140 research outputs found
Plant genome editing by CRISPRâCas systems
Since its first appearance, CRISPRâCas9 has been developed extensively as a programmable genome-editing tool, opening a new era in plant genome engineering. However, CRISPRâCas9 still has some drawbacks, such as limitations of the protospacer-adjacent motif (PAM) sequence, target specificity, and the large size of the cas9 gene. To combat invading bacterial phages and plasmid DNAs, bacteria and archaea have diverse and unexplored CRISPRâCas systems, which have the potential to be developed as a useful genome editing tools. Recently, discovery and characterization of additional CRISPRâCas systems have been reported. Among them, several CRISPRâCas systems have been applied successfully to plant and human genome editing. For example, several groups have achieved genome editing using CRISPRâCas type I-D and type I-E systems, which had never been applied for genome editing previously. In addition to higher specificity and recognition of different PAM sequences, recently developed CRISPRâCas systems often provide unique characteristics that differ from well-known Cas proteins such as Cas9 and Cas12a. For example, type I CRISPRâCas10 induces small indels and bi-directional long-range deletions ranging up to 7.2âkb in tomatoes (Solanum lycopersicum L.). Type IV CRISPRâCas13 targets RNA, not double-strand DNA, enabling highly specific knockdown of target genes. In this article, we review the development of CRISPRâCas systems, focusing especially on their application to plant genome engineering. Recent CRISPRâCas tools are helping expand our plant genome engineering toolbox
Genome engineering of woody plants : past, present and future
Engineered endonucleases that digest the specific sequences can be used to modify target genomes precisely. This is called âgenome editingâ and is used widely to modify the genome of various organisms. The DNA-binding domains of zinc finger (ZF) proteins were the first to be used as a genome editing tool, in the form of designed ZF nucleases and, more recently, transcription activator-like effector as well as the clustered, regularly interspaced, short palindromic repeats and CRISPR-associated protein 9 (CRISPR/Cas9) system that targets RNAâDNA rather than proteinâDNA interactions have been used successfully. These are powerful tools with which targeted gene modifications can be introduced in various organisms, including various plant species. A key step in genome editing is the generation of a double-stranded DNA break that is specific to the target gene. This is achieved using custom-designed endonucleases, which enable site-directed mutagenesis via a non-homologous end joining repair pathway and/or gene targeting via homologous recombination to occur efficiently at specific sites in the genome. This review provides an overview of the current status of genomics and genetic engineering of woody plants, and recent advances in genome editing technologies in plants as well as fungi. We also discuss how these strategies can provide insights into molecular breeding technology for woody plants
Precision genome editing in plants : state-of- the-art in CRISPR/Cas9-based genome engineering
Traditionally, generation of new plants with improved or desirable features has relied on laborious and time-consuming breeding techniques. Genome-editing technologies have led to a new era of genome engineering, enabling an effective, precise, and rapid engineering of the plant genomes. Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (CRISPR/Cas9) has emerged as a new genome-editing tool, extensively applied in various organisms, including plants. The use of CRISPR/Cas9 allows generating transgene-free genome-edited plants (ânull segregantsâ) in a short period of time. In this review, we provide a critical overview of the recent advances in CRISPR/Cas9 derived technologies for inducing mutations at target sites in the genome and controlling the expression of target genes. We highlight the major breakthroughs in applying CRISPR/Cas9 to plant engineering, and challenges toward the production of null segregants. We also provide an update on the efforts of engineering Cas9 proteins, newly discovered Cas9 variants, and novel CRISPR/Cas systems for use in plants. The application of CRISPR/Cas9 and related technologies in plant engineering will not only facilitate molecular breeding of crop plants but also accelerate progress in basic research
