GM crops and their products. Two monoclonal antibodies were raised against the overexpressed and purified His-Vip3Aa20, were purified from mouse ascites and characterized. A sandwich ELISA method was developed using the 2G3-1D7 monoclonal antibody for capture and the biotin-labeled 1F9-1F5 monoclonal antibody for detection of Vip3Aa20. The linear detection range of the method was found to be approximately 31.25–500 pg/ml, with a sensitivity of 10.24 pg/ml.

Conclusions

The established ELISA was effective for detecting Vip3Aa family proteins other than Vip3Aa8, and was successfully applied in the detection of Vip3Aa20 and Vip3Aa19 expressed in transgenic maize and cotton.

Transgenic crops for the agricultural improvement in Pakistan: a perspective of environmental stresses and the current status of genetically modified crops

Transgenic technologies have emerged as a powerful tool for crop improvement in terms of yield, quality, and quantity in many countries of the world. However, concerns also exist about the possible risks involved in transgenic crop cultivation. In this review, literature is analyzed to gauge the real intensity of the issues caused by environmental stresses in Pakistan. In addition, the research work on genetically modified organisms (GMOs) development and their performance is analyzed to serve as a guide for the scientists to help them select useful genes for crop transformation in Pakistan. The funding of GMOs research in Pakistan shows that it does not follow the global trend. We also present socio-economic impact of GM crops and political dimensions in the seed sector and the policies of the government. We envisage that this review provides guidelines for public and private sectors as well as the policy makers in Pakistan and in other countries that face similar environmental threats posed by the changing climate.

Comparative Proteomics of Phytase-transgenic Maize Seeds Indicates Environmental Influence is More Important than that of Gene Insertion

Proteomic differences were compared between phytase-transgenic (PT) maize seeds and nontransgenic (NT) maize seeds through two-dimensional electrophoresis (2-DE) with mass spectrometry (MS). When maize was grown under field conditions, 30 differentially accumulated proteins (DAPs) were successfully identified in PT seeds (PT/NT). Clusters of Orthologous Groups (COG) functional classification of these proteins showed that the largest group was associated with posttranslational modifications. To investigate the effects of environmental factors, we further compared the seed protein profiles of the same maize planted in a greenhouse or under field conditions. There were 76 DAPs between the greenhouse- and field-grown NT maize seeds and 77 DAPs between the greenhouse- and field-grown PT maize seeds However, under the same planting conditions, there were only 43 DAPs (planted in the greenhouse) or 37 DAPs (planted in the field) between PT and NT maize seeds. The results revealed that DAPs caused by environmental factors were more common than those caused by the insertion of exogenous genes, indicating that the environment has much more important effects on the seed protein profiles. Our maize seed proteomics results also indicated that the occurrence of unintended effects is not specific to genetically modified crops (GMCs); instead, such effects often occur in traditionally bred plants. Our data may be beneficial for biosafety assessments of GMCs at the protein profile level in the future.

Production of Marker-Free Apple Plants Expressing the Supersweet Protein Gene Driven by Plant Promoter

The presence of antibiotic resistance and other marker genes in genetically modified plants causes concern in society because of perceived risks for the environment and human health. The creation of transgenic plants that do not contain foreign genetic material, especially that of bacterial and viral origin, largely alleviates the tension and makes the plants potentially more attractive for consumers. To produce marker-free transgenic apple plants, we used the pMF1 vector, which combines Zygosaccharomyces rouxii recombinaseR and a CodA-nptII bifunctional selectable gene. The thaumatin II gene from the tropical plant Thaumatococcus daniellii, which is under the control of the plant E8 gene (a predominantly fruit-specific promoter) and rbsS3A terminator, was taken as the gene of interest for modification of the fruit taste and enhancing its sweetness. Exploitation of this gene in our laboratory has allowed enhancing the sweetness, as well as improving the taste characteristics, of fruits and vegetables of plants such as strawberry, carrot, tomato and pear. We have obtained three independent transgenic apple lines that have been analyzed by PCR and Southern blot analyses for the presence of T-DNA sequences. Two of them contained a partial sequence of the T-DNA. With one line containing the full insert we then used a delayed strategy for the selection of marker-free plants. After induction of recombinase activity in leaf explants on selective media with 5-fluorocytosine (5-FC) we obtained more than 30 sublines, most of which lost their resistance to kanamycin. Most of the apple sublines showed the expression of the supersweet protein gene in a wide range of levels as detected by RNA accumulation. The plants from the group with the highest transcript level were propagated and grafted onto dwarf rootstocks for early fruit production for future estimates of protein levels and organoleptic analyses. Thus, we developed a protocol that allowed the production of marker-free apple plants expressing the supersweet protein.

Detection of Transgenic Proteins by Immunoassays

Rapid development and global cultivation of genetically modified (GM) crops necessitated the use of analytical tools that detect GM crops throughout the product life cycle. Antibody-based immunoassays such as enzyme-linked immunosorbent assays (ELISA) are instrumental in detecting protein expression in transgenic plants. These analytical tools are used throughout development, regulatory registration, commercialization, and stewardship of biotech products. Here we describe the Cry1F ELISA analytical method protocol, data generation and review, and troubleshooting of technical challenges.