ABSTRACT
CRISPR-Cas is a bacterial and archaeal adaptable immune system discovered in Escherichia coli in 1987. Later, similar sequences were found in the genomes of other microbes, such as halophilic archaea. CRISPR system works against bacteriophages involving three stages; adaptation, expression, and interference. To understand the CRISPR-Cas-based genome-editing technology, advanced biochemical and structural genomics has been constantly working. Currently, a precise CRISPR-Cas system is available for genome-editing in plants, animals, microbes, and human cell lines, which is based on a single guide RNA instead of two RNA molecules in the natural system. CRISPR-Cas is characterized into two main classes as well as six subclasses [type I to VI] based on interfering complex variations. CRISPR-Cas has been employed for targeted gene modification in a variety of plants ranging from model plants to crops and higher plants like trees. CRISPR toolkit has several tools such as Cas9, dCas9, Cas12, Cas13, base editors and prime editors, which have been demonstrated successfully for modification of simple as well as complex traits. The multiplexing feature of CRISPR technology has made it a method of choice for researchers working with polygenic traits. In this chapter, numerous facets of the CRISPR-Cas system are discussed along with its historical development.
