Non-transgenic Control Plants Research Articles

Breeding Maize Hybrids with Improved Drought Tolerance Using Genetic Transformation

Drought is considered the main agricultural menace, limiting the successful realization of land potential, and thereby reducing crop productivity worldwide. Therefore, breeding maize hybrids with improved drought tolerance via genetic manipulation is necessary. Herein, the multiple bud clumps of elite inbred maize lines, DH4866, Qi319, Y478 and DH9938, widely used in China, were transformed with the Escherichia coli betA gene encoding choline dehydrogenase (EC 1.1.99.1), a key enzyme in the biosynthesis of glycine betaine from choline, using Agrobacterium to generate betA transgenic lines. After 3–4 consecutive generations of self-pollination in these transgenic plants, progenies with a uniform appearance, excellent drought tolerance, and useful agricultural traits were obtained. We evaluated the drought tolerance of T4 progenies derived from these transgenic plants in the field under reduced irrigation. We found that a few lines exhibited much higher drought tolerance than the non-transformed control plants. Transgenic plants accumulated higher levels of glycine betaine and were relatively more tolerant to drought stress than the controls at both the germination and early seedling stages. The grain yield of the transgenic plants was significantly higher than that of the control plants after drought treatment. Drought-tolerant inbred lines were mated and crossed to create hybrids, and the drought tolerance of these transgenic hybrids was found to be enhanced under field conditions compared with those of the non-transgenic (control) plants and two other commercial hybrids in China. High yield and drought tolerance were achieved concurrently. These transgenic inbred lines and hybrids were useful in marginal and submarginal lands in semiarid and arid regions. The betA transgene can improve the viability of crops grown in soils with sufficient or insufficient water.

Molecular and physiological characterization of AIP1, encoding the acetolactate synthase regulatory subunit in rice

Flooding deprives plants of oxygen and thereby causes severe stress by interfering with energy production, leading to growth retardation. Enzymes and metabolites may help protect plants from waterlogging and hypoxic environmental conditions. Acetolactate synthase (ALS) is a key enzyme in the biosynthesis of branched-chain amino acids (BCAAs), providing the building blocks for proteins and various secondary metabolites. Additionally, under energy-poor conditions, free BCAAs can be used as an alternative energy source by mitochondria through a catabolic enzyme chain reaction. In this study, we characterized ALS-INTERACTING PROTEIN 1 (OsAIP1), which encodes the regulatory subunit of ALS in rice (Oryza sativa). This gene was expressed in all parts of the rice plant, and its expression level was significantly higher in submerged and low-oxygen environments. Rice transformants overexpressing OsAIP1 showed a higher survival rate under hypoxic stress than did non-transgenic control plants under the same conditions. The OsAIP1-overexpressing plants accumulated increased levels of BCAAs, demonstrating that OsAIP1 is an important factor in the hypoxia resistance mechanism. These results suggest that ALS proteins are part of a defense mechanism that improves the tolerance of plants to low-oxygen environments.

Factors influencing Agrobacterium-mediated genetic transformation efficiency in bread wheat (Triticum aestivum L.)

Assessment of the efficiency of Agrobacterium tumefaciens mediated transformation in four bread wheat varieties was focused and upon optimization of experiments done to obtain tangible results. The four varieties, Fielder, Navojoa, Baj and Kachu/saul, were transformed with optimized protocols and randomly selected from a selection medium amalgamated with phosphinothricin (Glufosinate). Initially, the variety Fielder has proceeded with 36 different concentrations of synthetic auxins 2,4-D and picloram as 36 treatments. The treatment 30 (48 μg of 2,4-D and 64 μg of picloram) has shown higher efficiency and is comparable in terms of the three traits studied. Additionally, antioxidants and growth regulators were adjusted to obtain better results towards reasonable transformation frequency. Additional varieties were also tested and selected against the selectable marker PPT based on the optimization for the variety Fielder. Selected genotypes were subjected for gusA or Bar gene PCR amplification. The result revealed the frequency of transgenesis in the range of 60 to 70% with the varieties studied. However, the whole experiment needs further repetitions for confirmatory results. Transgenic genotypes of the Fielder variety showed moderate to strong GUS expression in leaves, anthers, seeds, seed coats, and roots compared to non-transgenic control plant tissues. PPT leaf painting assay showed the lack of necrosis on the painted area of leaves in transgenic genotypes compared to the non-transgenic ones.

