Green-tissue-specific, C(4)-PEPC-promoter-driven expression of Cry1Ab makes transgenic potato plants resistant to tuber moth (Phthorimaea operculella, Zeller)

Genome-Wide Tissue-Specific Genes Identification for Novel Tissue-Specific Promoters Discovery in Soybean

Promoters play a crucial role in controlling the spatial and temporal expression of genes at transcriptional levels in the process of higher plant growth and development. The spatial, efficient, and correct regulation of exogenous genes expression, as desired, is the key point in plant genetic engineering research. Constitutive promoters widely used in plant genetic transformation are limited because, sometimes, they may cause potential negative effects. This issue can be solved, to a certain extent, by using tissue-specific promoters. Compared with constitutive promoters, a few tissue-specific promoters have been isolated and applied. In this study, based on the transcriptome data, a total of 288 tissue-specific genes were collected, expressed in seven tissues, including the leaves, stems, flowers, pods, seeds, roots, and nodules of soybean (Glycine max). KEGG pathway enrichment analysis was carried out, and 52 metabolites were annotated. A total of 12 tissue-specific genes were selected via the transcription expression level and validated through real-time quantitative PCR, of which 10 genes showed tissue-specific expression. The 3-kb 5' upstream regions of ten genes were obtained as putative promoters. Further analysis showed that all the 10 promoters contained many tissue-specific cis-elements. These results demonstrate that high-throughput transcriptional data can be used as effective tools, providing a guide for high-throughput novel tissue-specific promoter discovery.

The root-specific NtR12 promoter-based expression of RIP increased the resistance against bacterial wilt disease in tobacco

BACKGROUND

Tobacco is an important economic crop, but the quality and yield have been severely impaired by bacterial wilt disease (BWD) caused by Ralstonia solanacearum.

METHODS AND RESULTS

Here, we describe a transgenic approach to prevent BWD in tobacco plants. A new root-specific promoter of an NtR12 gene was successfully cloned. The NtR12 promoter drove GUS reporter gene expression to a high level in roots but to less extent in stems, and no significant expression was detected in leaves. The Ribosome-inactivating proteins (RIP) gene from Momordica charantia was also cloned, and its ability to inhibit Ralstonia solanacearum was evaluated using RIP protein produced by the prokaryotic expression system. The RIP gene was constructed downstream of the NtR12 promoter and transformed into the tobacco cultivar "Cuibi No. 1" (CB-1), resulting in many descendants. The resistance against BWD was significantly improved in transgenic tobacco lines expressing NtR12::RIP.

CONCLUSION

This study confirms that the RIP gene confers resistance to BWD and the NtR12 as a new promoter for its specific expression in root and stem. Our findings pave a novel avenue for transgenic engineering to prevent the harmful impact of diseases and pests in roots and stems.

Immune analysis of cry1Ab-genetically modified potato by in-silico analysis and animal mode

The safety of feeding transgenic potato (Solanum tuberosum), resistant to the potato tuber moth, to Wistar rats was examined from an immunological perspective. The genetically modified potato (GMP) was harbouring cry1Ab and nptII genes as target and selectable marker genes, respectively. In-silico analysis reconfirmed that Cry1Ab and NPTII protein sequences have no significant homology to known toxins or known allergens. The Wistar rats were fed a diet containing 20% GMP or its parental control, non-GMP (NGMP), for 90 days. The consumption of GMP food did not affect the growth rate, food intake, food efficiency, and general health status of the rats. There were no significant differences in the serum concentrations of immunoglobulin A (IgA), IgG, IgM, interleukin 6 (IL-6), and IFN-γ between GMP and NGMP-fed rats. Based on such data, it is concluded that the transgenic potato had no adverse effect on immunity functions of Wistar rats.

Isolation and Characterization of a Green-Tissue Promoter from Common Wild Rice (Oryza rufipogon Griff.)

