Development and Characterization of Transgenic Sugarcane with Insect Resistance and Herbicide Tolerance

Transgenic early japonica rice: Integration and expression characterization of stem borer resistance Bt gene

BACKGROUND

Transgenic insect-resistant rice offers an environmentally friendly approach to mitigate yield losses caused by lepidopteran pests, such as stem borers. Bt (Bacillus thuringiensis) genes encode insecticidal proteins and are widely used to confer insect resistance to genetically modified crops. This study investigated the integration, inheritance, and expression characteristics of codon-optimised synthetic Bt genes, cry1C* and cry2A*, in transgenic early japonica rice lines.

METHODS

The early japonica rice cultivar, Songgeng 9 (Oryza sativa), was transformed with cry1C* or cry2A*, which are driven by the ubi promoter via Agrobacterium tumefaciens-mediated transformation. Molecular analyses, including quantitative PCR (qPCR), enzyme-linked immunosorbent assay (ELISA), and Southern blot analysis were performed to confirm transgene integration, inheritance, transcriptional levels, and protein expression patterns across different tissues and developmental stages.

RESULTS

Stable transgenic early japonica lines exhibiting single-copy transgene integration were established. Transcriptional analysis revealed variations in Bt gene expression among lines, tissues, and growth stages, with higher expression levels observed in leaves than in other organs. Notably, cry2A* exhibited consistently higher mRNA and protein levels than cry1C* across all examined tissues and developmental time points. Bt protein accumulation followed the trend of leaves > stem sheaths > young panicles > brown rice, with peak expression during the filling stage in the vegetative tissues.

CONCLUSIONS

Synthetic cry2A* displayed markedly elevated transcription and translation compared to cry1C* in the transgenic early japonica rice lines examined. Distinct spatiotemporal patterns of Bt gene expression were elucidated, providing insights into the potential insect resistance conferred by these genes in rice. These findings will contribute to the development of insect-resistant japonica rice varieties and facilitate the rational deployment of Bt crops.

Whole-genome sequencing of a worldwide collection of sugarcane cultivars (Saccharum spp.) reveals the genetic basis of cultivar improvement

Sugarcane is the main source of sugar worldwide, and 80% of the sucrose production comes from sugarcane. However, the genetic differentiation and basis of agronomic traits remain obscure. Here, we sequenced the whole-genome of 219 elite worldwide sugarcane cultivar accessions. A total of approximately 6 million high-quality genome-wide single nucleotide polymorphisms (SNPs) were detected. A genome-wide association study identified a total of 2198 SNPs that were significantly associated with sucrose content, stalk number, plant height, stalk diameter, cane yield, and sugar yield. We observed homozygous tendency of favor alleles of these loci, and over 80% of cultivar accessions carried the favor alleles of the SNPs or haplotypes associated with sucrose content. Gene introgression analysis showed that the number of chromosome segments from Saccharum spontaneum decreased with the breeding time of cultivars, while those from S. officinarum increased in recent cultivars. A series of selection signatures were identified in sugarcane improvement procession, of which 104 were simultaneously associated with agronomic traits and 45 of them were mainly associated with sucrose content. We further proposed that as per sugarcane transgenic experiments, ShN/AINV3.1 plays a positive role in increasing stalk number, plant height, and stalk diameter. These findings provide comprehensive resources for understanding the genetic basis of agronomic traits and will be beneficial to germplasm innovation, screening molecular markers, and future sugarcane cultivar improvement.

Genetic Engineering for Enhancing Sugarcane Tolerance to Biotic and Abiotic Stresses

Sugarcane, a vital cash crop, contributes significantly to the world's sugar supply and raw materials for biofuel production, playing a significant role in the global sugar industry. However, sustainable productivity is severely hampered by biotic and abiotic stressors. Genetic engineering has been used to transfer useful genes into sugarcane plants to improve desirable traits and has emerged as a basic and applied research method to maintain growth and productivity under different adverse environmental conditions. However, the use of transgenic approaches remains contentious and requires rigorous experimental methods to address biosafety challenges. Clustered regularly interspaced short palindromic repeat (CRISPR) mediated genome editing technology is growing rapidly and may revolutionize sugarcane production. This review aims to explore innovative genetic engineering techniques and their successful application in developing sugarcane cultivars with enhanced resistance to biotic and abiotic stresses to produce superior sugarcane cultivars.