Transgenic expression of Arabidopsis ELONGATION FACTOR-TU RECEPTOR (AtEFR) gene in banana enhances resistance against Xanthomonas campestris pv. musacearum.

Banana Xanthomonas wilt (BXW) caused by Xanthomonas campestris pv. musacearum (Xcm) is a severe bacterial disease affecting banana production in East and Central Africa, where banana is cultivated as a staple crop. Classical breeding of banana is challenging because the crop is clonally propagated and has limited genetic diversity. Thus, genetic engineering serves as a viable alternative for banana improvement. Studies have shown that transfer of the elongation factor Tu receptor gene (AtEFR) from Arabidopsis thaliana to other plant species can enhance resistance against bacterial diseases. However, AtEFR activity in banana and its efficacy against Xcm has not been demonstrated. In this study, transgenic events of banana (Musa acuminata) cultivar dwarf Cavendish expressing the AtEFR gene were generated and evaluated for resistance against Xcm under greenhouse conditions. The transgenic banana events were responsive to the EF-Tu-derived elf18 peptide and exhibited enhanced resistance to BXW disease compared to non-transgenic control plants. This study suggests that the functionality of AtEFR is retained in banana with the potential of enhancing resistance to BXW under field conditions.

Improved salt-tolerance of transgenic soybean by stable over-expression of AhBADH gene from Atriplex hortensis.

The salt-tolerance of transgenic soybean cleared for environmental release was improved by stable over-expression of AhBADH gene from Atriplex hortensis, which was demonstrated through molecular analysis and field experiments. An effective strategy for increasing the productivity of major crops under salt stress conditions is the development of transgenics that harbor genes responsible for salinity tolerance. Betaine aldehyde dehydrogenase (BADH) is a key enzyme involved in the biosynthesis of the osmoprotectant, glycine betaine (GB), and osmotic balance in plants, and several plants transformed with BADH gene have shown significant improvements in salt tolerance. However, very few field-tested transgenic cultivars have been reported, as most of the transgenic studies are limited to laboratory or green house experiments. In this study, we demonstrated through field experiments that AhBADH from Atriplex hortensis confers salt tolerance when transformed into soybean (Glycine max L.). AhBADH was successfully introduced into soybean by Agrobacterium mediated transformation. A total of 256 transgenic plants were obtained, out of which 47 lines showed significant enhancement of salt tolerance compared to non-transgenic control plants. Molecular analyses of the transgenic line TL2 and TL7 with the highest salt tolerance exhibited stable inheritance and expression of AhBADH in progenies with a single copy insertion. TL1, TL2 and TL7 exhibited stable enhanced salt tolerance and improved agronomic traits when subjected to 300mM NaCl treatment. Currently, the transgenic line TL2 and TL7 with stable enhanced salt tolerance, which have been cleared for environmental release, are under biosafety assessment. TL 2 and TL7 stably expressing AhBADH could then be applied in commercial breeding experiments to genetically improve salt tolerance in soybean.

Transformation and expressional studies of GaZnF gene to improve drought tolerance in Gossypium hirsutum

Drought stress is the major limiting factor in plant growth and production. Cotton is a significant crop as textile fiber and oilseed, but its production is generally affected by drought stress, mainly in dry regions. This study aimed to investigate the expression of Zinc finger transcription factor’s gene (GaZnF) to enhance the drought tolerance in Gossypium hirsutum. Sequence features of the GaZnF protein were recognized through different bioinformatics tools like multiple sequence alignment analysis, phylogenetic tree for evolutionary relationships, Protein motifs, a transmembrane domain, secondary structure and physio-chemical properties indicating that GaZnF is a stable protein. CIM-482, a local Gossypium hirsutum variety was transformed with GaZnF through Agrobacterium-mediated transformation method with 2.57% transformation efficiency. The integration of GaZnF was confirmed through Southern blot showing 531 bp, and Western blot indicated a 95 kDa transgene-GUS fusion band in transgenic plants. The normalized real-time expression analysis revealed the highest relative fold spatial expression of cDNA of GaZnF within leaf tissues at vegetative and flowering stages under drought stress. Morphological, physiological and biochemical parameters of transgenic cotton plants at 05- and 10-day drought stress was higher than those of non-transgenic control plants. The values of fresh and dry biomass, chlorophyll content, photosynthesis, transpiration rate, and stomatal conductance reduced in GaZnF transgenic cotton plants at 05- and 10-day drought stress, but their values were less low in transgenic plants than those of non-transgenic control plants. These findings showed that GaZnF gene expression in transgenic plants could be a valuable source for the development of drought-tolerant homozygous lines through breeding.

