Stable and Efficient Agrobacterium-Mediated Genetic Transformation of Larch Using Embryogenic Callus

RNAi-mediated downregulation of endogenous 4-coumarate: CoA ligase activity in Sorghum bicolor to alter the lignin content, which augmented the carbohydrate content and growth

MAIN CONCLUSION

This study seeks to improve the biomass extractability of Sorghum bicolor by targeting a critical enzyme, 4CL, through metabolic engineering of the lignin biosynthetic pathway at the post-transcriptional level. Sorghum bicolor L., a significant forage crop, offers a potential source of carbohydrate components for biofuel production. The high lignin content in sorghum stems often impedes the extractability of desired carbohydrate components for industrial use. Thus, the present study aimed to develop an improved variety of S. bicolor with reduced lignin through RNA interference of the endogenous 4-coumarate:CoA ligase (4CL) gene involved in the lignin biosynthetic pathway. The S. bicolor gene was isolated, characterized, and used to construct the RNAi-inducing hpRNA gene-silencing construct. Two independent transgenic sorghum lines were produced by introducing an hpRNA-induced gene-silencing cassette of the Sb4CL through Agrobacterium-mediated transformation in the shoot tips of S. bicolor. This was confirmed by PCR amplification of the hygromycin-resistance gene and Southern hybridization. The Sb4CL gene transcript and its enzymatic activity were found to reduce to varying degrees, as shown by northern hybridization and enzyme activity in the independent transgenic samples. Endogenous Sb4CL downregulation in sorghum stem tissue correlates with reduced lignin content to a maximum range of 25%. The transfer of the transgene in the second generation was also analyzed. Decreased lignin content in the transgenic lines was compensated by increased total cell wall carbohydrates such as cellulose (36.56%) and soluble sugars (59.72%) compared to untransformed plants. The study suggests that suppressing the Sb4CL gene effectively develops better sorghum varieties with lower lignin content. This can be useful for industrial purposes, as the enhanced carbohydrate content and favorable alteration of lignin content can lead to economic benefits.

Simple and Fail-safe Method to Transform Miniprep Escherichia coli Strain K12 Plasmid DNA Into Viable Agrobacterium tumefaciens EHA105 Cells for Plant Genetic Transformation

Agrobacterium-mediated gene transformation method is a vital molecular biology technique employed to develop transgenic plants. Plants are genetically engineered to develop disease-free varieties, knock out unsettling traits for crop improvement, or incorporate an antigenic protein to make the plant a green factory for edible vaccines. The method's robustness was validated through successful transformations, demonstrating its effectiveness as a standard approach for researchers working in plant biotechnology. It enables the introduction of foreign DNA into plant genomes. Conventionally, plant genetic transformation has relied on time-consuming, costly, and technically demanding procedures, such as electroporation and chimeric viruses or biolistic methods, which usually yield variable transformation efficiencies. This study presents a simple and fail-safe protocol that involves a modified freeze-thaw and heat-shock concoction method. This approach involves a streamlined plasmid miniprep procedure to isolate high-quality plasmid DNA from Escherichia coli K12 strain, followed by a target-specific transfer into A. tumefaciens EHA105 strain. The optimized method minimizes DNA degradation and maximizes uptake by Agrobacterium cells, making it a reproducible and accessible protocol for various genetic engineering applications. The transformation efficiency is consistently high, enhancing plasmid uptake while maintaining cell viability, requiring minimal specialized equipment and reagents. The proposed protocol offers significant advantages, including simplicity, reliability, and cost-effectiveness, positioning it as a valuable alternative to traditional techniques in the field of plant biotechnology. Key features • Uses liquid nitrogen as a proxy for freezing. • Plasmid DNA from competent bacterial cells is extracted using a user-friendly high-copy isolation kit. • A maximum of five consecutive days is sufficient to complete the procedures.

Construction and Validation of CRISPR/Cas Vectors for Editing the PDS Gene in Banana (Musa spp.)

Bananas and plantains are important staple food crops affected by biotic and abiotic stresses. The gene editing technique via Clustered Regularly Interspaced Short Palindromic Repeats associated with the Cas protein (CRISPR/Cas) has been used as an important tool for development of cultivars with high tolerance to stresses. This study sought to develop a protocol for the construction of vectors for gene knockout. Here we use the phytoene desaturase (PDS) gene as a case study in Prata-Anã banana by the nonhomologous end junction (NHEJ) method. PDS is a key gene in the carotenoid production pathway in plants and its knockout leads to easily visualized phenotypes such as dwarfism and albinism in plants. Agrobacterium-mediated transformation delivered CRISPR/Cas9 constructs containing gRNAs were inserted into embryogenic cell suspension cultures. This is the first study to provide an effective method/protocol for constructing gene knockout vectors, demonstrating gene editing potential in a Brazilian banana variety. The constitutive (CaMV 35S) and root-specific vectors were successfully assembled and confirmed in transformed Agrobacterium by DNA extraction and PCR. The specificity of transformation protocols makes it possible to use the CRISPR-Cas9 technique to develop Prata-Anã banana plants with enhanced tolerance/resistance to major biotic and abiotic factors.

