CRISPR is a prokaryotic defence system that was adapted as a tool for genome editing and has become one of the most important discoveries of this century. CRISPR-associated endonucleases cleave DNA at precise sites, which are marked by complementary short-guided RNA. The recently developed versions of endonucleases are compatible with a broad range of PAM motifs, have a higher specificity and enable a specific nucleotide to be replaced.
- MeSH
- DNA genetika MeSH
- editace genu * MeSH
- endonukleasy genetika metabolismus MeSH
- guide RNA, Kinetoplastida genetika MeSH
- lidé MeSH
- sekvence CRISPR genetika MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- MeSH
- chronická myeloidní leukemie genetika terapie MeSH
- genetická terapie metody trendy MeSH
- genom lidský genetika MeSH
- HIV infekce genetika terapie MeSH
- infekce přenášené vektorem MeSH
- komáří přenašeči genetika MeSH
- liposomy MeSH
- nosiče léků MeSH
- RNA interference fyziologie imunologie MeSH
- sekvence CRISPR * genetika MeSH
We report a comprehensive toolkit that enables targeted, specific modification of monocot and dicot genomes using a variety of genome engineering approaches. Our reagents, based on transcription activator-like effector nucleases (TALENs) and the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system, are systematized for fast, modular cloning and accommodate diverse regulatory sequences to drive reagent expression. Vectors are optimized to create either single or multiple gene knockouts and large chromosomal deletions. Moreover, integration of geminivirus-based vectors enables precise gene editing through homologous recombination. Regulation of transcription is also possible. A Web-based tool streamlines vector selection and construction. One advantage of our platform is the use of the Csy-type (CRISPR system yersinia) ribonuclease 4 (Csy4) and tRNA processing enzymes to simultaneously express multiple guide RNAs (gRNAs). For example, we demonstrate targeted deletions in up to six genes by expressing 12 gRNAs from a single transcript. Csy4 and tRNA expression systems are almost twice as effective in inducing mutations as gRNAs expressed from individual RNA polymerase III promoters. Mutagenesis can be further enhanced 2.5-fold by incorporating the Trex2 exonuclease. Finally, we demonstrate that Cas9 nickases induce gene targeting at frequencies comparable to native Cas9 when they are delivered on geminivirus replicons. The reagents have been successfully validated in tomato (Solanum lycopersicum), tobacco (Nicotiana tabacum), Medicago truncatula, wheat (Triticum aestivum), and barley (Hordeum vulgare).
- MeSH
- genetické inženýrství metody MeSH
- geneticky modifikované rostliny genetika MeSH
- ječmen (rod) genetika MeSH
- pšenice genetika MeSH
- RNA rostlin genetika MeSH
- rostlinné proteiny genetika MeSH
- sekvence CRISPR genetika MeSH
- Solanum lycopersicum genetika MeSH
- TALENs genetika MeSH
- Publikační typ
- časopisecké články MeSH
Bacterial genomics has greatly expanded our understanding of microdiversification patterns within a species, but analyses at higher taxonomical levels are necessary to understand and predict the independent rise of pathogens in a genus. We have sampled, sequenced, and assessed the diversity of genomes of validly named and tentative species of the Acinetobacter genus, a clade including major nosocomial pathogens and biotechnologically important species. We inferred a robust global phylogeny and delimited several new putative species. The genus is very ancient and extremely diverse: Genomes of highly divergent species share more orthologs than certain strains within a species. We systematically characterized elements and mechanisms driving genome diversification, such as conjugative elements, insertion sequences, and natural transformation. We found many error-prone polymerases that may play a role in resistance to toxins, antibiotics, and in the generation of genetic variation. Surprisingly, temperate phages, poorly studied in Acinetobacter, were found to account for a significant fraction of most genomes. Accordingly, many genomes encode clustered regularly interspaced short palindromic repeats (CRISPR)-Cas systems with some of the largest CRISPR-arrays found so far in bacteria. Integrons are strongly overrepresented in Acinetobacter baumannii, which correlates with its frequent resistance to antibiotics. Our data suggest that A. baumannii arose from an ancient population bottleneck followed by population expansion under strong purifying selection. The outstanding diversification of the species occurred largely by horizontal transfer, including some allelic recombination, at specific hotspots preferentially located close to the replication terminus. Our work sets a quantitative basis to understand the diversification of Acinetobacter into emerging resistant and versatile pathogens.