Overexpression of soybean trypsin inhibitor genes decreases defoliation by corn earworm (Helicoverpa zea) in soybean (Glycine max) and Arabidopsis thaliana.

Trypsin inhibitors (TIs) are widely distributed in plants and are known to play a protective role against herbivores. TIs reduce the biological activity of trypsin, an enzyme involved in the breakdown of many different proteins, by inhibiting the activation and catalytic reactions of proteins. Soybean (Glycine max) contains two major TI classes: Kunitz trypsin inhibitor (KTI) and Bowman-Birk inhibitor (BBI). Both genes encoding TI inactivate trypsin and chymotrypsin enzymes, which are the main digestive enzymes in the gut fluids of Lepidopteran larvae feeding on soybean. In this study, the possible role of soybean TIs in plant defense against insects and nematodes was investigated. A total of six TIs were tested, including three known soybean trypsin inhibitors (KTI1, KTI2 and KTI3) and three genes encoding novel inhibitors identified in soybean (KTI5, KTI7, and BBI5). Their functional role was further examined by overexpression of the individual TI genes in soybean and Arabidopsis. The endogenous expression patterns of these TI genes varied among soybean tissues, including leaf, stem, seed, and root. In vitro enzyme inhibitory assays showed significant increase in trypsin and chymotrypsin inhibitory activities in both transgenic soybean and Arabidopsis. Detached leaf-punch feeding bioassays detected significant reduction in corn earworm (Helicoverpa zea) larval weight when larvae fed on transgenic soybean and Arabidopsis lines, with the greatest reduction observed in KTI7 and BBI5 overexpressing lines. Whole soybean plant greenhouse feeding bioassays with H. zea on KTI7 and BBI5 overexpressing lines resulted in significantly reduced leaf defoliation compared to non-transgenic plants. However, bioassays of KTI7 and BBI5 overexpressing lines with soybean cyst nematode (SCN, Heterodera glycines) showed no differences in SCN female index between transgenic and non-transgenic control plants. There were no significant differences in growth and productivity between transgenic and non-transgenic plants grown in the absence of herbivores to full maturity under greenhouse conditions. The present study provides further insight into the potential applications of TI genes for insect resistance improvement in plants.

Raffinose positively regulates maize drought tolerance by reducing leaf transpiration.

Drought stress is one of the major constraints of global crop production. Raffinose, a non-reducing trisaccharide, has been considered to regulate positively the plant drought stress tolerance; however, evidence that augmenting raffinose production in leaves results in enhanced plant drought stress tolerance is lacking. The biochemical mechanism through which raffinose might act to mitigate plant drought stress remains unidentified. ZmRAFS encodes Zea mays RAFFINOSE SYNTHASE, a key enzyme that transfers galactose from the galactoside galactinol to sucrose for raffinose production. Overexpression of ZmRAFS in maize increased the RAFS protein and the raffinose content and decreased the water loss of leaves and enhanced plant drought stress tolerance. The biomass of the ZmRAFS overexpressing plants was similar to that of non-transgenic control plants when grown under optimal conditions, but was significantly greater than that of non-transgenic plants when grown under drought stress conditions. In contrast, the percentage of water loss of the detached leaves from two independent zmrafs mutant lines, incapable of synthesizing raffinose, was greater than that from null segregant controls and this phenomenon was partially rescued by supplementation of raffinose to detached zmrafs leaves. In addition, while there were differences in water loss among different maize lines, there was no difference in stomata density or aperture. Taken together, our work demonstrated that overexpression of the ZmRAFS gene in maize, in contrast to Arabidopsis, increased the raffinose content in leaves, assisted the leaf to retain water, and enhanced the plant drought stress tolerance without causing a detectable growth penalty.