Factors affecting the production of sugarcane yield and sucrose accumulation: suggested potential biological solutions

Environmental stresses are the main constraints on agricultural productivity and food security worldwide. This issue is worsened by abrupt and severe changes in global climate. The formation of sugarcane yield and the accumulation of sucrose are significantly influenced by biotic and abiotic stresses. Understanding the biochemical, physiological, and environmental phenomena associated with these stresses is essential to increase crop production. This review explores the effect of environmental factors on sucrose content and sugarcane yield and highlights the negative effects of insufficient water supply, temperature fluctuations, insect pests, and diseases. This article also explains the mechanism of reactive oxygen species (ROS), the role of different metabolites under environmental stresses, and highlights the function of environmental stress-related resistance genes in sugarcane. This review further discusses sugarcane crop improvement approaches, with a focus on endophytic mechanism and consortium endophyte application in sugarcane plants. Endophytes are vital in plant defense; they produce bioactive molecules that act as biocontrol agents to enhance plant immune systems and modify environmental responses through interaction with plants. This review provides an overview of internal mechanisms to enhance sugarcane plant growth and environmental resistance and offers new ideas for improving sugarcane plant fitness and crop productivity.

Establishment of an Efficient Sugarcane Transformation System via Herbicide-Resistant CP4-EPSPS Gene Selection

Sugarcane (Saccharum spp.), a major cash crop that is an important source of sugar and bioethanol, is strongly influenced by the impacts of biotic and abiotic stresses. The intricate polyploid and aneuploid genome of sugarcane has shown various limits for conventional breeding strategies. Nonetheless, biotechnological engineering currently offers the best chance of introducing commercially significant agronomic features. In this study, an efficient Agrobacterium-mediated transformation system that uses the herbicide-resistant CP4-EPSPS gene as a selection marker was developed. Notably, all of the plants that were identified by PCR as transformants showed significant herbicide resistance. Additionally, this transformation protocol also highlighted: (i) the high yield of transgenic lines from calli (each gram of calli generated six transgenic lines); (ii) improved selection; and (iii) a higher transformation efficiency. This protocol provides a reliable tool for a routine procedure for the generation of resilient sugarcane plants.

CRISPR technology towards genome editing of the perennial and semi-perennial crops citrus, coffee and sugarcane

Gene editing technologies have opened up the possibility of manipulating the genome of any organism in a predicted way. CRISPR technology is the most used genome editing tool and, in agriculture, it has allowed the expansion of possibilities in plant biotechnology, such as gene knockout or knock-in, transcriptional regulation, epigenetic modification, base editing, RNA editing, prime editing, and nucleic acid probing or detection. This technology mostly depends on in vitro tissue culture and genetic transformation/transfection protocols, which sometimes become the major challenges for its application in different crops. Agrobacterium-mediated transformation, biolistics, plasmid or RNP (ribonucleoprotein) transfection of protoplasts are some of the commonly used CRISPR delivery methods, but they depend on the genotype and target gene for efficient editing. The choice of the CRISPR system (Cas9, Cas12), CRISPR mechanism (plasmid or RNP) and transfection technique (Agrobacterium spp., PEG solution, lipofection) directly impacts the transformation efficiency and/or editing rate. Besides, CRISPR/Cas technology has made countries rethink regulatory frameworks concerning genetically modified organisms and flexibilize regulatory obstacles for edited plants. Here we present an overview of the state-of-the-art of CRISPR technology applied to three important crops worldwide (citrus, coffee and sugarcane), considering the biological, methodological, and regulatory aspects of its application. In addition, we provide perspectives on recently developed CRISPR tools and promising applications for each of these crops, thus highlighting the usefulness of gene editing to develop novel cultivars.

From Transgenesis to Genome Editing in Crop Improvement: Applications, Marketing, and Legal Issues

The biotechnological approaches of transgenesis and the more recent eco-friendly new breeding techniques (NBTs), in particular, genome editing, offer useful strategies for genetic improvement of crops, and therefore, recently, they have been receiving increasingly more attention. The number of traits improved through transgenesis and genome editing technologies is growing, ranging from resistance to herbicides and insects to traits capable of coping with human population growth and climate change, such as nutritional quality or resistance to climatic stress and diseases. Research on both technologies has reached an advanced stage of development and, for many biotech crops, phenotypic evaluations in the open field are already underway. In addition, many approvals regarding main crops have been granted. Over time, there has been an increase in the areas cultivated with crops that have been improved through both approaches, but their use in various countries has been limited by legislative restrictions according to the different regulations applied which affect their cultivation, marketing, and use in human and animal nutrition. In the absence of specific legislation, there is an on-going public debate with favorable and unfavorable positions. This review offers an updated and in-depth discussion on these issues.

