Genetic modification of crop plants with ribosome-inactivating protein genes for enhanced resistance to pathogens and pests

Genetic engineering has emerged as an attractive strategy for incorporating resistance in plants against diverse pathogens and has been largely achieved through transgenic expression of ribosome-inactivating proteins (RIPs), pathogenesis-related (PR) proteins, pathogen-derived genes, or strategies involving RNA interference and clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 (CRISPR/Cas9) gene editing tool. RIPs are rRNA N-glycosylases that commonly exert their protective effects through suppression of translation by enzymatically inactivating ribosomes, thereby arresting protein synthesis. Additionally, a few RIPs may possess other enzymatic activities viz. superoxide dismutase, chitinase, DNase and phosphatase, contributing towards pathogen resistance in plants. RIPs are mostly produced by plants and conventionally classified into three types. Type I RIPs are monomeric, with catalytic A chains, exhibiting rRNA N-glycosylase activity. Type II RIPs are dimeric, comprising the enzymatically active A chain associated with the lectin B chain enabling an access inside the cells, hence these are often highly toxic. Less common Type III RIPs include the jasmonic acid inducible protein such as JIP-60, with the catalytic domain becoming functional upon removal of an internal peptide segment and following cleavage of a C-terminal domain which resembles the eukaryotic initiation factor 4e. Unusual RIPs and RIP-related proteins, that cannot be grouped into the classical three types of RIPs, because of their difference in size, structure, or function, also exist. Several RIPs have been recombinantly expressed and demonstrated to possess catalytic activity. Plants carrying RIP transgenes exhibit resistance against viruses, fungi and insects. More often, such studies have been carried out using model systems comprising tobacco, potato or tomato, transformed via Agrobacterium tumefaciens, and employing the most widely used promoter such as CaMV 35S, to enable a high-level expression of the RIP gene. This review focuses on the recent developments in the recombinant DNA approach for the modification of crops with RIP genes to reduce the impact of pathogens and pests.

Automated summary

Genetic engineering is an attractive strategy for creating disease-resistant plants by incorporating genes for ribosome-inactivating proteins (RIPs), pathogenesis-related (PR) proteins, pathogen-derived genes, or using RNA interference and CRISPR/Cas9 gene editing tools.