Stable In-Planta Transformation System For Egyptian Sesame (Sesamum indicum L.) cv. Sohag 1

ABSTRACT Sesame (Sesamum indicum L.) is an important oil crop and one of the oldest-known oil crops to humankind. Sesame has excellent nutritional and therapeutic properties; it is rich in important fatty acids, protein, fiber, and vital minerals. Oil percentage varies among different genotypes but generally accounts for more than 50% of the seed’s dry weight. To meet the increasing demand for vegetable oil production worldwide, expanding the cultivation of oil crops in newly reclaimed areas worldwide is essential. Molecular breeding is an expeditious approach for varietal improvement but requires efficient transgenesis. Published sesame transformation methods are highly genus-specific, tedious, and involve preparing and testing different media and explants. We produced transgenic sesame plants using a stable, noninvasive, and robust Agrobacterium tumefaciens transformation method. Leaves and flowers excised from the T0 plants at different developmental stages were PCR screened, and 61/93 seedlings were found to be PCR positive. T1 seeds resulting from two lines were germinated in a biocontainment greenhouse facility and screened using PCR, basta leaf painting, and spraying fully matured plants with basta herbicide (0.02 mg/l); non-transgenic segregants and control non-transgenic plants were severely damaged, and eventually died, while transgenic plants were not affected by the Basta spraying. RT-PCR on T1 plants indicated the presence of Bar transcripts in T1 progeny. Furthermore, RT-PCR using NPTII primers did not result in any amplification in transgenic sesame plants (NPTII is present in the vector but not in the T-DNA region) indicating that the transgenic sesame plants were not an Agrobacterium-contaminant.

Production of proinflammatory cytokines by expressing Newcastle disease vaccine candidates in corn

The efficacy of a plant-based edible vaccine produced in maize by expression of F and HN immunogenic proteins under a seed-specific promoter against Newcastle disease virus (NDV) genotype VII was assessed using cytokine-mediated cellular immune responses in chickens. Using real-time PCR, the mRNA expression of transgenic maize plants was compared to non-transgenic control plants on a relative basis. F and HN genes mRNA expression was found to be 20 and 60 times higher in corn seeds than in leaves, respectively. In maize seeds, 35 µg ml−1 of F protein, or 0.6 percent of total protein, and 41 µg ml−1 of HN protein, or 0.85 percent of total protein, were found using ELISA. The boost in cell-mediated immune response was evaluated in chickens fed with transgenic corn seeds in comparison with control groups. The qPCR analysis showed an increase in the expression of IL-1 (Interleukin-1), IL-2 (Interleukin-2), IL-6 (Interleukin-6), IL-8 (Interleukin-8), IL-10 (Interleukin-10), IL-15 (interleukin-15), Interferon-α, Interferon-β, Interferon-γ, and CCL3 when evaluated at 0, 7th, 14th, 21st, 28th and 35th day in chickens receiving transgenic diet as compared to group 1 receiving non-transgenic diet. The increase in cytokines production was comparable with group 3 immunized with conventional market vaccine. Furthermore, anti-NDV antibodies were also found in the serum of chickens given maize containing immunogenic proteins, but not in the serum of chickens given a regular normal diet, illustrating the antibodies’ specificity produced after feeding. The results demonstrate that transgenic maize consumed orally strongly stimulates the expression of cytokine genes related to cell-mediated immunity, just like commercial vaccines. These results further suggest that these cytokines may be important in initiating cellular immune responses in response to NDV infection.

Tissue specific expression of bacterial cellulose synthase (Bcs) genes improves cotton fiber length and strength

