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6.1 Introduction
The past decade has seen massive strides in the direction of development and
identification of technologies that would help in precise targeting of the genome to
create mutations at specific locations or precise insertion of desired sequences in a
particular location. Genome editing, as it is commonly known, is now a routine and
easy practice that is performed in laboratories around the world and on a variety of
organisms. This involves the use of synthetic nucleases that can create DNA double-
stranded breaks (DSBs) and mutations that subsequently arise when the break is
repaired by the endogenous DNA repair mechanism of the organism. Initially,
technologies such as homing-endonucleases or meganucleases [ 1 , 2 ], zinc finger
nucleases (ZFN) [ 3 , 4 ], and transcription activator-like effector nucleases (TALENs)
[ 5 , 6 ] were adopted for targeted edits or changes in a genome. But, in the past few
years, a new technology has come to the fore. Isolated and derived from the pro-
karyotic immune system, the clustered regularly interspaced short palindromic
repeats system (or CRISPR system for short) has had a massive effect on increasing
the feasibility of precision genome editing [ 7 – 11 ].
One of the most attractive features of the CRISPR system is its flexible nature,allowing greater leeway for targeting locations of interest within the genome and
hence causing it to be adopted widely [ 12 – 16 ]. The CRISPR system is a single
sequence or stranded DNA recognition tool and can cause breaks in a specific loca-
tion within the genome. Another added advantage is that the CRISPR/CRISPR-
associated protein (CRISPR/Cas) system can help create modified plants that can
avoid regulatory classifications generally associated with transgenic plants in cer-
tain countries [ 17 ]. Moreover, the simplicity of the components required for such an
experiment is also an added advantage, since CRISPR/Cas depends on only two
components to show its activity: single guide RNA (sgRNA) and CRISPR-associated
protein or effector.
Taking into account the current agricultural scenario and the always present needto have crops with stronger and improved traits such as increased yield or enhanced
pathogen resistance, genome editing has been performed on plants with great
success. The CRISPR system has been quite widely used with plants in the last
couple of years, with research encompassing plants from a wide range of plant fami-
lies and genera. CRISPR has been applied to model plants such as Arabidopsis
thaliana [ 18 – 20 ] and Nicotiana benthamiana [ 10 ] and other important crop plants
such as Solanum tuberosum [ 21 ], Triticum aestivum [ 11 , 22 ], and finally Oryza
sativa [ 7 , 11 , 19 , 20 ]. Consistent research on food crops will greatly benefit the
world as more improved varieties can be identified and obtained by introductions of
targeted mutations and new traits. In this chapter, we will take a brief look at the
origin of the CRISPR system and its journey from existence as a bacterial adaptive
immune system to a genome-editing tool. Light will be shed on the application of
the CRISPR system in crop plants and plants in general along with recent modifica-
tions that increase the efficiency of the system.
A. Bandyopadhyay et al.