Advance of Clustered Regularly Interspaced Short Palindromic Repeats-Cas9 System and Its Application in Crop Improvement

Genome editing in Sub-Saharan Africa: a game-changing strategy for climate change mitigation and sustainable agriculture

Sub-Saharan Africa's agricultural sector faces a multifaceted challenge due to climate change consisting of high temperatures, changing precipitation trends, alongside intensified pest and disease outbreaks. Conventional plant breeding methods have historically contributed to yield gains in Africa, and the intensifying demand for food security outpaces these improvements due to a confluence of factors, including rising urbanization, improved living standards, and population growth. To address escalating food demands amidst urbanization, rising living standards, and population growth, a paradigm shift toward more sustainable and innovative crop improvement strategies is imperative. Genome editing technologies offer a promising avenue for achieving sustained yield increases while bolstering resilience against escalating biotic and abiotic stresses associated with climate change. Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR-associated protein (CRISPR/Cas) is unique due to its ubiquity, efficacy, alongside precision, making it a pivotal tool for Sub-Saharan African crop improvement. This review highlights the challenges and explores the prospect of gene editing to secure the region's future foods.

Identification, charectrization and genetic transformation of lignin and pectin polysaccharides through CRISPR/Cas9 in Nicotiana tobacum

CRISPR/Cas9 system has been successfully implemented in animals and plants is a second-generation genome editing tool. We are able to optimize a Cas9 system to edited Ntab06050 and Ntab0857410 genes in HD and K326 tobacco cultivars respectively. The gene Ntab06050 is related to lignin synthesis while the gene Ntab0857410 belongs to pectin synthesis by utilizing Agrobacterium-mediated leaf disc method. We have constructed total eight different constructs for the lignin related gene family CCoAMT, out of which three constructs have been selected from Ntab0184090, two constructs from Ntab0392460 while one construct from each Ntab0540120, Ntab0857410 and Ntab0135940 gene. To study the Cas9 system in pectin related genes, total five constructs have been utilized under Cas9 system and multiple target sites were selected by identifying PAM sequences. Out of which three constructs were targeted from NtabGAE1and NtabGAE6 homologous while two were targeted from NtabGAUT4 homologous. Where as, UDP-D-glucuronate 4-epimerase gene family is a Golgi localized, might have a role in the interconvertion of UDP-D-GlcA and UDP-D-GalA in pectin synthesis. We have succeeded in the mutation of pectin related NtabGAUT4 and lignin related NtabCCoAMT genes with 6.2% and 9.4% mutation frequency.

Targeted genome-modification tools and their advanced applications in crop breeding

Crop improvement by genome editing involves the targeted alteration of genes to improve plant traits, such as stress tolerance, disease resistance or nutritional content. Techniques for the targeted modification of genomes have evolved from generating random mutations to precise base substitutions, followed by insertions, substitutions and deletions of small DNA fragments, and are finally starting to achieve precision manipulation of large DNA segments. Recent developments in base editing, prime editing and other CRISPR-associated systems have laid a solid technological foundation to enable plant basic research and precise molecular breeding. In this Review, we systematically outline the technological principles underlying precise and targeted genome-modification methods. We also review methods for the delivery of genome-editing reagents in plants and outline emerging crop-breeding strategies based on targeted genome modification. Finally, we consider potential future developments in precise genome-editing technologies, delivery methods and crop-breeding approaches, as well as regulatory policies for genome-editing products.