Fiber growing inside the cotton bolls is a highly demandable product and its quality is key to the success of the textile industry. Despite the various efforts to improve cotton fiber staple length Pakistan has to import millions of bales to sustain its industrial needs. To improve cotton fiber quality Bacterial cellulose synthase (Bcs) genes (acsA, acsB) were expressed in a local cotton variety CEMB-00. In silico studies revealed a number of conserved domains both in the cotton-derived and bacterial cellulose synthases which are essential for the cellulose synthesis. Transformation efficiency of 1.27% was achieved by using Agrobacterium shoot apex cut method of transformation. The quantitative mRNA expression analysis of the Bcs genes in transgenic cotton fiber was found to be many folds higher during secondary cell wall synthesis stage (35 DPA) than the expression during elongation phase (10 DPA). Average fiber length of the transgenic cotton plant lines S-00–07, S-00–11, S-00–16 and S-00–23 was calculated to be 13.02% higher than that of the non-transgenic control plants. Likewise, the average fiber strength was found to be 20.92% higher with an enhanced cellulose content of 22.45%. The mutated indigenous cellulose synthase genes of cotton generated through application of CRISPR/Cas9 resulted in 6.03% and 12.10% decrease in fiber length and strength respectively. Furthermore, mature cotton fibers of transgenic cotton plants were found to have increased number of twists with smooth surface as compared to non-transgenic control when analyzed under scanning electron microscope. XRD analysis of cotton fibers revealed less cellulose crystallinity index in transgenic cotton fibers as compared to control fibers due to deposition of more amorphous cellulose in transgenic fibers as a result of Bcs gene expression. This study paved the way towards unraveling the fact that Bcs genes influence cellulose synthase activity and this enzyme helps in determining the fate of cotton fiber length and strength.

Producing fluorescent plants to lure and trap insect pests.

Producing fluorescent plants to lure and trap insect pests.

Heterologous expression of cry3Bb1 and cry3 genes for enhanced resistance against insect pests in cotton

Transgenic technology played a crucial role in developing insect-resistant plants resulting in the reduced application of pesticides. This article reports the expression of two cry proteins (Cry3Bb1 and Cry3) in cotton for enhanced resistance against chewing insect pests. The aforementioned genes were synthetically developed and were cloned under appropriate regulatory sequences followed by transformation into Eagle-2 genotype (Gossypium hirsutum) of cotton through shoot apex-cut Agro-infiltration. The transgene integration was validated by polymerase chain reaction using primers flanking the aforementioned cry genes. Transgene expression was assessed by qRT-PCR using GADPH as a reference gene. The relative fold expression analyses revealed the highest expression of the transgene(s) in M1 plants, which is a 4.5-fold expression (Cry3 + Cry3Bb1) followed by M3 (fold expression, 3.0) (Cry3Bb1) and M2 (fold expression, 2.5) (Cry3) transformants of cotton. The confirmed transgenic plants were exposed to insect pests, pink bollworm (Pectinophora gossypiella), and army bollworm (Helicoverpa armigera). Bioassay results revealed that 60% mortality was observed against pink bollworm, and 75% mortality was observed against army bollworm in transgenic plants containing both Cry3Bb1 and Cry3 genes (M1 transgenic plants). In M2 transgenic plants containing only the Cry3Bb1 gene, the mortality was observed to be 40% in the pink bollworm population, whereas 45% mortality was observed in the army bollworm population. In the case of M3 transgenic plants containing single gene-Cry3, the mortality was 20% in the pink bollworm population, whereas 30% mortality was observed in the army bollworm population. Almost no mortality was observed in non-transgenic Eagle-2 control plants. Hence, the developed cotton transformants have improved resistance against chewing insect pests.

Aspartic protease inhibitor enhances resistance to potato virus Y and A in transgenic potato plants

BackgroundViruses are the major threat to commercial potato (Solanum tuberosum) production worldwide. Because viral genomes only encode a small number of proteins, all stages of viral infection rely on interactions between viral proteins and host factors. Previously, we presented a list of the most important candidate genes involved in potato plants’ defense response to viruses that are significantly activated in resistant cultivars. Isolated from this list, Aspartic Protease Inhibitor 5 (API5) is a critical host regulatory component of plant defense responses against pathogens. The purpose of this study is to determine the role of StAPI5 in defense of potato against potato virus Y and potato virus A, as well as its ability to confer virus resistance in a transgenic susceptible cultivar of potato (Desiree). Potato plants were transformed with Agrobacterium tumefaciens via a construct encoding the potato StAPI5 gene under the control of the Cauliflower mosaic virus (CaMV) 35S promoter.ResultsTransgenic plants overexpressing StAPI5 exhibited comparable virus resistance to non-transgenic control plants, indicating that StAPI5 functions in gene regulation during virus resistance. The endogenous StAPI5 and CaMV 35S promoter regions shared nine transcription factor binding sites. Additionally, the net photosynthetic rate, stomatal conductivity, and maximum photochemical efficiency of photosystem II were significantly higher in virus-infected transgenic plants than in wild-type plants.ConclusionOverall, these findings indicate that StAPI5 may be a viable candidate gene for engineering plant disease resistance to viruses that inhibit disease development.