Genetic engineering: an efficient approach to mitigating biotic and abiotic stresses in sugarcane cultivation

Abiotic stresses are the foremost limiting factors for crop productivity. Crop plants need to cope with adverse external pressure caused by various environmental conditions with their intrinsic biological mechanisms to keep their growth, development, and productivity. Climate-resilient, high-yielding crops need to be developed to maintain sustainable food supply. Over the last decade, understanding of the genetic complexity of agronomic traits in sugarcane has prompted the integrated application of genetic engineering to address specific biological questions. Genes for adaptation to environmental stress and yield enhancement traits are being determined and introgressed to develop elite sugarcane cultivars with improved characteristics through genetic engineering approaches. Here, we discuss the advancement to provide a reference for future sugarcane (Saccharum spp.) genetic engineering.

A short review on sugarcane: its domestication, molecular manipulations and future perspectives

Sugarcane (Saccharum spp.) is a special crop plant that underwent anthropogenic evolution from a wild grass species to an important food, fodder, and energy crop. Unlike any other grass species which were selected for their kernels, sugarcane was selected for its high stem sucrose accumulation. Flowering in sugarcane is not favored since flowering diverts the stored sugar resources for the reproductive and developmental energy needs. Cultivars are vegetatively propagated and sugarcane breeding is still essentially focused on conventional methods, since the knowledge of sugarcane genetics has lagged that of other major crops. Cultivar improvement has been extremely challenging due to its polyploidy and aneuploidy nature derived from a few interspecific hybridizations between Saccharum officinarum and Saccharum spontaneum, revealing the coexistence of two distinct genome organization modes in the modern variety. Alongside implementation of modern agricultural techniques, generation of hybrid clones, transgenics and genome edited events will help to meet the ever-growing bioenergy needs. Additionally, there are two common biotechnological approaches to improve plant stress tolerance, which includes marker-assisted selection (MAS) and genetic transformation. During the past two decades, the use of molecular approaches has contributed greatly to a better understanding of the genetic and biochemical basis of plant stress-tolerance and in some cases, it led to the development of plants with enhanced tolerance to abiotic stress. Hence, this review mainly intends on the events that shaped the sugarcane as what it is now and what challenges ahead and measures taken to further improve its yield, production and maximize utilization to beat the growing demands.

Breeding of virus-resistant transgenic sugarcane by the integration of the Pac1 gene

Various RNA viral diseases on sugarcane result in yield loss and decreased sugar content. Breeding new varieties with virus resistance is the main goal of the sugarcane breeding program. Both single-stranded and double-stranded RNA viruses generated a double-stranded RNA replicative form (RF) during the replication cycle progress. While double-stranded RNA-specific ribonuclease (PAC1) encoded by the Pac1 gene (from Schizosaccharomyces pombe) can recognize and degrade double-stranded RNA specifically without any sequence, the expression of PAC1 in transgenic sugarcane may successfully develop virus-resistant sugarcane. In this research, we first expressed the PAC1 in prokaryotic cells. Then, double-stranded RNA RF of sugarcane's streak mosaic virus (SCSMV) was artificially synthesized. The degradation activity of the PAC1 was successfully tested by mixing the PAC1 protein and the double-stranded RNA RF. After that, the Pac1 gene was ligated to a plant expression vector and was then introduced into a virus-sensitive sugarcane cultivar by using Agrobacterium tumefaciens-mediated transformation method. Transgenic plants were challenged by inoculating with SCSMV. Results showed that although all the transgenic lines were infected by SCSMV, the mosaic symptoms that appeared on the leaves were significantly milder than that of the wild type. All transgenic shoots showed significantly lower viral loads and attained greater heights than wild-type shoots. This research provided a new pathway for breeding new varieties of sugarcane with virus resistance.

