DNA delivery into tissue cultures is a simple method for expressing
CRISPR-Cas9 and creating genome edits in the plants. This approach, however,
allows strong doses of CRISPR-Cas9 to persist far beyond the incidence of
targeting i.e. until genetic segregation of the Cas9 gene.

Although precision is an inherent quality of CRISPR-Cas9, the strong
persistent doses in numerous cells throughout the life span of the plant is
concerning. Specifically, overexpression of CRISPR-Cas9 could lead to
targeting of numerous other sites in the genome.

University of Arkansas scientists developed an inducible CRISPR-Cas9 system
for controlled genome editing, and demonstrated its efficiency and precision
in rice. CRISPR-Cas9 could be induced by one-step heat-shock treatment
leading to high incidence of targeted mutations in the rice plants that were
inherited by the progeny (Fig. 1). In summary, this inducible CRISPR-Cas9 is
a controlled, reasonably efficient platform for genome editing, and
therefore, a promising tool for improving the precision of genome editing
methods.

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