Overexpression of ZmSPL12 confers enhanced lodging resistance through transcriptional regulation of D1 in maize.

Overexpression of ZmSPL12 confers enhanced lodging resistance through transcriptional regulation of D1 in maize.

Engineered resistance and risk assessment associated with insecticidal and weeds resistant transgenic cotton using wister rat model

Stacking multiple genes into cotton crop to cop up multiple biotic stresses such as insects and weeds is a promising tool to save crop from losses. Transgenic cotton variety, VH-289, with double Bt and cp4EPSPS genes under the control of 35S promoter was used for the expression analyses and biosafety studies. The transgenic cotton plants were screened through PCR amplification of fragments, 1.7 kb for Cry1Ac, 582 bp for Cry2A and 250 bp for cp4EPSPS; which confirmed the presence of all genes transformed in transgenic cotton. The Cry1Ac + Cry2A and cp4EPSPS proteins were quantified through ELISA in transgenic cotton plants. The Glyphosate assay performed by spraying 1900 mL per acre of glyphosate Roundup further confirmed complete survival of transgenic cotton plants as compared to the non-transgenic cotton plants and all weeds. Similarly, insect infestation data determined that almost 99% insect mortality was observed in controlled field grown transgenic cotton plants as compared to the non-transgenic control plants. Evaluation of effect of temperature and soil nutrients availability on transgene expression in cotton plants was done at two different cotton growing regions, Multan and Lahore, Pakistan and results suggested that despite of higher temperature in Multan field, an increased level of Cry and cp4EPSPS proteins was recorded due to higher soil organic matter availability compared to Lahore field. Before commercialization of any transgenic variety its biosafety study is mandatory so, a 90 days biosafety study of the transgenic cotton plants with 40% transgenic cottonseeds in standard diet showed no harmful effect on wister rat model when studied for liver function, renal function and serum electrolyte.

Response of Transgenic Potato Plants Expressing Heterologous Genes of ∆9- or ∆12-Acyl-lipid Desaturases to Phytophthora infestans Infection.

Late blight is one of the most economically important diseases affecting potato and causing a significant loss in yield. The development of transgenic potato plants with enhanced resistance to infection by Phytophthora infestans may represent a possible approach to solving this issue. A comparative study of the leaf response in control potato plants (S.tuberosum L. cultivar Skoroplodnyi), control transgenic plants expressing the reporter gene of thermostable lichenase (transgenic licBM3 line) and transgenic plants expressing cyanobacterial hybrid genes ∆9-acyl-lipid desaturase (transgenic desC lines) and ∆12-acyl-lipid desaturase (transgenic desA lines) to infection with P. infestans has been performed. The expression of desaturase genes in potato plants enhanced their tolerance to potato late blight agents as compared with the control. The lipid peroxidation level raised in the leaves of the control and transgenic desA plants on third day after inoculation with P. infestans zoospores and remained the same in the transgenic desC plants. The number of total phenolic compounds was increased as early as on the second day after infection in all studied variants and continued to remain the same, except for transgenic desC plants. Accumulation of flavonoids, the main components of the potato leaf phenolic complex, raised on the second day in all studied variants, remained unchanged on the third day in the control plants and decreased in most transgenic plants expressing desaturase genes. The results obtained in our study demonstrate that the expression of genes of Δ9- and Δ12-acyl-lipid desaturases in potato plants enhanced their resistance to P. infestans as compared with the control non-transgenic plants due to concomitant accumulation of phenolic compounds, including flavonoids, in the leaves. All these changes were more pronounced in transgenic desC plants, which indicates that the Δ9-acyllipid desaturase gene appears to be a potential inducer of the production of biological antioxidants in plant cells.

Rice microRNA171f/SCL6 module enhances drought tolerance by regulation of flavonoid biosynthesis genes.