Impact of Agroclimatic Variables on Proteogenomics in Sugar Cane (Saccharum spp.) Plant Productivity

Sugar cane (Saccharum spp. hybrids) is a major crop for sugar and renewable bioenergy worldwide, grown in arid and semiarid regions. China, the world's fourth-largest sugar producer after Brazil, India, and the European Union, all share ∼80% of the global production, and the remaining ∼20% of sugar comes from sugar beets, mostly grown in the temperate regions of the Northern Hemisphere, also used as a raw material in production of bioethanol for renewable energy. In view of carboxylation strategies, sugar cane qualifies as one of the best C4 crop. It has dual CO2 concentrating mechanisms located in its unique Krantz anatomy, having dimorphic chloroplasts located in mesophylls and bundle sheath cells for integrated operation of C4 and C3 carbon fixation cycles, regulated by enzymes to upgrade/sustain an ability for improved carbon assimilation to acquire an optimum carbon economy by producing enhanced plant biomass along with sugar yield under elevated temperature and strong irradiance with improved water-use efficiency. These superior intrinsic physiological carbon metabolisms encouraged us to reveal and recollect the facts for moving ahead with the molecular approaches to reveal the expression of proteogenomics linked with plant productivity under abiotic stress during its cultivation in specific agrizones globally.

A Comprehensive Identification and Expression Analysis of VQ Motif-Containing Proteins in Sugarcane (Saccharum spontaneum L.) under Phytohormone Treatment and Cold Stress

The VQ motif-containing proteins play a vital role in various processes such as growth, resistance to biotic and abiotic stresses and development. However, there is currently no report on the VQ genes in sugarcane (Saccharum spp.). Herein, 78 VQ genes in Saccharum spontaneum were identified and classified into nine subgroups (I-IX) by comparative genomic analyses. Each subgroup had a similar structural and conservative motif. These VQ genes expanded mainly through whole-genome segmental duplication. The cis-regulatory elements (CREs) of the VQ genes were widely involved in stress responses, phytohormone responses and physiological regulation. The RNA-seq data showed that SsVQ gene expression patterns in 10 different samples, including different developmental stages, revealed distinct temporal and spatial patterns. A total of 23 SsVQ genes were expressed in all tissues, whereas 13 SsVQ genes were not expressed in any tissues. Sequence Read Archive (SRA) data showed that the majority of SsVQs responded to cold and drought stress. In addition, quantitative real-time PCR analysis showed that the SsVQs were variously expressed under salicylic acid (SA), jasmonic acid (JA), abscisic acid (ABA) and cold treatment. This study conducted a full-scale analysis of the VQ gene family in sugarcane, which could be beneficial for the functional characterization of sugarcane VQ genes and provide candidate genes for molecular resistance breeding in cultivated sugarcane in the future.

Modern Biotechnologies: Innovative and Sustainable Approaches for the Improvement of Sugarcane Tolerance to Environmental Stresses

Sugarcane (Saccharum spp.) is one of the most important industrial cash crops, contributing to the world sugar industry and biofuel production. It has been cultivated and improved from prehistoric times through natural selection and conventional breeding and, more recently, using the modern tools of genetic engineering and biotechnology. However, the heterogenicity, complex poly-aneuploid genome and susceptibility of sugarcane to different biotic and abiotic stresses represent impediments that require us to pay greater attention to the improvement of the sugarcane crop. Compared to traditional breeding, recent advances in breeding technologies (molecular marker-assisted breeding, sugarcane transformation, genome-editing and multiple omics technologies) can potentially improve sugarcane, especially against environmental stressors. This article will focus on efficient modern breeding technologies, which provide crucial clues for the engineering of sugarcane cultivars resistant to environmental stresses.

Genetic Engineering Approaches for Enhanced Insect Pest Resistance in Sugarcane

Sugarcane (Saccharum officinarum), a sugar crop commonly grown for sugar production all over the world, is susceptible to several insect pests attack in addition to bacterial, fungal and viral infections leading to substantial reductions in its yield. The complex genetic makeup and lack of resistant genes in genome of sugarcane have made the conventional breeding a difficult and challenging task for breeders. Using pesticides for control of the attacking insects can harm beneficial insects, human and other animals and the environment as well. As alternative and effective strategy for control of insect pests, genetic engineering has been applied for overexpression of cry proteins, vegetative insecticidal proteins (vip), lectins and proteinase inhibitors (PI). In addition, the latest biotechnological tools such as host-induced gene silencing (HIGS) and CRISPR/Cas9 can be employed for sustainable control of insect pests in sugarcane. In this review overexpression of the cry, vip, lectins and PI genes in transgenic sugarcane and their disease resistance potential is described.

hRNAi-mediated knock-down of Sphenophorus levis V-ATPase E in transgenic sugarcane (Saccharum spp interspecific hybrid) affects the insect growth and survival

