Generation of insect-resistant and glyphosate-tolerant rice by introduction of a T-DNA containing two Bt insecticidal genes and an EPSPS gene

Enhances the resistance of rice to lepidopteran pests by fusing the Cry1Ca and Cry2Aa genes with self-cleavage peptide sequence

BACKGROUND

Accumulation of two or more Bacillus thuringiensis (Bt) proteins in plant not only improves the resistance to pests and broadens the resistance spectrum of crops, but also delays the development of pest resistance.

RESULTS

The self-cleavage peptide sequence was used to link two codon-optimized genes, so as to achieve simultaneous accumulation of two low homologous insecticidal proteins in one plant. The rice transformants accumulating Cry1Ca and Cry2Aa proteins were fed to local lepidopteran pests and the larva mortality in 5 days were 100%. The sum of Cry1Ca and Cry2Aa proteins in leaves of transformants E1C&2A-1 and E2A&1C-18 were 10.60 and 9.55 μg g-1 fresh weight (FW), respectively, and the larva mortality of fall armyworm fed on their leaves for 5 days reached 100%. For the control transformants that expressed one Bt protein, the content of Cry1Ca in leaves of transformant E1CM031 was 14.94 μg g-1 FW, and that of Cry2Aa in leaves of transformant B2A4008S was 11.90 μg g-1 FW, but the larva mortality of fall armyworm fed on leaves of E1CM031 and B2A4008S for 5 days were 77.78% and 52.78%, respectively. Although the total Bt contents in transformants expressing one Bt protein were higher than that of transformants expressing two Bt proteins, the lethality of transformants expressing one Bt protein were obviously lower than that of transformants expressing two Bt proteins.

CONCLUSION

The lethal effect of accumulating both Cry1Ca and Cry2Aa proteins in rice was stronger than that of amassing Cry1Ca or Cry2Aa protein only, which meant there was synergistic effect between Cry1Ca and Cry2Aa proteins. © 2024 Society of Chemical Industry.

Stacking Multiple Genes Improves Resistance to Chilo suppressalis, Magnaporthe oryzae, and Nilaparvata lugens in Transgenic Rice

The ability of various pests and diseases to adapt to a single plant resistance gene over time leads to loss of resistance in transgenic rice. Therefore, introduction of different pest and disease resistance genes is critical for successful cultivation of transgenic rice strains with broad-spectrum resistance to multiple pathogens. Here, we produced resistance rice lines with multiple, stacked resistance genes by stacking breeding and comprehensively evaluated their resistance to Chilo suppressalis (striped rice stemborer), Magnaporthe oryzae (rice blast), and Nilaparvata lugens (brown planthopper) in a pesticide-free environment. CRY1C and CRY2A are exogenous genes from Bacillus thuringiensis. Pib, Pikm, and Bph29 are natural genes in rice. CH121TJH was introduced into CRY 1C, Pib, Pikm, and Bph29. CH891TJH and R205XTJH were introduced into CRY 2A, Pib, Pikm, and Bph29. Compared with those observed in their recurrent parents, CH121TJH significantly increased the mortality of borers. The other two lines CH891TJH and R205XTJH are the same result. Three lines introduction of Pib and Pikm significantly reduced the area of rice blast lesions, and introduction of Bph29 significantly reduced seedling mortality from N. lugens. Introduction of the exogenous genes had relatively few effects on agronomic and yield traits of the original parents. These findings suggest that stacking of rice resistance genes through molecular marker-assisted backcross breeding can confer broad spectrum and multiple resistance in differently genetic backgrounds.

Molecular identification and efficacy assessment of a glufosinate-tolerant and brown planthopper-resistant transgenic rice line

Insect pests and weeds are the two major biotic factors affecting crop yield in the modern agricultural system. In this study, a brown planthopper (BPH) resistance gene (BPH9) and glufosinate tolerance gene (bar) were stacked into a single T-DNA cassette and transformed into an indica rice (Oryza sativa L.) line Guangzhan 63-4S. A stable transgenic line H23 with a single T-DNA insert was generated, with the T-DNA cassette located on chromosome 3. Field resistance trial using H23 revealed high tolerance to glufosinate and excellent resistance to BPH. These results propose H23 as valuable germplasm for BPH-resistance and glufosinate-tolerance breeding in rice.

Novel Homogeneous Anion Exchange Membranes for Reproducible and Sensitive Nucleic Acid Detection via Current-Voltage Characteristic Measurement

