Plant scientists are now using genome editing tools to explore on gene
function and develop crops for improvement of traits. One of the technical
challenges in using such tools is to efficiently induce precise and
predictable targeted point mutations for crop breeding. Thus, new additional
tools have been developed such as cytidine base editors (CBEs), which are
CRIPR-Cas9 derived tools used to direct cytidine to thymine base conversion.
In dicots, the most stable genomic integration of CRISPR-Cas9 is through
Agrobacterium-mediated transformation. However, elimination of the foreign
DNA may be hard to accomplish, particularly in vegetatively propagated
plants.

Florian Veillet from Institut National de la Recherche Agronomique in
France, together with other researchers targeted the acetolactate synthase
(ALS) gene in tomato and potato by a CBE using Agrobacterium-mediated
transformation. They successfully edited the targeted cytidine bases, which
led to chlorsulfuron-resistant plants with precise base edition efficiency
of up to 71% in tomato. They also produced 12.9% and 10% edited
(transgene-free) tomato and potato plants, respectively. This approach
decreases the unwanted effects that may be caused by random integration of
transgenes into the host
[www.isaaa.org] genome.


The new approach used in the study is expected to introduce new perspectives
for genome engineering by co-edition of the ALS with other genes, leading to
transgene-free plants with new traits.

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