Transgenic sugarcane expressing V-ATPase subunit E dsRNA affects growth and survival of Sphenophorus levis. Plants being sessile organisms are constantly confronted with several biotic and abiotic stresses. Sugarcane (Saccharum spp) is a major tropical crop widely cultivated for its sugar and other by-products. In Brazil, sugarcane plantations account for significant production losses due to Sphenophorus levis (sugarcane weevil) infestations. With the existing control measures being less effective, there arises a necessity for advanced strategies. Our bioassay injection experiments with V-ATPase E dsRNA in S. levis larvae showed significant mortality and reduction in transcription levels. Furthermore, we down-regulated the V-ATPase E gene of S. levis in transgenic sugarcane using an RNAi approach. The resultant RNAi transgenic lines exhibited reduction in larval growth and survival, without compromising plant performance under controlled environment. Our results illustrate that RNAi-mediated down-regulation of key genes is a promising approach in imparting resistance to sugarcane weevil.

Improvement of sugarcane for borer resistance using Agrobacterium mediated transformation of cry1Ac gene

The sugarcane (Saccharum X officinarum) is one of the most important crops used to produce sugar and raw material for biofuel in the world. One of the main causes for sucrose content and yield losses is the attack by insect. In this investigation, cry1Ac gene was introduced into sugarcane variety GT54-9(C9) using the Agrobacterium tumefaciens transformation method for transgenic sugarcane production presenting insect-resistance. The A. tumefaciens strain GV1303 including pARTcry1Ac vector was used for the production of transformed sugarcane. The Bacillus thuringiensis cry gene were successfully used to produce transgenic plants used for the improvement of both agronomic efficiency and product quality by acquiring insect resistance. PCR and Southern hybridization techniques were used to confirm the cry1Ac gene incorporation into sugarcane genome. Transformation percentage was 22.2% using PCR analysis with specific primers for cry1Ac and npt-II (Neomycin phosphotransferase) genes. The expression of cry1Ac gene was determined using reverse transcriptase polymerase chain reaction (RT-PCR), QuickStix test, and insect bioassays. Bioassays for transformed sugarcane plants showed high level of toxicity to Sesamia cretica giving 100% mortality of the larvae. Sugarcane insect resistance was improved significantly by using cry1Ac gene transformation.

Genetic Transformation of Sugarcane, Current Status and Future Prospects

Sugarcane (Saccharum spp.) is a tropical and sub-tropical, vegetative-propagated crop that contributes to approximately 80% of the sugar and 40% of the world's biofuel production. Modern sugarcane cultivars are highly polyploid and aneuploid hybrids with extremely large genomes (>10 Gigabases), that have originated from artificial crosses between the two species, Saccharum officinarum and S. spontaneum. The genetic complexity and low fertility of sugarcane under natural growing conditions make traditional breeding improvement extremely laborious, costly and time-consuming. This, together with its vegetative propagation, which allows for stable transfer and multiplication of transgenes, make sugarcane a good candidate for crop improvement through genetic engineering. Genetic transformation has the potential to improve economically important properties in sugarcane as well as diversify sugarcane beyond traditional applications, such as sucrose production. Traits such as herbicide, disease and insect resistance, improved tolerance to cold, salt and drought and accumulation of sugar and biomass have been some of the areas of interest as far as the application of transgenic sugarcane is concerned. Although there have been much interest in developing transgenic sugarcane there are only three officially approved varieties for commercialization, all of them expressing insect-resistance and recently released in Brazil. Since the early 1990's, different genetic transformation systems have been successfully developed in sugarcane, including electroporation, Agrobacterium tumefaciens and biobalistics. However, genetic transformation of sugarcane is a very laborious process, which relies heavily on intensive and sophisticated tissue culture and plant generation procedures that must be optimized for each new genotype to be transformed. Therefore, it remains a great technical challenge to develop an efficient transformation protocol for any sugarcane variety that has not been previously transformed. Additionally, once a transgenic event is obtained, molecular studies required for a commercial release by regulatory authorities, which include transgene insertion site, number of transgenes and gene expression levels, are all hindered by the genomic complexity and the lack of a complete sequenced reference genome for this crop. The objective of this review is to summarize current techniques and state of the art in sugarcane transformation and provide information on existing and future sugarcane improvement by genetic engineering.

