Recent Trends and Advancements in CRISPR-Based Tools for Enhancing Resistance against Plant Pathogens

Abstract

Targeted genome editing technologies are becoming the most important and widely used genetic tools in studies of phytopathology. The "clustered regularly interspaced short palindromic repeats (CRISPR)" and its accompanying proteins (Cas) have been first identified as a natural system associated with the adaptive immunity of prokaryotes that have been successfully used in various genome-editing techniques because of its flexibility, simplicity, and high efficiency in recent years. In this review, we have provided a general idea about different CRISPR/Cas systems and their uses in phytopathology. This review focuses on the benefits of knock-down technologies for targeting important genes involved in the susceptibility and gaining resistance against viral, bacterial, and fungal pathogens by targeting the negative regulators of defense pathways of hosts in crop plants via different CRISPR/Cas systems. Moreover, the possible strategies to employ CRISPR/Cas system for improving pathogen resistance in plants and studying plant-pathogen interactions have been discussed.

Keywords: CRISPR; genome editing; phytopathology; resistance.

Figure 1

An illustration of the plant defense system. In the diagram, it is illustrated how plant immunity (PTI and ETI), resistance to pathogens induced by ETS, and genes involved in the interaction between plants and pathogens are intricately related. The PAMPs (protein-based antimicrobial peptides) in the extracellular environment are recognized by plasma membrane-localized receptors (PRR) from a variety of pathogen types such as viruses, bacteria, or fungi, and the response is triggered by either the PAMP-triggered immunity (PTI) or the Effector-triggered immunity (ETI). Pathogen effectors are regulatory molecules that modify host proteins to establish their growth and initiate the process of effector-triggered susceptibility (ETS). The kinase cascade also plays a role in the crosstalk between PTI and ETI pathways and in the regulation of systemic acquired resistance (SAR).

Figure 2

The scheme of Cas9 system-based genome-editing for trait improvement. Cas9 protein is involved in the base editing and prime editing to target genes. Gene engineering in a crop could be achieved by turning ON/OFF a gene by editing its promoter sequence or by introducing a foreign gene (transgene), while chromosome engineering could be achieved by translocation or by creating indels.