Plants have evolved sophisticated defense systems to enhance drought tolerance. These include the microRNA (miRNA) group of small noncoding RNAs that act as post‐transcriptional regulators; however, details of the mechanisms by which they confer drought tolerance are not well understood. Here, we show that osa‐MIR171f, a member of osa‐MIR171 gene family, is mainly expressed in response to drought stress and regulates the transcript levels of SCARECROW‐LIKE6‐I (SCL6‐I) and SCL6‐II in rice ( Oryza sativa ). The SCL6 genes are known to be involved in shoot branching and flag leaf morphology. Osa‐MIR171f‐overexpressing (osa‐MIR171f‐OE) transgenic plants showed reduced drought symptoms compared with non‐transgenic (NT) control plants under both field drought and polyethylene glycol (PEG)‐mediated dehydration stress conditions. Transcriptome analysis of osa‐MIR171f‐OE plants and osa‐mir171f‐knockout (K/O) lines generated by clustered regularly interspaced short palindromic repeats (CRISPR/Cas9) revealed that osa‐mature‐miR171a‐f (osa‐miR171) regulates the expression of flavonoid biosynthesis genes, consequently leading to drought tolerance. This upregulation in the osa‐MIR171f‐OE plants, which did not occur in NT control plants, was observed under both normal and drought conditions. Our findings indicate that osa‐miR171 plays a role in drought tolerance by regulating SCL6‐I and SCL6‐II transcript levels.

Overexpression of Cinnamoyl-CoA Reductase 2 in Brassica napus Increases Resistance to Sclerotinia sclerotiorum by Affecting Lignin Biosynthesis

Sclerotinia sclerotiorum causes severe yield and economic losses for many crop and vegetable species, especially Brassica napus. To date, no immune B. napus germplasm has been identified, giving rise to a major challenge in the breeding of Sclerotinia resistance. In the present study, we found that, compared with a Sclerotinia-susceptible line (J902), a Sclerotinia-resistant line (J964) exhibited better xylem development and a higher lignin content in the stems, which may limit the invasion and spread of S. sclerotiorum during the early infection period. In addition, genes involved in lignin biosynthesis were induced under S. sclerotiorum infection in both lines, indicating that lignin was deposited proactively in infected tissues. We then overexpressed BnaC.CCR2.b, which encodes the first rate-limiting enzyme (cinnamoyl-CoA reductase) that catalyzes the reaction of lignin-specific pathways, and found that overexpression of BnaC.CCR2.b increased the lignin content in the stems of B. napus by 2.28–2.76% under normal growth conditions. We further evaluated the Sclerotinia resistance of BnaC.CCR2.b overexpression lines at the flower-termination stage and found that the disease lesions on the stems of plants in the T2 and T3 generations decreased by 12.2–33.7% and 32.5–37.3% compared to non-transgenic control plants, respectively, at 7days post-inoculation (dpi). The above results indicate that overexpression of BnaC.CCR2.b leads to an increase in lignin content in the stems, which subsequently leads to increased resistance to S. sclerotiorum. Our findings demonstrate that increasing the lignin content in the stems of B. napus is an important strategy for controlling Sclerotinia.

Transgenic japonica rice expressing the cry1C gene is resistant to striped stem borers in Northeast China

Rice production and quality are seriously affected by the lepidopteran pest, striped stem borer (SSB), in Northeast China. In this study, a synthetic cry1C gene encoding Bacillus thuringiensis (Bt) δ-endotoxin, which is toxic to lepidopteran pest, was transformed into a japonica rice variety (Jigeng 88) in Northeast China by Agrobacterium-mediated transformation. Through molecular detection and the Basta resistance germination assay, a total of 16 single-copy homozygous transgenic lines were obtained from 126 independent transformants expressing cry1C. Finally, four cry1C-transgenic lines (JL16, JL23, JL41, and JL42) were selected by evaluation of the Cry1C protein level, insect-resistance and agronomic traits. The cry1C-transgenic lines had higher resistance to SSB and higher yield compared with non-transgenic (NT) control plants. T-DNA flanking sequence analysis of the transgenic line JL42 showed that the cry1C gene was inserted into the intergenic region of chromosome 11, indicating that its insertion may not interfere with the genes near insertion site. In summary, this study developed four cry1C-transgenic japonica rice lines with high insect resistance and high yield. They can be used as insect-resistant germplasm materials to overcome the problem of rice yield reduction caused by SSB and reduce the use of pesticides in Northeast China.