Advances in CRISPR/Cas9-based research related to soybean [Glycine max (Linn.) Merr] molecular breeding

Soybean [Glycine max (Linn.) Merr] is a source of plant-based proteins and an essential oilseed crop and industrial raw material. The increase in the demand for soybeans due to societal changes has coincided with the increase in the breeding of soybean varieties with enhanced traits. Earlier gene editing technologies involved zinc finger nucleases and transcription activator-like effector nucleases, but the third-generation gene editing technology uses clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9). The rapid development of CRISPR/Cas9 technology has made it one of the most effective, straightforward, affordable, and user-friendly technologies for targeted gene editing. This review summarizes the application of CRISPR/Cas9 technology in soybean molecular breeding. More specifically, it provides an overview of the genes that have been targeted, the type of editing that occurs, the mechanism of action, and the efficiency of gene editing. Furthermore, suggestions for enhancing and accelerating the molecular breeding of novel soybean varieties with ideal traits (e.g., high yield, high quality, and durable disease resistance) are included.

The Potential of CRISPR/Cas Technology to Enhance Crop Performance on Adverse Soil Conditions

Worldwide food security is under threat in the actual scenery of global climate change because the major staple food crops are not adapted to hostile climatic and soil conditions. Significant efforts have been performed to maintain the actual yield of crops, using traditional breeding and innovative molecular techniques to assist them. However, additional strategies are necessary to achieve the future food demand. Clustered regularly interspaced short palindromic repeat/CRISPR-associated protein (CRISPR/Cas) technology, as well as its variants, have emerged as alternatives to transgenic plant breeding. This novelty has helped to accelerate the necessary modifications in major crops to confront the impact of abiotic stress on agriculture systems. This review summarizes the current advances in CRISPR/Cas applications in crops to deal with the main hostile soil conditions, such as drought, flooding and waterlogging, salinity, heavy metals, and nutrient deficiencies. In addition, the potential of extremophytes as a reservoir of new molecular mechanisms for abiotic stress tolerance, as well as their orthologue identification and edition in crops, is shown. Moreover, the future challenges and prospects related to CRISPR/Cas technology issues, legal regulations, and customer acceptance will be discussed.

Strategies and Methods for Improving the Efficiency of CRISPR/Cas9 Gene Editing in Plant Molecular Breeding

Following recent developments and refinement, CRISPR-Cas9 gene-editing technology has become increasingly mature and is being widely used for crop improvement. The application of CRISPR/Cas9 enables the generation of transgene-free genome-edited plants in a short period and has the advantages of simplicity, high efficiency, high specificity, and low production costs, which greatly facilitate the study of gene functions. In plant molecular breeding, the gene-editing efficiency of the CRISPR-Cas9 system has proven to be a key step in influencing the effectiveness of molecular breeding, with improvements in gene-editing efficiency recently becoming a focus of reported scientific research. This review details strategies and methods for improving the efficiency of CRISPR/Cas9 gene editing in plant molecular breeding, including Cas9 variant enzyme engineering, the effect of multiple promoter driven Cas9, and gRNA efficient optimization and expression strategies. It also briefly introduces the optimization strategies of the CRISPR/Cas12a system and the application of BE and PE precision editing. These strategies are beneficial for the further development and optimization of gene editing systems in the field of plant molecular breeding.

CRISPR-Cas technology opens a new era for the creation of novel maize germplasms

Maize (Zea mays) is one of the most important food crops in the world with the greatest global production, and contributes to satiating the demands for human food, animal feed, and biofuels. With population growth and deteriorating environment, efficient and innovative breeding strategies to develop maize varieties with high yield and stress resistance are urgently needed to augment global food security and sustainable agriculture. CRISPR-Cas-mediated genome-editing technology (clustered regularly interspaced short palindromic repeats (CRISPR)-Cas (CRISPR-associated)) has emerged as an effective and powerful tool for plant science and crop improvement, and is likely to accelerate crop breeding in ways dissimilar to crossbreeding and transgenic technologies. In this review, we summarize the current applications and prospects of CRISPR-Cas technology in maize gene-function studies and the generation of new germplasm for increased yield, specialty corns, plant architecture, stress response, haploid induction, and male sterility. Optimization of gene editing and genetic transformation systems for maize is also briefly reviewed. Lastly, the challenges and new opportunities that arise with the use of the CRISPR-Cas technology for maize genetic improvement are discussed.