One-pot synthesis of novel hydrogel-based anion exchange membranes (AEMs), with only a single-phase monomer mixture, was used to eliminate surface heterogeneity and generate reproducible electroconvective microvortices in the over-limiting region of the current-voltage characteristic (CVC) curves. Diallyldimethylammonium chloride (DDA) was used as the main component to provide the cation charge groups, and 2-hydroxyethyl methacrylate (HEMA) and ethylene glycol dimethyl acrylate (EGDMA) were used as the auxiliary structure monomers. The uniform membrane structure allowed reproducible and sensitive DNA detection and quantification, as probe-target surface complexes can gate the ion flux and produce large voltage shifts in the over-limiting region. Suppressed membrane curvature due to controlled swelling is a crucial part to avoid the reduction of depletion region for maintaining the influence of target gene hybridization. Fourier-transform infrared (FTIR) spectroscopy verified the synthesized membrane structure, with a residual vinyl group that allows easy carboxylation via additional photografting reaction. Consequently, a significantly higher DNA probe functionalization efficiency is obtained on the homogeneous AEMs, evidenced by the increasing nitrogen element content and bonding via X-ray photoelectron spectroscopy (XPS). The DDA content was optimized to provide a sufficient coulomb force between AEM and nucleic acid backbone to promote the specific binding efficiency but without high dimensional swelling which might change the surface geometry and restrict the voltage shifting for sensing in the over-limiting region, and the optimal DDA/HEMA ratio was found to be 4/10. The synthesized AEM sensor for recombinant 35S promoter sequence identification exhibited a reproducible calibration standard curve with dynamic range between 30 fM and 1 μM and high selectivity with only 0.01 V shift for 1 μM nontarget oligo.

Selection of ideotype to increase yield potential of GM and non-GM rice cultivars

Using classical breeding, plant breeders envision a plant type whose yield they aim to enhance by selecting for individual traits to create model/ideal plants or ideotypes. To achieve this, those factors restricting yield need to be identified and controlled through the use of new technologies to achieve the desired ideotype. This study aimed to determine the ideotype of seven genetically modified (GM) and non-GM rice (Oryza sativa L.) cultivars. Field experiments were carried out in three isolated regions in the north of Iran under the Iranian bio-safety standard protocol. Four of the GM cultivars carried the cry1Ab gene in the vegetative stage while three non-GM cultivars served as the control. R² values showed that five, six and seven variables in Sari, Amol and Rasht regions accounted for 63 %, 52 % and 74 % of paddy yield variation, respectively. In the same three regions, paddy yield variation due to white heads accounted for 28.38 %, 8.45 % and 3.95 % of the total variation in paddy yield, respectively. The total estimated variation in paddy yield in Sari, Amol and Rasht was 1810.50, 2377.6 and 2176.47 kg ha^-1, respectively. Average data over the three regions indicated that highest loss in paddy yield was observed in non-GM 'Nemat', 'Khazar' and 'Tarom Hashemi'. GM cultivars derived from 'Khazar' showed significantly lower paddy yield loss than the non-GM parent. Dead heart, a condition that occurs in the vegetative stage in which the stem borer larva enters the stem and feeds on the growing shoot, causing the central shoot to dry, as well as white heads, which is a condition in which whole ear heads of adult plants become dry and yield chaffy grains, in all three regions were important variables contributing to paddy yield loss. In the future, producing GM rice resistant to striped stem borer with an active promoter in the reproductive growth stage might allow farmers to reduce a significant part of paddy yield loss resulting from white heads, which is directly negatively correlated with filled spikelets per panicle (R² = -0.57**), in order to achieve an ideotype.

Transgene Stacking as Effective Tool for Enhanced Disease Resistance in Plants

Introduction of more than one gene into crop plants simultaneously or sequentially, called transgene stacking, has been a more effective strategy for conferring higher and durable insect and disease resistance in transgenic plants than single-gene technology. Transgenes can be stacked against one or more pathogens or for traits such as herbicide tolerance or anthocyanin pigmentation. Polygenic agronomic traits can be improved by multiple gene transformation. The most widely engineered stacked traits are insect resistance and herbicide tolerance as these traits may lead to lesser use of pesticides, higher yield, and efficient control of weeds. In this review, we summarize transgene stacking of two or more transgenes into crops for different agronomic traits, potential applications of gene stacking, its limitations and future prospects.

The application of gene splitting technique for controlling transgene flow in rice

Controlling transgene flow in China is important, as this country is part of the center of origin of rice. A gene-splitting technique based on intein-mediated trans-splicing represents a new strategy for controlling transgene flow via biological measures. In this study, the G2-aroA gene which provides glyphosate tolerance was split into an N-terminal and a C-terminal region, which were then fused to intein N and intein C of the Ssp DnaE intein, ultimately forming EPSPSn:In and Ic:EPSPSc fusion genes, respectively. These fusion genes were subsequently transformed into the rice cultivar Zhonghua 11 via the Agrobacterium-mediated method. The two split gene fragments were then introduced into the same rice genome by genetic crossings. Glyphosate tolerance analysis revealed that the functional target protein was reconstituted by Ssp DnaE intein-mediated trans-splicing and that the resultant hybrid rice was glyphosate tolerant. The reassembly efficiency of the split gene fragments ranged from 67 to 91% at the molecular level, and 100% of the hybrid F1 progeny were glyphosate tolerant. Transgene flow experiments showed that when the split gene fragments are inserted into homologous chromosomes, the gene-splitting technique can completely avoid the escape of the target trait to the environment. This report is the first on the reassembly efficiency and effectiveness of transgene flow containment via gene splitting in rice. This study provides not only a new biological strategy for controlling rice transgene flow but also a new method for cultivating hybrid transgenic rice.