Applying Molecular Phenotyping Tools to Explore Sugarcane Carbon Potential

Sugarcane (Saccharum spp.), a C₄ grass, has a peculiar feature: it accumulates, gradient-wise, large amounts of carbon (C) as sucrose in its culms through a complex pathway. Apart from being a sustainable crop concerning C efficiency and bioenergetic yield per hectare, sugarcane is used as feedstock for producing ethanol, sugar, high-value compounds, and products (e.g., polymers and succinate), and bioelectricity, earning the title of the world's leading biomass crop. Commercial cultivars, hybrids bearing high levels of polyploidy, and aneuploidy, are selected from a large number of crosses among suitable parental genotypes followed by the cloning of superior individuals among the progeny. Traditionally, these classical breeding strategies have been favoring the selection of cultivars with high sucrose content and resistance to environmental stresses. A current paradigm change in sugarcane breeding programs aims to alter the balance of C partitioning as a means to provide more plasticity in the sustainable use of this biomass for metabolic engineering and green chemistry. The recently available sugarcane genetic assemblies powered by data science provide exciting perspectives to increase biomass, as the current sugarcane yield is roughly 20% of its predicted potential. Nowadays, several molecular phenotyping tools can be applied to meet the predicted sugarcane C potential, mainly targeting two competing pathways: sucrose production/storage and biomass accumulation. Here we discuss how molecular phenotyping can be a powerful tool to assist breeding programs and which strategies could be adopted depending on the desired final products. We also tackle the advances in genetic markers and mapping as well as how functional genomics and genetic transformation might be able to improve yield and saccharification rates. Finally, we review how "omics" advances are promising to speed up plant breeding and reach the unexplored potential of sugarcane in terms of sucrose and biomass production.

Glyphosate: Uses Other Than in Glyphosate-Resistant Crops, Mode of Action, Degradation in Plants, and Effects on Non-target Plants and Agricultural Microbes

Glyphosate is the most used herbicide globally. It is a unique non-selective herbicide with a mode of action that is ideal for vegetation management in both agricultural and non-agricultural settings. Its use was more than doubled by the introduction of transgenic, glyphosate-resistant (GR) crops. All of its phytotoxic effects are the result of inhibition of only 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), but inhibition of this single enzyme of the shikimate pathway results in multiple phytotoxicity effects, both upstream and downstream from EPSPS, including loss of plant defenses against pathogens. Degradation of glyphosate in plants and microbes is predominantly by a glyphosate oxidoreductase to produce aminomethylphosphonic acid and glyoxylate and to a lesser extent by a C-P lyase to produce sarcosine and phosphate. Its effects on non-target plant species are generally less than that of many other herbicides, as it is not volatile and is generally sprayed in larger droplet sizes with a relatively low propensity to drift and is inactivated by tight binding to most soils. Some microbes, including fungal plant pathogens, have glyphosate-sensitive EPSPS. Thus, glyphosate can benefit GR crops by its activity on some plant pathogens. On the other hand, glyphosate can adversely affect some microbes that are beneficial to agriculture, such as Bradyrhizobium species, although GR crop yield data indicate that such an effect has been minor. Effects of glyphosate on microbes of agricultural soils are generally minor and transient, with other agricultural practices having much stronger effects.

Molecular and Toxicity Analyses of White Granulated Sugar and Other Processing Products Derived From Transgenic Sugarcane

This study aimed to prepare the sugar industry for the possible introduction of genetically modified (GM) sugarcane and derived retail sugar products and to address several potential public concerns regarding the characteristics and safety of these products. GM sugarcane lines with integrated Cry1Ab and EPSPS foreign genes were used for GM sugar production. Traditional PCR, real-time fluorescent quantitative PCR (RT-qPCR), and enzyme-linked immunosorbent assay (ELISA) were performed in analyzing leaves, stems, and other derived materials during sugar production, such as fibers, clarified juices, filter mud, syrups, molasses, and final GM sugar product. The toxicity of GM sugar was examined with a feeding bioassay using Helicoverpa armigera larvae. PCR and RT-qPCR results showed that the leaves, stems, fibers, juices, syrups, filter mud, molasses, and white granulated sugar from GM sugarcane can be distinguished from those derived from non-GM sugarcane. The RT-qPCR detection method using short amplified product primers was more accurate than the traditional PCR method. Molecular analysis results indicated that trace amounts of DNA residues remain in GM sugar, and thus it can be accurately characterized using molecular analysis methods. ELISA results showed that only the leaves, stems, fibers, and juices sampled from the GM sugarcane differed from those derived from the non-GM sugarcane, indicating that filter mud, syrup, molasses, and white sugar did not contain detectable Cry1Ab and EPSPS proteins. Toxicity analysis showed that the GM sugar was not toxic to the H. armigera larvae. The final results showed that the GM sugar had no active proteins despite containing trace amounts of DNA residues. This finding will help to pave the way for the commercialization of GM sugarcane and production of GM sugar.