Knockout of phytoene desaturase gene using CRISPR/Cas9 in highbush blueberry

Among the New Plant Breeding Techniques (NPBTs), the CRISPR/Cas9 system represents a useful tool for target gene editing, improving the traits of the plants rapidly. This technology allows targeting one or more sequences simultaneously, as well as introducing new genetic variations by homology-directed recombination. However, the technology of CRISPR/Cas9 remains a challenge for some polyploid woody species, since all the different alleles for which the mutation is required must be simultaneously targeted. In this work we describe improved protocols adapting the CRISPR/Cas9 system to highbush blueberry (Vaccinium corymbosum L.), using Agrobacterium-mediated transformation. As a proof of concept, we targeted the gene encoding for phytoene desaturase, whose mutation disrupts chlorophyll biosynthesis allowing for the visual assessment of knockout efficiency. Leaf explants of in vitro-cultured blueberry cv. Berkeley has been transformed with a CRISPR/Cas9 construct containing two guide RNAs (gRNA1 and gRNA2) targeting two conserved gene regions of pds and subsequently maintained on a selection medium enriched with kanamycin. After 4 weeks in culture on the selection medium, the kanamycin-resistant lines were isolated, and the genotyping of these lines through Sanger sequencing revealed successful gene editing. Some of mutant shoot lines included albino phenotypes, even if the editing efficiencies were quite low for both gRNAs, ranging between 2.1 and 9.6% for gRNA1 and 3.0 and 23.8 for gRNA2. Here we showed a very effective adventitious shoot regeneration protocol for the commercial cultivar of highbush blueberry "Berkeley", and a further improvement in the use of CRISPR/Cas9 system in Vaccinium corymbosum L., opening the way to the breeding mediated by biotechnological approaches.

CRISPR/Cas9 Technology and Its Utility for Crop Improvement

The rapid growth of the global population has resulted in a considerable increase in the demand for food crops. However, traditional crop breeding methods will not be able to satisfy the worldwide demand for food in the future. New gene-editing technologies, the most widely used of which is CRISPR/Cas9, may enable the rapid improvement of crop traits. Specifically, CRISPR/Cas9 genome-editing technology involves the use of a guide RNA and a Cas9 protein that can cleave the genome at specific loci. Due to its simplicity and efficiency, the CRISPR/Cas9 system has rapidly become the most widely used tool for editing animal and plant genomes. It is ideal for modifying the traits of many plants, including food crops, and for creating new germplasm materials. In this review, the development of the CRISPR/Cas9 system, the underlying mechanism, and examples of its use for editing genes in important crops are discussed. Furthermore, certain limitations of the CRISPR/Cas9 system and potential solutions are described. This article will provide researchers with important information regarding the use of CRISPR/Cas9 gene-editing technology for crop improvement, plant breeding, and gene functional analyses.

CRISPR-Cas9 Gene Editing of the Sal1 Gene Family in Wheat

The highly conserved Sal1 encodes a bifunctional enzyme with inositol polyphosphate-1-phosphatase and 3′ (2′), 5′-bisphosphate nucleotidase activity and has been shown to alter abiotic stress tolerance in plants when disrupted. Precise gene editing techniques were used to generate Sal1 mutants in hexaploid bread wheat. The CRISPR (Clustered Regulatory Interspaced Short Palindromic Repeats) Cas9 system with three guide RNAs (gRNAs) was used to inactivate six Sal1 homologous genes within the Bobwhite wheat genome. The resulting mutant wheat plants with all their Sal1 genes disabled had slimmer stems, had a modest reduction in biomass and senesced more slowly in water limiting conditions, but did not exhibit improved yield under drought conditions. Our results show that multiplexed gRNAs enabled effective targeted gene editing of the Sal1 gene family in hexaploid wheat. These Sal1 mutant wheat plants will be a resource for further research studying the function of this gene family in wheat.