Evolution of CRISPR/Cas Systems for Precise Genome Editing

CRISPR-Cas Systems and Genome Editing: Beginning the Era of CRISPR/Cas Therapies for Humans

Harnessing of CRISPR/Cas (Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR-associated genes) systems for detection, chemical modification, and sequence editing of nucleic acids dramatically changed many fields of fundamental science, biotechnology, and biomedicine [...].

Advances in application of CRISPR-Cas13a system

Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs) and CRISPR-associated (Cas) proteins serve as an adaptive immune system that safeguards prokaryotes and some of the viruses that infect prokaryotes from foreign nucleic acids (such as viruses and plasmids). The genomes of the majority of archaea and about half of all bacteria contain various CRISPR-Cas systems. CRISPR-Cas systems depend on CRISPR RNAs (crRNAs). They act as a navigation system to specifically cut and destroy foreign nucleic acids by recognizing invading foreign nucleic acids and binding Cas proteins. In this review, we provide a brief overview of the evolution and classification of the CRISPR-Cas system, focusing on the functions and applications of the CRISPR-Cas13a system. We describe the CRISPR-Cas13a system and discuss its RNA-directed ribonuclease function. Meanwhile, we briefly introduce the mechanism of action of the CRISPR-Cas13a system and summarize the applications of the CRISPR-Cas13a system in pathogen detection, eukaryotes, agriculture, biosensors, and human gene therapy. We are right understanding of CRISPR-Cas13a has been broadened, and the CRISPR-Cas13a system will be useful for developing new RNA targeting tools. Therefore, understanding the basic details of the structure, function, and biological characterization of CRISPR-Cas13a effector proteins is critical for optimizing RNA targeting tools.

Genetic improvement in edible fish: status, constraints, and prospects on CRISPR-based genome engineering

Conventional selective breeding in aquaculture has been effective in genetically enhancing economic traits like growth and disease resistance. However, its advances are restricted by heritability, the extended period required to produce a strain with desirable traits, and the necessity to target multiple characteristics simultaneously in the breeding programs. Genome editing tools like zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 (CRISPR/Cas9) are promising for faster genetic improvement in fishes. CRISPR/Cas9 technology is the least expensive, most precise, and well compatible with multiplexing of all genome editing approaches, making it a productive and highly targeted approach for developing customized fish strains with specified characteristics. As a result, the use of CRISPR/Cas9 technology in aquaculture is rapidly growing, with the main traits researched being reproduction and development, growth, pigmentation, disease resistance, trans-GFP utilization, and omega-3 metabolism. However, technological obstacles, such as off-target effects, ancestral genome duplication, and mosaicism in founder population, need to be addressed to achieve sustainable fish production. Furthermore, present regulatory and risk assessment frameworks are inadequate to address the technical hurdles of CRISPR/Cas9, even though public and regulatory approval is critical to commercializing novel technology products. In this review, we examine the potential of CRISPR/Cas9 technology for the genetic improvement of edible fish, the technical, ethical, and socio-economic challenges to using it in fish species, and its future scope for sustainable fish production.

CRISPR-based resistance to grapevine virus A

Introduction

Grapevine (Vitis vinifera) is an important fruit crop which contributes significantly to the agricultural sector worldwide. Grapevine viruses are widespread and cause serious diseases which impact the quality and quantity of crop yields. More than 80 viruses plague grapevine, with RNA viruses constituting the largest of these. A recent extension to the clustered regularly interspaced, short palindromic repeat (CRISPR) armory is the Cas13 effector, which exclusively targets single-strand RNA. CRISPR/Cas has been implemented as a defense mechanism in plants, against both DNA and RNA viruses, by being programmed to directly target and cleave the viral genomes. The efficacy of the CRISPR/Cas tool in plants is dependent on efficient delivery of its components into plant cells.

Methods

To this end, the aim of this study was to use the recent Cas13d variant from Ruminococcus flavefaciens (CasRx) to target the RNA virus, grapevine virus A (GVA). GVA naturally infects grapevine, but can infect the model plant Nicotiana benthamiana, making it a helpful model to study virus infection in grapevine. gRNAs were designed against the coat protein (CP) gene of GVA. N. benthamiana plants expressing CasRx were co-infiltrated with GVA, and with a tobacco rattle virus (TRV)-gRNA expression vector, harbouring a CP gRNA.

Results and discussion

Results indicated more consistent GVA reductions, specifically gRNA CP-T2, which demonstrated a significant negative correlation with GVA accumulation, as well as multiple gRNA co-infiltrations which similarly showed reduced GVA titre. By establishing a virus-targeting defense system in plants, efficient virus interference mechanisms can be established and applied to major crops, such as grapevine.