Multiplex Genome Editing in Tomato
Several expression systems for multiple guide RNA (gRNAs) have been developed in the CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/CRISPR associated protein 9) system to induce multiple-gene modifications in plants. Here, we evaluated mutation efficiencies in the tomato genome using multiplex CRISPR/Cas9 vectors consisting of various Cas9 expression promoters with multiple gRNA expression combinations. In transgenic tomato calli induced with these vectors, mutation patterns varied depending on the promoters used to express Cas9. By using the tomato ELONGATION FACTOR-1α (SlEF1α) promoter to drive Cas9, occurrence of various types of mutations with high efficiency was detected in the tomato genome. Furthermore, sequence analysis showed that the majority of mutations using the multiplex system with the SlEF1α promoter corresponded to specific mutation pattern of deletions produced by self-ligation at two target sites of CRISPR/Cas9 with low mosaic mutations. These results suggest that optimizing the Cas9 expression promoter used in CRISPR/Cas9-mediated mutation improves multiplex genome editing, and could be used effectively to disrupt functional domains precisely in the tomato genome
Genome editing in mammalian cells using the CRISPR type I-D nuclease
Adoption of CRISPRâCas systems, such as CRISPRâCas9 and CRISPRâCas12a, has revolutionized genome engineering in recent years; however, application of genome editing with CRISPR type Iâthe most abundant CRISPR system in bacteriaâremains less developed. Type I systems, such as type I-E, and I-F, comprise the CRISPR-associated complex for antiviral defense (âCascadeâ: Cas5, Cas6, Cas7, Cas8 and the small subunit) and Cas3, which degrades the target DNA; in contrast, for the sub-type CRISPRâCas type I-D, which lacks a typical Cas3 nuclease in its CRISPR locus, the mechanism of target DNA degradation remains unknown. Here, we found that Cas10d is a functional nuclease in the type I-D system, performing the role played by Cas3 in other CRISPRâCas type I systems. The type I-D system can be used for targeted mutagenesis of genomic DNA in human cells, directing both bi-directional long-range deletions and short insertions/deletions. Our findings suggest the CRISPRâCas type I-D system as a unique effector pathway in CRISPR that can be repurposed for genome engineering in eukaryotic cells
SlIAA9 Controls Tomato Elongation
Tomato INDOLE-3-ACETIC ACID9 (SlIAA9) is a transcriptional repressor in auxin signal transduction, and SlIAA9 knockout tomato plants develop parthenocarpic fruits without fertilization. We generated sliaa9 mutants with parthenocarpy in several commercial tomato cultivars (Moneymaker, Rio Grande, and Ailsa Craig) using CRISPR-Cas9, and null-segregant lines in the T1 generation were isolated by self-pollination, which was confirmed by PCR and Southern blot analysis. We then estimated shoot growth phenotypes of the mutant plants under different light (low and normal) conditions. The shoot length of sliaa9 plants in Moneymaker and Rio Grande was smaller than those of wild-type cultivars in low light conditions, whereas there was not clear difference between the mutant of Ailsa Craig and the wild-type under both light conditions. Furthermore, young seedlings in Rio Grande exhibited shade avoidance response in hypocotyl growth, in which the hypocotyl lengths were increased in low light conditions, and sliaa9 mutant seedlings of Ailsa Craig exhibited enhanced responses in this phenotype. Fruit production and growth rates were similar among the sliaa9 mutant tomato cultivars. These results suggest that control mechanisms involved in the interaction of AUX/IAA9 and lights condition in elongation growth differ among commercial tomato cultivars
A novel ER export signal of STP transporters