Assessment of Gene Flow to Wild Relatives and Nutritional Composition of Sugarcane in Brazil

The commercial release of genetically modified organisms (GMO) requires a prior environmental and human/animal health risk assessment. In Brazil, the National Biotechnology Technical Commission (CTNBio) requires a survey of the area of natural occurrence of wild relatives of the GMO in the Brazilian ecosystems to evaluate the possibility of introgressive hybridization between sexually compatible species. Modern sugarcane cultivars, the focus of this study, derive from a series of hybridization and backcrossing events among Saccharum species. The so-called "Saccharum broad sense" group includes around 40 species from a few genera, including Erianthus, found in various tropical regions, particularly South-Eastern Asia. In Brazil, three native species, originally considered to belong to Erianthus, were reclassified as S. angustifolium (Nees) Trin., S. asperum (Nees) Steud., and S. villosum Steud., based on inflorescence morphology. Thus, we have investigated the potential occurrence of gene flow among the Brazilian Saccharum native species and commercial hybrids as a requisite for GMO commercial release. A comprehensive survey was carried out to map the occurrence of the three native Saccharum species in Brazil, concluding that they are sympatric with sugarcane cultivation only from around 14°S southwards, which precludes most Northeastern sugarcane-producing states from undergoing introgression. Based on phenology, we concluded that the Brazilian Saccharum species are unable to outcross naturally with commercial sugarcane since the overlap between the flowering periods of sugarcane and the native species is limited. A phylogenomic reconstruction based on the full plastid genome sequence showed that the three native Saccharum species are the taxa closest to sugarcane in Brazil, being closer than introduced Erianthus or Miscanthus. A 2-year study on eight nutritional composition traits of the 20 main sugarcane cultivars cultivated in Brazil was carried out in six environments. The minimum and maximum values obtained were, in percent: moisture (62.6-82.5); sucrose (9.65-21.76); crude fiber (8.06-21.03); FDN (7.20-20.68); FDA (4.55-16.90); lipids (0.06-1.59); ash (0.08-2.67); and crude protein (0.18-1.18). Besides a considerable amount of genetic variation and plastic responses, many instances of genotype-by-environment interaction were detected.

Inheritance and expression of Bt cry1Ba3 gene in progeny from transformed cabbage plants

Stable inheritance and expression of transgene are important parameters for successful use of a transgenic crop. We previously transformed a Bt cry1Ba3 gene into cabbage inbred line CA21-3. To evaluate the stability of our Bt cabbage lineages, transgene inheritance and expression were examined in four successive generations under greenhouse conditions. In our study, T₁, T₂ and T₃ progenies of the three independent transgenic lineages (YA-1, YA-2 and YA-3) were generated and then the inheritance and expression of cry1Ba3 were analyzed in sexually derived progeny. Segregation ratio of 2.81:1, 3.27:1 and 3.07:1 was found in T₁ progeny of lineages YA-1, YA-2 and YA-3, respectively. Chi-square analysis indicated that these segregation ratios of corresponding population fit the 3:1 ratio. Segregation ratios of the transgene in T₂ progeny showed either 3:1 or all expression of cry1Ba3. These data suggest that cry1Ba3 in CA21-3 can be inherited in a Mendelian manner. ELISA analysis of transgenic plants from four generations demonstrated that cry1Ba3 had been stably transmitted to the T₃ progeny. Additionally, under artificial infestation conditions, the homozygous T₃-YA-1-2-1 line exhibited excellent resistance to Plutella xylostella as compared with un-transformed CA21-3. All these results imply that the three cabbage lineages are genetically stable and can be used to inhibit damage on cabbage caused by P. xylostella.

