FIGURE 3.

Schematic diagram of class 2 CRISPR/Cas strategies against viruses and targeting the host genomic DNA. On DNA virus entry into the plant cell, the Cas9/sgRNA complex binds to and cleaves DNA target sites. For RNA viruses or the RNA transcripts of pathogens with DNA genomes, both FnCas9 and Cas13a proteins guided by their cognate sgRNA or crRNA, respectively, have been proven to target and cleave the virus genome or transcripts. Alternatively, host susceptibility factors can be disrupted by CRISPR/Cas9 to perturb viral infection. The plant susceptibility (S) genes can be altered by directly targeting their coding regions or by modifying the promoter region sequences to prevent pathogen‐effector binding. In instances where the outcome of disturbing S genes is not extensively studied, the CRISPR toolkit can be used to introduce resistance (R) genes. Using the cellular homology‐directed repair (HDR) machinery, Cas9 can mediate the insertion of an R gene. To avoid whole‐gene disruption, Cas9 base‐editing technology can be used to make specific mutations that are associated with a disease‐resistant trait. This figure was created using Biorender.