Promoters play a very important role in the initiation and regulation of gene transcription. Green-tissue promoter is of great significance to the development of genetically modified crops. Based on RNA-seq data and RT-PCR expression analysis, this study screened a gene, OrGSE (GREEN SPECIAL EXPRESS), which is expressed specifically in green tissues. The study also isolated the promoter of the OrGSE gene (OrGSEp), and predicted many cis-acting elements, such as the CAAT-Box and TATA-Box, and light-responding elements, including circadian, G-BOX and GT1 CONSENSUS. Histochemical analysis and quantification of GUS activity in transgenic Arabidopsis thaliana plants expressing GUS under the control of OrGSEp revealed that this promoter is not only green tissue-specific, but also light-inducible. The ability of a series of 5’-deletion fragments of OrGSEp to drive GUS expression in Arabidopsis was also evaluated. We found that the promoter region from −54 to −114 is critical for the promoter function, and the region from −374 to −114 may contain core cis-elements involved in light response. In transgenic rice expressing GUS under the control of OrGSEp, visualization and quantification of GUS activity showed that GUS was preferentially expressed in green tissues and not in endosperm. OrGSEp is a useful regulatory element for breeding pest-resistant crops.

Isolation of five rice nonendosperm tissue-expressed promoters and evaluation of their activities in transgenic rice

Using promoters expressed in nonendosperm tissues to activate target genes in specific plant tissues or organs with very limited expression in the endosperm is an attractive approach in crop transgenic engineering. In this article, five putative nonendosperm tissue-expressed promoters were cloned from the rice genome and designated P_OsNETE1 , P_OsNETE2 , P_OsNETE3 , P_OsNETE4 and P_OsNETE5 . By qualitatively and quantitatively examining GUSplus reporter gene expression in transgenic rice plants, P_OsNETE1 -P_OsNETE5 were all found to be active in the roots, leaves, stems, sheaths and panicles but not in the endosperm of plants at different developmental stages. In addition, P_OsNETE2 , P_OsNETE4 and P_OsNETE5 were also inactive in rice embryos. Among these promoters, P_OsNETE4 and P_OsNETE5 exhibited higher activities in all of the tested tissues, and their activities in stems, leaves, roots and sheaths were higher than or comparable to those of the rice Actin1 promoter. We also progressively monitored the activities of P_OsNETE1 -P_OsNETE5 in two generations of single-copy lines and found that these promoters were stably expressed between generations. Transgenic rice was produced using P_OsNETE4 and P_OsNETE5 to drive a modified Bt gene, mCry1Ab. Bt protein expressed in the tested plants ranged from 1769.4 to 4428.8 ng/g fresh leaves, whereas Bt protein was barely detected in the endosperm. Overall, our study identified five novel nonendosperm tissue-expressed promoters that might be suitable for rice genetic engineering and might reduce potential social concern regarding the safety of GMO crops.

Comparative compositional analysis of transgenic potato resistant to potato tuber moth (PTM) and its non-transformed counterpart

In this study, the compositions of transgenic potatoes (TPs) resistant to potato tuber moth (Phthorimaea operculella) were compared with those of its non-transgenic (NTP) counterparts. The light inducible promoter, phosphoenolpyruvate carboxylase led to the expression of Cry1Ab only in the leaves and light-treated tubers of the TPs. No significant differences were found in the moisture, ash, dry weight, total soluble protein, carbohydrate, starch, fiber, ascorbate, cations, anions, fatty acids, and glycoalkaloids contents of TP and NTP. Moreover, light treatment significantly affected the contents of ascorbate, acetate and nitrite anions, palmitic, stearic and linolenic fatty acids, α-haconine and α-solanine glycoalkaloids in TP and NTP tubers. While, significant differences were observed in the amino acid contents in light-treated tubers of TPs than the NTP ones. Although, light treatment in potato tubers resulted in marked metabolic changes, all the variations observed in the metabolites compositions were found to be within the desired reference ranges for potato plants. In conclusion, the results indicated that the TPs were substantially and nutritionally equivalent to the NTP counterparts.

