A new type of adenine base editor ABE7-10 is used in rice.

On February 22nd, the Zhu Health Research Group of the Shanghai Plant Adversity Biology Research Center of the Chinese Academy of Sciences, with the caption, Precise A. T to G. C base editing in the rice genome, online published in Molecular Plant.
the study reported on the application of a new adenine base editor ABE7-10 in rice.
it can put the rice genome at a specific site on the A. T-base-to-efficient conversion to G. C-base pair.
this study extends the single-base editing tools available in plants and will further promote molecular precision breeding of other crops, such as rice.
base replacement mutation is the most common form of mutation in which one base is replaced by another base.
more and more studies show that most changes in biological traits have mutations in the relevant genes, of which base replacement mutations, i.e. point mutations are most common.
seeking efficient single-base editing technology has always been a hot and difficult point in plant research.
October 2017, the David Liu Laboratory of Harvard University published a research paper on Programmable Base editing of A.T to G. C in genomic DNA without DNA cleavage, reporting on a new type of adenine base editor ABE that can target specific sites in the genome. T-base-to-efficient conversion to G. C-base pair.
the study further expands the current crispR/Cas9-based single-base editing tool.
but ABE is based on E. coli tRNA adenine deaminase, after seven rounds of mutation evolution, although it can be efficient base editing of multiple sites in mammalian cells, but whether it can also be used efficiently in plants is unclear.
based on published results in mammalian cells, Zhu Health Research Group developed a new adenine base editing system in rice.
the researchers synthesized the wild TadA and its mutant form TadA7-10 and connected it to the N-side of Cas9 (D10A) with a specific street, while adding VirD2's nuclear positioning signal peptide (NLS) to the C end of Cas9 (D10A) to form the ABEP1 adenonine base editor.
ABEP1 is expressed in rice by maize-driven promoters.
the researchers first chose to edit the OsSPL14 and SLR1 sites in the rice genome, A. T to G. The efficiency of replacement of C was 26 per cent and 12.5 per cent, respectively.
to prove that the base editor can edit multiple sites at the same time, the study designed a single sgRNA to target multiple sites in the genome at the same time.
results show that multiple sites in the rice genome can be edited by ABEP1 at the same time.
ABEP1 relies on SpCas9 to identify target sites, while SpCas9 identifys target sites on NGG PAM sequences, which limits the editable sites in the rice genome.
In order to further expand the editable sites in the rice genome, the ABEP2 adenine base editor was studied and designed, and its identification target site depended on SaCas9.
and SaCas9 identify target sites depend on the NNGRRT PAM sequence.
fixed-point editing of multiple genes in the rice genome showed that ABEP2 was also able to perform efficient base replacement on target sites, some of which were as efficient as 61.3%.
at the same time, ABEP2 can edit multiple sites at the same time.
after sequencing all edit sites, the researchers found that no site produced base insertion, deletion, or other forms of base replacement, indicating a high degree of accuracy in the adenine base editor.
combined with the base editor of a APOBEC1 enzyme previously developed by the research team, efficient replacement of four different bases of DNA (A-G, T-C, C-T, G-A) can be achieved in the rice genome.
this will further promote the study of the functional genome of rice and have a significant impact on the precise breeding of crop molecules. Hua Kai, a ph.d. doctoral student at the
Anti-Reversal Center, is the first author of the paper and researcher Zhu Health is the author of the newsletter.
biotechnology platform provided technical support for the research, which was funded by the Chinese Academy of Sciences.
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