Transformation of a marker-free and vector-free antisense ACC oxidase gene cassette into melon via the pollen-tube pathway

Evaluation of antibacterial properties of nisin peptide expressed in carrots

Nisin, derived from Lactococcus lactis, is a well-known natural food preservative. In the present study, the gene of nisin was transformed to carrot by Agrobacterium tumefaciens strain LBA4404 harboring the recombinant binary vector pBI121 containing neomycin phosphotransferase II (nptII) gene, peptide signal KDEL, and Kozak sequence. The integration of nisin and nptII transgenes into the plant genome was confirmed by polymerase chain reaction (PCR) and dot blot analysis. The gene expression was also performed by RT-PCR and Enzyme-Linked Immunosorbent Assay. The level of nisin expressed in one gram of transgenic plant ranged from 0.05 to 0.08 μg/ml. The stability of nisin varied in orange and peach juices depending on the temperature on the 70th day. The leaf protein extracted from the transgenic plant showed a significant preservative effect of nisin in peach and orange juice. A complete inhibition activity against Staphylococcus aureus and Escherichia coli in orange juice was observed within 24 h. After 24 h, log 1 and log 2 were obtained in a peach juice containing Staphylococcus aureus and Escherichia coli, respectively. Results of HPLC indicated that Chlorogenic and Chicoric acid compounds were increased in transgenic plants, but this increase was not significant. The study of determining the genetic stability of transgenic plants in comparison with non-transgenic plants showed high genetic stability between non-transgenic plants and transgenic plants. This study confirmed the significant inhibitory effect of nisin protein on gram-positive and gram-negative bacteria.

Myths and Realities about Genetically Modified Food: A Risk-Benefit Analysis

The development and consumption of genetically modified (GM) crops are surrounded by controversy. According to proponents, only molecular biology approaches and genetic engineering tools are realistic food shortage solutions for the world’s ever-growing population. The main purpose of this study is to review the impact of GM products on human, animal, and environmental health. People still reject GM crops not only because of safety concerns, but also for moral reasons. Toxicity, allergies, and possible horizontal gene transfer (HGT) to the environment or to other species have been associated with the marketing of GM products. Moreover, the scarce data available about the long-term implications of using GM crops is another opponent concern. Nevertheless, science has evidenced no harm from GM crops use to date but has, instead, reported several benefits that result from their commercialization, such as economic, environmental, and health benefits for the general public. Legislation and policies about GM product labeling standards are being discussed. To overcome emerging food security challenges, considering quality scientific information is essential rather than leaving the issue and merely moving toward moral discussion. Hence, a risk–benefit analysis is necessary.

ptxD/Phi as alternative selectable marker system for genetic transformation for bio-safety concerns: a review

Antibiotic and herbicide resistance genes are the most common marker genes for plant transformation to improve crop yield and food quality. However, there is public concern about the use of resistance marker genes in food crops due to the risk of potential gene flow from transgenic plants to compatible weedy relatives, leading to the possible development of “superweeds” and antibiotic resistance. Several selectable marker genes such as aph, nptII, aaC3, aadA, pat, bar, epsp and gat, which have been synthesized to generate transgenic plants by genetic transformation, have shown some limitations. These marker genes, which confer antibiotic or herbicide resistance and are introduced into crops along with economically valuable genes, have three main problems: selective agents have negative effects on plant cell proliferation and differentiation, uncertainty about the environmental effects of many selectable marker genes, and difficulty in performing recurrent transformations with the same selectable marker to pyramid desired genes. Recently, a simple, novel, and affordable method was presented for plant cells to convert non-metabolizable phosphite (Phi) to an important phosphate (Pi) for developing cells by gene expression encoding a phosphite oxidoreductase (PTXD) enzyme. The ptxD gene, in combination with a selection medium containing Phi as the sole phosphorus (P) source, can serve as an effective and efficient system for selecting transformed cells. The selection system adds nutrients to transgenic plants without potential risks to the environment. The ptxD/Phi system has been shown to be a promising transgenic selection system with several advantages in cost and safety compared to other antibiotic-based selection systems. In this review, we have summarized the development of selection markers for genetic transformation and the potential use of the ptxD/Phi scheme as an alternative selection marker system to minimize the future use of antibiotic and herbicide marker genes.

