C-T single base editing more efficient than PBE.

Base editor is a new target gene-targeted modification technology based on CRISPR system, which uses cytosine deaminase or artificially evolved adenine deaminase to accurately edit the target site without producing a double-stranded DNA fracture, thus enabling the replacement of C-T or A-G.
at present, the Be3-mediated C-T base editing technology based on the fusion rat cytosine deaminase APOBEC1 has been widely used in plants, but the system still has some defects, such as low editing efficiency, relatively narrow editing active windows and the editing efficiency of GC sequences significantly reduced or not even editing, which limits the application of single-base editing system in plants with precision and diversification.
the High Caixia Research Group of the Institute of Genetics and Developmental Biology of the Chinese Academy of Sciences applied BE3 to the plant genome monobase editing (named PBE System) (Zong et al, Nat.Biotechnol, 2017).
the study used cas9 variants (nCas9-D10A) to fuse human cytosine deaminase APOBEC3A (A3A) and urethraic glycosase (UGI) to form the new single-base editing system A3A-PBE, successfully achieving more efficient C-T monobase editing than PBE in wheat, rice and potatoes.
the protoplasm reporting system and the editing of 10 endogenous gene targets in wheat and rice show that the A3A-PBE editing efficiency can be up to 36.9%, the average C-T editing efficiency is 13.1%, about 13 times higher than the efficiency of PBE, and the window deaminization of this editing system can cover 17 nucleotides of the target sequence, which increases the active value of 10 nucleotides compared to PBE.
more importantly, A3A-PBE editing is not affected by GC sequences, still has efficient editing activity, the efficiency can be as high as 42.1%.
used this technology system to edit the wheat herbicide-resistant gene TaALS and the monoploid-induced gene TaMTL through the instantaneous transformation of the gene gun, with efficiency of 22.5% and 16.7% respectively, and the TaALS mutantshow showed significant resistance to herbicides;
in addition, A3A-PBE can efficiently edit the endogenous genes of potatoes, which is significantly better than PBE, and obtainaes 6.5% editing efficiency of potato mutant plants through protoplasm regeneration.
A3A-PBE base editing system has the advantages of high efficiency, wide de-ammonia window and no sequence preference on target C above, which can broaden the range of plant single base editing.
the establishment of the system is of great technical support to realize the large-scale invivied mutation of plant genome, study the function of plant gene and the role of gene regulation elements.
published the findings online October 1 in the journal Nature Biotechnology, DOI: 10.1038/nbt.4261.
Gao Caixia Research Group' Doctoral Students Zong Yu and Song Luna are the co-first authors of this paper.
research has been supported by the National Nature Fund Commission, the Special Gm Special Project and the Chinese Academy of Sciences.
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