Membrane trafficking is highly organized to maintain cellular homeostasis in any organisms. Membrane-embedded transporters are targeted to various organelles to execute appropriate partition and allocation of their substrates, such as ions or sugars. To ensure the fidelity of targeting and sorting, membrane proteins including transporters have sorting signals that specify the subcellular destination and the trafficking pathway by which the destination is to be reached. Here, we have identified a novel sorting signal (called the tri-aromatic motif) which contains three aromatic residues, two tryptophans and one histidine, for the plasma membrane localization of sugar transporters in the STP family in Arabidopsis. We firstly found that a C-terminal deletion disrupted the sugar uptake activity of STP1 in yeast cells. Additional deletion and mutation analyses demonstrated that the three aromatic residues in the C-terminus, conserved among all Arabidopsis STP transporters, were critical for sugar uptake by not only STP1 but also another STP transporter STP13. We observed that, when the tri-aromatic motif was mutated, STP1 was largely localized at the endomembrane compartments in yeast cells, indicating that this improper subcellular localization led to the loss of sugar absorption. Importantly, our further analyses uncovered that mutations of the tri-aromatic motif resulted in the endoplasmic reticulum (ER) retention of STP1 and STP13 in plant cells, suggesting that this motif is involved at the step of ER exit of STP transporters to facilitate their plasma membrane localization. Together, we here identified a novel ER export signal, and showed that appropriate sorting via the tri-aromatic motif is important for sugar absorption by STP transporters
Direct conversion of carlactonoic acid to orobanchol by cytochrome P450 CYP722C in strigolactone biosynthesis
Strigolactones (SLs) are carotenoid-derived phytohormones and rhizosphere signaling molecules for arbuscular mycorrhizal fungi and root parasitic weeds. Why and how plants produce diverse SLs are unknown. Here, cytochrome P450 CYP722C is identified as a key enzyme that catalyzes the reaction of BC-ring closure leading to orobanchol, the most prevalent canonical SL. The direct conversion of carlactonoic acid to orobanchol without passing through 4-deoxyorobanchol is catalyzed by the recombinant enzyme. By knocking out the gene in tomato plants, orobanchol was undetectable in the root exudates, whereas the architecture of the knockout and wild-type plants was comparable. These findings add to our understanding of the function of the diverse SLs in plants and suggest the potential of these compounds to generate crops with greater resistance to infection by noxious root parasitic weeds
Genome editing in plants using CRISPR type I-D nuclease
Genome editing in plants has advanced greatly by applying the clustered regularly interspaced short palindromic repeats (CRISPRs)-Cas system, especially CRISPR-Cas9. However, CRISPR type Iâthe most abundant CRISPR system in bacteriaâhas not been exploited for plant genome modification. In type I CRISPR-Cas systems, e.g., type I-E, Cas3 nucleases degrade the target DNA in mammals. Here, we present a type I-D (TiD) CRISPR-Cas genome editing system in plants. TiD lacks the Cas3 nuclease domain; instead, Cas10d is the functional nuclease in vivo. TiD was active in targeted mutagenesis of tomato genomic DNA. The mutations generated by TiD differed from those of CRISPR/Cas9; both bi-directional long-range deletions and short indels mutations were detected in tomato cells. Furthermore, TiD can be used to efficiently generate bi-allelic mutant plants in the first generation. These findings indicate that TiD is a unique CRISPR system that can be used for genome engineering in plants
Optimization of CRISPR/Cas9 genome editing to modify abiotic stress responses in plants.
Genome editing using the CRISPR/Cas9 system can be used to modify plant genomes, however, improvements in specificity and applicability are still needed in order for the editing technique to be useful in various plant species. Here, using genome editing mediated by a truncated gRNA (tru-gRNA)/Cas9 combination, we generated new alleles for OST2, a proton pump in Arabidopsis, with no off-target effects. By following expression of Cas9 and the tru-gRNAs, newly generated mutations in CRIPSR/Cas9 transgenic plants were detected with high average mutation rates of up to 32.8% and no off-target effects using constitutive promoter. Reducing nuclear localization signals in Cas9 decreased the mutation rate. In contrast, tru-gRNA Cas9 cassettes driven by meristematic- and reproductive-tissue-specific promoters increased the heritable mutation rate in Arabidopsis, showing that high expression in the germ line can produce bi-allelic mutations. Finally, the new mutant alleles obtained for OST2 exhibited altered stomatal closing in response to environmental conditions. These results suggest further applications in molecular breeding to improve plant function using optimized plant CRISPR/Cas9 systems
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