One of the recent CRISPR applications is to edit the
family of genes resulting in bacterial blight in rice caused by Xanthomonas
oryzae pv. Oryzae; which is a huge problem in ASEAN nations. These bacteria
have effector TAL proteins (transcription activator-like) that transcriptionally
activate SWEET genes. Crispr Cas 9 was used to mutate the coder region in the SWEET
gene family thus inhibiting the binding of transcription activator like
bacterial proteins to the promoter. Reduced binding resulted in no induction of
expression of the SWEET genes. Therefore, TAL proteins were unable to induce
disease susceptibility in rice (Pennisi, 2013).

CRISPR Cas9 induced mutations in endogenous plant
genes are easily detected in T0 rice plant and most of these mutations are
inherited in progenies. No off-target mutations in multiple CRISPR/Cas9
transgenic lines have been detected other than the low-frequency off-target mutations,
which indicates that the mutagenesis effect of CRISPR/Cas9 is very specific in
rice. This homozygous specificity in the targeted gene was achieved in just one
generation (Zhang et al., 2014). Other studies have shown large chromosomal
segment deletions and inheritance of genome edits in multiple generations in
rice for high-efficiency, multiplex gene targeting (Zhou et al., 2014). A
parallel technique was used to develop citrus canker and greening disease resistant
citrus trees. .

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Effector protein from Xanthomonas citri and Candidatus
Liberibacter asiaticus binds to the promoter region of the canker gene CsLOB1
inducing diseases. CRISPR Cas 9 can effectively target the coding region of the
citrus susceptibility gene and mutate it to avert binding of bacterial
transducers (Jia et al., 2017). CRISPR does not leave behind any fingerprint or
exogenous DNA in the plants making it significantly different from traditional
GMO crops. Although CRISPR gene editing is successful in rice and barley, it has
not worked on wheat, which showed results with TALENs instead. Plant biology
lags behind in adopting new technologies for genome editing because of lower
funding as compared to research involving animals. Moreover, it is easier to
get the components of CRISPR/Cas9 through the cell lines in case of animals
rather than plants, which exhibit thick cell walls.