Figure 2.

Theoretical and already tested CRISPR/Cas applications to increase plant resistance toward pathogens. CRISPR/Cas9 can be used to disrupt plant susceptibility (S) genes (such as Eukaryotic translation initiation factor 4E (elf4E)) by targeting coding regions to knock out these genes, or to alter sequences of promoter regions, precluding pathogen effector binding to the promoter and thus disrupting plant susceptibility. In addition, Dead Cas9-based CRISPR systems could be used to overexpression of resistance genes or suppression of S genes. CRISPR-mediated homology-directed repair (HDR) can be used to introduce resistance (R) genes against pathogens in cases where the plant-pathogen interaction (and S genes) is not well studied. To develop pathogen resistance without disrupting or replacing whole genes, CRISPR based base-edition technology can be used to achieve specific mutations (biomimicking) in genes to turn them into resistant genes against pathogens of interest. The native function of CRISPR can be also mimicked directly to target and interfere with the genomes of pathogens of interest without affecting plant genome. For example, CRISPR can interfere with DNA genomes of viruses through DNA-targeting gRNA/Cas9 systems or it can disrupt pathogen’s RNA genomes through RNA-targeting gRNA/Cas13a systems. Loss of function in S genes.