Screening and Functional Evaluation of Four Larix kaempferi Promoters

Promoters are powerful tools for breeding new varieties using transgenic technology. However, the low and unstable expression of target genes is still a limiting factor in Larix kaempferi (Lamb.) Carr (Japanese larch) genetic transformation. In this study, we analyzed L. kaempferi transcriptome data, screened out highly expressed genes, cloned their promoters, and constructed plant expression vectors containing the β-glucuronidase (GUS) reporter gene driven by these promoters. Recombinant vectors were introduced into the L. kaempferi embryogenic callus by means of the Agrobacterium-mediated transient or stable genetic transformation method, and the promoter activity was then determined by measuring GUS expression and its enzyme activity in the transformed materials. Four highly expressed genes were identified: L. kaempferi Zhang Chen Yi-1 (LaZCY-1), Zhang Chen Yi-2 (LaZCY-2), Translationally Controlled Tumor Protein (LaTCTP), and ubiquitin (LaUBQ). The 2000 bp fragments upstream of ATG in these sequences were cloned as promoters and named pLaZCY-1, pLaZCY-2, pLaTCTP, and pLaUBQ. Semi-quantitative and quantitative RT-PCR analyses of transient genetic transformation materials showed that all four promoters could drive GUS expression, indicating that they have promoter activities. Semi-quantitative and quantitative RT-PCR analyses and the histochemical staining of stable genetic transformation materials showed that the pLaUBQ promoter had higher activity than the other three L. kaempferi promoters and the CaMV35S promoter. Thus, the pLaUBQ promoter was suggested to be used in larch genetic transformation.

Genetic transformation in conifers: current status and future prospects

Genetic transformation has been a cornerstone in plant molecular biology research and molecular design breeding, facilitating innovative approaches for the genetic improvement of trees with long breeding cycles. Despite the profound ecological and economic significance of conifers in global forestry, the application of genetic transformation in this group has been fraught with challenges. Nevertheless, genetic transformation has achieved notable advances in certain conifer species, while these advances are confined to specific genotypes, they offer valuable insights for technological breakthroughs in other species. This review offers an in-depth examination of the progress achieved in the genetic transformation of conifers. This discussion encompasses various factors, including expression vector construction, gene-delivery methods, and regeneration systems. Additionally, the hurdles encountered in the pursuit of a universal model for conifer transformation are discussed, along with the proposal of potential strategies for future developments. This comprehensive overview seeks to stimulate further research and innovation in this crucial field of forest biotechnology.

The establishment of transient expression systems and their application for gene function analysis of flavonoid biosynthesis in Carthamus tinctorius L

BACKGROUND

Safflower (Carthamus tinctorius L.) is an important economic crop and a traditional medicinal material rich in flavonoids, which can alleviate cardiovascular and cerebrovascular pathologies. Thus, many candidate genes involved in safflower flavonoid biosynthesis have been cloned. However, owing to the lack of a homologous gene expression system, research on gene function is limited to model plants. Therefore, a gene function identification protocol for safflower must be established.

RESULTS

In the present study, using safflower callus as the experimental material, Agrobacterium and biolistic transient expression systems were established. In the Agrobacterium transient expression system, the highest transformation rate was obtained at the original Agrobacterium concentration of OD600 0.4, infiltration concentration of OD600 0.6, infection for 20 min, co-culture for 3 days, and acetosyringone concentration of 100 μmol·L-1. In the biolistic transient expression system, the highest transformation efficiency was observed at helium pressure of 1,350 psi, vacuum degree of -0.8 bar, flight distance of 6.5 cm, one round of bombardment, plasmid concentration of 3 μg·shot-1, and gold particle concentration of 100 μg·shot-1. Further, these two transient expression systems were used for the functional analysis of CtCHS1 as an example. After overexpression, relative CtCHS1 expression increased, particularly in Agrobacterium-transformed calli. Additionally, the contents of some flavonoids were altered; for instance, naringenin and genistein levels were significantly increased in Agrobacterium-transformed calli, whereas luteolin, luteolin-7-O-rutinoside, and apigenin derivative levels were significantly decreased in biolistic-transformed calli.

CONCLUSION

Using safflower callus as the experimental material, highly efficient Agrobacterium and biolistic transient expression systems were successfully established, and the utility of both systems for investigating gene function was demonstrated. The proposed safflower callus transient expression systems will be useful for further functional analyses of flavonoid biosynthetic genes in safflower.

Application of a novel strong promoter from Chinese fir (Cunninghamia lanceolate) in the CRISPR/Cas mediated genome editing of its protoplasts and transgenesis of rice and poplar

Novel constitutive promoters are essential for plant biotechnology. Although in angiosperms, a number of promoters were applied in monocots or dicots genetic engineering, only a few promoters were used in gymnosperm. Here we identified two strong promoters (Cula11 and Cula08) from Chinese fir (C. lanceolate) by screening the transcriptomic data and preliminary promoter activity assays in tobacco. By using the newly established Chinese fir protoplast transient expression technology that enables in vivo molecular biology studies in its homologous system, we compared the activities of Cula11 and Cula08 with that of the commonly used promoters in genetic engineering of monocots or dicots, such as CaM35S, CmYLCV, and ZmUbi, and our results revealed that Cula11 and Cula08 promoters have stronger activities in Chinese fir protoplasts. Furthermore, the vector containing Cas gene driven by Cula11 promoter and sgRNA driven by the newly isolated CulaU6b polyIII promoters were introduced into Chinese fir protoplasts, and CRISPR/Cas mediated gene knock-out event was successfully achieved. More importantly, compared with the commonly used promoters in the genetic engineering in angiosperms, Cula11 promoter has much stronger activity than CaM35S promoter in transgenic poplar, and ZmUbi promoter in transgenic rice, respectively, indicating its potential application in poplar and rice genetic engineering. Overall, the novel putative constitutive gene promoters reported here will have great potential application in gymnosperm and angiosperm biotechnology, and the transient gene expression system established here will serve as a useful tool for the molecular and genetic analyses of Chinese fir genes.