Tools for engineering resistance against pathogens in plants

Agricultural losses due to plant pathogens is one of the most serious challenges faced worldwide. Breeding and introgression of R genes into susceptible cultivars are specific but are overcome by pathogen evolution. Genome sequencing and annotation have led to the identification and characterization of specific genes/gene families responsible for pathogenesis both in the host and pathogens. The most effective and sustainable way to manage plant pathogens and crop improvement is to use genetic engineering tools, that utilize the traditional transgene technology along with the latest genome editing. Amongst the various tools that has been developed, RNA interference has been widely used for regulating gene expression and a large number of small RNAs have been reported to have bidirectional movement between the host and the pathogen. Host-induced gene silencing technology is a powerful tool for protecting the host from pathogens which can be induced by expressing dsRNA-producing constructs in the host. Targeted genome editing using artificial nucleases precisely modify the genomes and CRISPR-Cas9 is the most commonly used nuclease for precise genome editing. These technologies have gained wide popularity due to numerous successful examples with gene knockouts, knockdowns, modifications, repression/silencing as well as activation of target genes in crop plants. In this review, we summarize the most recent strategies that have been utilized for exploiting the host and pathogen genes for disease resistance in plants.