Genetically Modified Crops Expressing 35S-Thaumatin II Transgene: Sensory Properties and Food Safety Aspects

Influence of transgenesis on genome variability in cucumber lines with a thaumatin II gene

The development of new plant varieties by genetic modification aims at improving their features or introducing new qualities. However, concerns about the unintended effects of transgenes and negative environmental impact of genetically modified plants are an obstacle for the use of these plants in crops. To analyze the impact of transgenesis on plant genomes, we analyze three cucumber transgenic lines with an introduced thaumatin II gene. After genomes sequencing, we analyzed the transgene insertion site and performed variant prediction. As a result, we obtained similar number of variants for all analyzed lines (average of 4307 polymorphisms), with high abundance in one region of chromosome 4. According to SnpEff analysis, the presence of genomic variants generally does not influence the genome functionality, as less than 2% of polymorphisms have high impact. Moreover, analysis indicates that these changes were more likely induced by in vitro culture than by the transgenesis itself. The insertion site analysis shows that the region of transgene integration could cause changes in gene expression, by gene disruption or loss of promoter region continuity.

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The online version contains supplementary material available at 10.1007/s12298-021-00990-8.

Control of T-DNA Transfer from Agrobacterium tumefaciens to Plants Based on an Inducible Bacterial Toxin-Antitoxin System

High-value pharmaceutical products are already successfully produced in contained facilities using Agrobacterium-mediated transient transformation of plants. However, transfection methods suitable for open field applications are still desirable as a cheaper alternative. Biosafety concerns related to the use of recombinant agrobacteria in an industrial transfection process include possible transformation or transfection of unintended hosts or spread of the genetically modified agrobacteria in the environment. In this paper, we explored a novel biocontrol approach resulting in greater biosafety of the transient expression process in plants. Our proposed solution involves inducible expression of Agrobacterium tumefaciens toxin PemK and antitoxin PemI that provides for strictly regulated T-DNA transfer from agrobacteria to plants. We also identified several other toxins from putative Agrobacterium toxin-antitoxin modules and demonstrate their potential usefulness in the control of Agrobacterium tumefaciens as a DNA vector.

Effect of Transgenesis on mRNA and miRNA Profiles in Cucumber Fruits Expressing Thaumatin II

Transgenic plants are commonly used in breeding programs because of the various features that can be introduced. However, unintended effects caused by genetic transformation are still a topic of concern. This makes research on the nutritional safety of transgenic crop plants extremely interesting. Cucumber (Cucumis sativus L.) is a crop that is grown worldwide. The aim of this study was to identify and characterize differentially expressed genes and regulatory miRNAs in transgenic cucumber fruits that contain the thaumatin II gene, which encodes the sweet-tasting protein thaumatin II, by NGS sequencing. We compared the fruit transcriptomes and miRNomes of three transgenic cucumber lines with wild-type cucumber. In total, we found 47 differentially expressed genes between control and all three transgenic lines. We performed the bioinformatic functional analysis and gene ontology classification. We also identified 12 differentially regulated miRNAs, from which three can influence the two targets (assigned as DEGs) in one of the studied transgenic lines (line 224). We found that the transformation of cucumber with thaumatin II and expression of the transgene had minimal impact on gene expression and epigenetic regulation by miRNA, in the cucumber fruits.

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.

Nucleic acid from beans extracted by ethanediamine magnetic particles

Ethanediamine magnetite nanoparticles (EDAMPs) were used as adsorbents to isolate genomic DNA from various bean-species. A "single-pot" preparation of EDAMPs was described. Further characterization, including transmission electronic microscopy (TEM), scanning electronic microscopy (SEM), thermo-gravimetric analysis (TGA), X-ray powder diffraction (XRD) and Fourier Transform Infrared Spectrophotometer (FT-IR) were used to demonstrate the efficiency of this simple and general identification method. The EDAMPs provided excellent yields of genomic DNA. The isolated DNA was suitable for use in further applications by the Polymerase Chain Reaction (PCR) for the detection of Genetically Modified (GM) food and non-GM food. The EDAMPs are effective for bioseparation applications.