Genome-wide identification of microRNAs involved in the regulation of fruit ripening and climacteric stages in melon (Cucumis melo)

Fruit ripening is influenced by multiple plant hormones and the regulation of genes. However, studies on posttranscriptional regulators (e.g., miRNAs) of fruit growth and ripening are limited. We used miRNA sequencing and degradome methods to identify miRNAs and their target genes in melon (Cucumis melo cv. Hetao melon). A total of 61 conserved miRNAs and 36 novel miRNAs were identified from fruit growth, ripening, climacteric, and postclimacteric developmental stage samples, of which 32 conserved miRNAs were differentially expressed between developmental stage samples. Sixty-two target genes of 43 conserved miRNAs and 1 novel miRNA were identified from degradome sequencing. To further investigate miRNA influencing fruit ripening, transgenic melon plants overexpressing pre-cme-miR393 (cme-miR393-OE) were generated and characterized. The results showed that fruit ripening was delayed in cme-miR393-OE transgenic lines compared to nontransgenic fruits. The target of cme-miR393 was also identified, and the expression of CmAFB2 was repressed in transgenic plants. These results provide evidence that miRNA regulates melon fruit ripening and provide potential targets to improve the horticultural traits of melon fruit.

Genome-wide identification and characterization of long non-coding RNAs involved in fruit ripening and the climacteric in Cucumis melo

BACKGROUND

Cucumis melo is a suitable study material for investigation of fruit ripening owing to its climacteric nature. Long non-coding RNAs have been linked to many important biological processes, such as fruit ripening, flowering time regulation, and abiotic stress responses in plants. However, knowledge of the regulatory roles of lncRNAs underlying the ripening process in C. melo are largely unknown. In this study the complete transcriptome of Cucumis melo L. cv. Hetao fruit at four developmental stages was sequenced and analyzed. The potential role of lncRNAs was predicted based on the function of differentially expressed target genes and correlated genes.

RESULTS

In total, 3857 lncRNAs were assembled and annotated, of which 1601 were differentially expressed between developmental stages. The target genes of these lncRNAs and the regulatory relationship (cis- or trans-acting) were predicted. The target genes were enriched with GO terms for biological process, such as response to auxin stimulus and hormone biosynthetic process. Enriched KEGG pathways included plant hormone signal transduction and carotenoid biosynthesis. Co-expression network construction showed that LNC_002345 and LNC_000154, which were highly expressed, might co-regulate with mutiple genes associated with auxin signal transduction and acted in the same pathways. We identified lncRNAs (LNC_000987, LNC_000693, LNC_001323, LNC_003610, LNC_001263 and LNC_003380) that were correlated with fruit ripening and the climacteric, and may participate in the regulation of ethylene biosynthesis and metabolism and the ABA signaling pathway. A number of crucial transcription factors, such as ERFs, WRKY70, NAC56, and NAC72, may also play important roles in the regulation of fruit ripening in C. melo.

CONCLUSIONS

Our results predict the regulatory functions of the lncRNAs during melon fruit development and ripening, and 142 highly expressed lncRNAs (average FPKM > 100) were identified. These lncRNAs participate in the regulation of auxin signal transduction, ethylene, sucrose biosynthesis and metabolism, the ABA signaling pathway, and transcription factors, thus regulating fruit development and ripening.

Pollen Tube Pathway-Mediated Cotton Transformation

Although many gene transfer methods have been employed for successfully obtaining transgenic cotton, the major constraint in cotton improvement is the limitation of genotype because the majority of transgenic methods require plant regeneration from a single transformed cell which is limited by cotton tissue culture. Comparing with other plant species, it is difficult to induce plant regeneration from cotton; currently, only a limited number of cotton cultivars can be cultured for obtaining regenerated plants. Thus, developing a simple and genotype-independent genetic transformation method is particularly interested for cotton. In this chapter, we present a simple, cost-efficient, and genotype-independent cotton transformation method - pollen tube pathway-mediated transformation. This method uses pollen tube pathway to deliver transgene into cotton embryo sacs and then insert foreign genes into cotton genome. There are three major steps for pollen tube pathway-mediated genetic transformation, which include injection of foreign genes into pollen tube, integration of foreign genes into plant genome, and selection of transgenic plants.