Insights obtained using different modules of the cotton uceA1.7 promoter

The structure of the cotton uceA1.7 promoter and its modules was analyzed; the potential of their key sequences has been confirmed in different tissues, proving to be a good candidate for the development of new biotechnological tools. Transcriptional promoters are among the primary genetic engineering elements used to control genes of interest (GOIs) associated with agronomic traits. Cotton uceA1.7 was previously characterized as a constitutive promoter with activity higher than that of the constitutive promoter from the Cauliflower mosaic virus (CaMV) 35S gene in various plant tissues. In this study, we generated Arabidopsis thaliana homozygous events stably overexpressing the gfp reporter gene driven by different modules of the uceA1.7 promoter. The expression level of the reporter gene in different plant tissues and the transcriptional stability of these modules was determined compared to its full-length promoter and the 35S promoter. The full-length uceA1.7 promoter exhibited higher activity in different plant tissues compared to the 35S promoter. Two modules of the promoter produced a low and unstable transcription level compared to the other promoters. The other two modules rich in cis-regulatory elements showed similar activity levels to full-length uceA1.7 and 35S promoters but were less stable. This result suggests the location of a minimal portion of the promoter that is required to initiate transcription properly (the core promoter). Additionally, the full-length uceA1.7 promoter containing the 5'-untranslated region (UTR) is essential for higher transcriptional stability in various plant tissues. These findings confirm the potential use of the full-length uceA1.7 promoter for the development of new biotechnological tools (NBTs) to achieve higher expression levels of GOIs in, for example, the root or flower bud for the efficient control of phytonematodes and pest-insects, respectively, in important crops.

Foreign cry1Ac gene integration and endogenous borer stress-related genes synergistically improve insect resistance in sugarcane

BACKGROUND

Sugarcane (Saccharum spp. hybrids) is considered the most globally important sugar-producing crop and raw material for biofuel. Insect attack is a major issue in sugarcane cultivation, resulting in yield losses and sucrose content reductions. Stem borer (Diatraea saccharalis F.) causes serious yield losses in sugarcane worldwide. However, insect-resistant germplasms for sugarcane are not available in any collections all over the world, and the molecular mechanism of insect resistance has not been elucidated. In this study, cry1Ac transgenic sugarcane lines were obtained and the biological characteristics and transgene dosage effect were investigated and a global exploration of gene expression by transcriptome analysis was performed.

RESULTS

The transgene copies of foreign cry1Ac were variable and random. The correlation between the cry1Ac protein and cry1Ac gene copies differed between the transgenic lines from FN15 and ROC22. The medium copy lines from FN15 showed a significant linear relationship, while ROC22 showed no definite dosage effect. The transgenic lines with medium copies of cry1Ac showed an elite phenotype. Transcriptome analysis by RNA sequencing indicated that up/down regulated differentially expressed genes were abundant among the cry1Ac sugarcane lines and the receptor variety. Foreign cry1Ac gene and endogenous borer stress-related genes may have a synergistic effect. Three lines, namely, A1, A5, and A6, were selected for their excellent stem borer resistance and phenotypic traits and are expected to be used directly as cultivars or crossing parents for sugarcane borer resistance breeding.

CONCLUSIONS

Cry1Ac gene integration dramatically improved sugarcane insect resistance. The elite transgenic offspring contained medium transgene copies. Foreign cry1Ac gene integration and endogenous borer stress-related genes may have a synergistic effect on sugarcane insect resistance improvement.

Particle Bombardment of the cry2A Gene Cassette Induces Stem Borer Resistance in Sugarcane

Sugarcane borer is the most common and harmful pest in Chinese sugarcane fields, and can cause damage to the whole plant during the entire growing season. To improve borer resistance in sugarcane, we constructed a plant expression vector pGcry2A0229 with the bar gene as the marker and the cry2A gene as the target, and introduced it into embryogenic calli of most widely cultivated sugarcane cultivar ROC22 by particle bombardment. After screening with phosphinothricin in vitro and Basta spray, 21 resistance-regenerated plants were obtained, and 10 positive transgenic lines harboring the cry2A gene were further confirmed by conventional PCR detection. Real-time quantitative PCR (RT-qPCR) analysis showed that the copy number of the cry2A gene varied among different transgenic lines but did not exceed four copies. Quantitative ELISA analysis showed that there was no linear relationship with copy number but negatively correlated with the percentage of borer-infested plants. The analysis of industrial and agronomic traits showed that the theoretical sugar yields of transgenic lines TR-4 and TR-10 were slightly lower than that of the control in both plant cane and ratoon cane; nevertheless, TR-4 and TR-10 lines exhibited markedly lower in frequency of borer-infested plants in plant cane and in the ratoon cane compared to the control. Our results indicate that the introduction of the cry2A gene via bombardment produces transgenic lines with obviously increased stem borer resistance and comparable sugar yield, providing a practical value in direct commercial cultivation and crossbreeding for ROC22 has been used as the most popular elite genitor in various breeding programs in China.