Principales promotores utilizados en la transformación genética de plantas

El conocimiento pleno de los promotores determina el éxito en la obtención de nuevos cultivares de plantas a través de técnicas biotecnológicas, ya que dicha secuencia del ADN regula la transcripción de otras regiones adyacentes o cercanas, encontrándose los siguientes promotores: constitutivos, tejido-específicos o estadio-específicos, inducibles y sintéticos. En esta revisión se resume de manera precisa los conceptos, ventajas y limitaciones de los distintos tipos de promotores, con ejemplos claros de ello.Palabras clave: promotor, biotecnología vegetal, transcripción genética.

Green tissue-specific co-expression of chitinase and oxalate oxidase 4 genes in rice for enhanced resistance against sheath blight

Green tissue-specific simultaneous overexpression of two defense-related genes ( OsCHI11 & OsOXO4 ) in rice leads to significant resistance against sheath blight pathogen ( R. solani ) without distressing any agronomically important traits. Overexpressing two defense-related genes (OsOXO4 and OsCHI11) cloned from rice is effective at enhancing resistance against sheath blight caused by Rhizoctonia solani. These genes were expressed under the control of two different green tissue-specific promoters, viz. maize phosphoenolpyruvate carboxylase gene promoter, PEPC, and rice cis-acting 544-bp DNA element, immediately upstream of the D54O translational start site, P D54O-544 . Putative T0 transgenic rice plants were screened by PCR and integration of genes was confirmed by Southern hybridization of progeny (T1) rice plants. Successful expression of OsOXO4 and OsCHI11 in all tested plants was confirmed. Expression of PR genes increased significantly following pathogen infection in overexpressing transgenic plants. Following infection, transgenic plants exhibited elevated hydrogen peroxide levels, significant changes in activity of ROS scavenging enzymes and reduced membrane damage when compared to their wild-type counterpart. In a Rhizoctonia solani toxin assay, a detached leaf inoculation test and an in vivo plant bioassay, transgenic plants showed a significant reduction in disease symptoms in comparison to non-transgenic control plants. This is the first report of overexpression of two different PR genes driven by two green tissue-specific promoters providing enhanced sheath blight resistance in transgenic rice.

Production of marker-free transgenic rice expressing tissue-specific Bt gene

The hybrid Bacillus thuringiensis (Bt) δ-endotoxin gene Cry1Ab/Ac was used to develop a transgenic Bt rice (Oryza sativa L.) targeting lepidopteran insects of rice. Here, we show the production of a marker-free and tissue-specific expressing transgenic Bt rice line L24 using Agrobacterium-mediated transformation and a chemically regulated, Cre/loxP-mediated DNA recombination system. L24 carries a single copy of marker-free T-DNA that contains the Cry1Ab/Ac gene driven by a maize phosphoenolpyruvate carboxylase (PEPC) gene promoter. The marker-free T-DNA was integrated into the 3' untranslated region of rice gene Os01g0154500 on the short arm of chromosome 1. Compared to the constitutive and non-specific expression of the P (Actin1):Cry1Ab/Ac:T (Nos) gene in the control Bt rice line T51-1, the P ( Pepc ):Cry1Ab/Ac:T (Nos ) gene was detected only in the leaf and stem tissues of L24. More importantly, compared to high levels of CRY1Ab/Ac proteins accumulated in T51-1 seeds, the CRY1Ab/Ac proteins were not detectable in L24 seeds by Western blot analysis. As demonstrated by insect bioassay, L24 provided similar level of resistance to rice leaffolder (Cnaphalocrocis medinalis) as T51-1. The marker-free transgenic line L24 can be used directly in rice breeding for insect resistance to lepidopteran insects where absence of Bt toxin protein in the seed is highly desirable.