Transgenic Cotton: From Biotransformation Methods to Agricultural Application

Transgenic cotton is among the first transgenic plants commercially adopted around the world. Since it was first introduced into the field in the middle of the 1990s, transgenic cotton has been quickly adopted by cotton farmers in many developed and developing countries. Transgenic cotton has offered many important environmental, social, and economic benefits, including reduced usage of pesticides, indirect increase of yield, minimizing environmental pollution, and reducing labor and cost. Agrobacterium-mediated genetic transformation method is the major method for obtaining transgenic cotton. However, pollen tube pathway-mediated method is also used, particularly by scientists in China, to breed commercial transgenic cotton. Although transgenic cotton plants with disease resistance, abiotic stress tolerance, and improved fiber quality have been developed in the past decades, insect-resistant and herbicide-tolerant cottons are the two dominant cottons in transgenic cotton market.

Cotton transformation via pollen tube pathway

Although many gene transfer methods have been employed for successfully obtaining transgenic cotton, the major constraint in cotton improvement is the limitation of genotype because the majority of transgenic methods require plant regeneration from a single transformed cell which is limited by cotton tissue culture. Comparing with other plant species, it is difficult to induce plant regeneration from cotton; currently, only a limited number of cotton cultivars can be cultured for obtaining regenerated plants. Thus, development of a simple and genotype-independent genetic transformation method is particularly important for cotton community. In this chapter, we present a simple, cost-efficient, and genotype-independent cotton transformation method-pollen tube pathway-mediated transformation. This method uses pollen tube pathway to deliver transgene into cotton embryo sacs and then insert foreign genes into cotton genome. There are three major steps for pollen tube pathway-mediated genetic transformation, which include injection of -foreign genes into pollen tube, integration of foreign genes into plant genome, and selection of transgenic plants.

Transgenic cotton: from biotransformation methods to agricultural application

Transgenic cotton is among the first transgenic plants commercially adopted around the world. Since it was first introduced into the field in the middle of 1990s, transgenic cotton has been quickly adopted by cotton farmers in many developed and developing countries. Transgenic cotton has offered many important environmental, social, and economic benefits, including reduced usage of pesticides, indirect increase of yield, minimizing environmental pollution, and reducing labor and cost. Agrobacterium-mediated genetic transformation method is the major method for obtaining transgenic cotton. However, pollen tube pathway-mediated method is also used, particularly by scientists in China, to breed commercial transgenic cotton. Although transgenic cotton plants with disease-resistance, abiotic stress tolerance, and improved fiber quality have been developed in the past decades, insect-resistant and herbicide-tolerant cotton are the two dominant transgenic cottons in the transgenic cotton market.

Histological study of organogenesis in Cucumis melo L. after genetic transformation: why is it difficult to obtain transgenic plants?

Melon (Cucumis melo L.) is widely considered as a recalcitrant species for genetic transformation. In this study, we developed different regeneration and transformation protocols and we examined the regeneration process at different steps by histological studies. The highest regeneration rate (1.13 ± 0.02 plants per explant) was obtained using cotyledon explants of the 'Védrantais' genotype on Murashige and Skoog (MS) medium supplemented with 0.2 mg/l 6-benzylaminopurine (BAP) and 0.2 mg/l dimethylallylaminopurine (2-iP). Agrobacterium tumefaciens-mediated transformations with the uidA reporter gene were realized on cotyledon explants cultivated in these conditions: 70-90% of explants expressed a transient GUS activity during the early stages of regeneration, however, only few transgenic plants were obtained (1.8-4.5% of stable transformation with the GV2260pBI101 strain). These results revealed a low capacity of melon GUS-positive cells to regenerate transgenic plants. To evaluate the influence of the Agrobacterium infection on plant regeneration, histological analyses were conducted on explants 2, 7, 15, and 28 days after co-culture with the GV2260pBI101 strain. Genetic transformation occurred in epidermal and sub-epidermal cells and reached the meristematic structures expressing a high level of GUS activity during 14 days of culture; but after this period, most of the meristematic structures showed premature cell vacuolization and disorganization. This disruption of the GUS-positive meristematic areas could be responsible of the difficulties encountered to regenerate melon plants after genetic transformation.