Exploration of Susceptible Genes with Clustered Regularly Interspaced Short Palindromic Repeats–Tissue-Specific Knockout (CRISPR-TSKO) to Enhance Host Resistance

Susceptible (S) genes are those plant genes that facilitate pathogen infection and disease. The loss of function of these genes primarily interrupts the growth and development of invading pathogens and thus makes plants resistant. The S-gene-targeted resistance may produce durable immunity in plants. Because, S gene-based resistance is derived from the inactivation of a host factor required for the survival of a pathogen in the host. To bypass the S gene-based resistance, a parasitic pathogen must evolve and develop the same or similar functions provided naturally by its host factors, which is far more difficult or even may be impossible. However, it is critical to identify and target the appropriate S gene(s) aiming to gain resistant capacity against a particular disease, because S genes may be pathogen-specific in many cases. The clustered regularly interspaced short palindromic repeats (CRISPR) technology has shown great potential in manipulating S genes in plants. The CRISPR-TSKO (CRISPR-based tissue-specific knock-out) tool kit can provide an understanding of the exact function of an individual gene in a tissue and developmental stage-specific manner while also producing a heritable mutant allele. In this review, candidate S genes have been summarized for CRISPR-TSKO mediated tissue-specific gene knockdown to enhance host resistance.