<i>Rice Yellow Mottle Virus</i> resistance by genome editing of the <i>Oryza sativa</i> L. ssp. japonica nucleoporin gene <i>OsCPR5.1</i> but not <i>OsCPR5.2</i>

Summary Rice yellow mottle virus (RYMV) causes one of the most devastating rice diseases in Africa. Management of RYMV is challenging. Genetic resistance provides the most effective and environment-friendly control. The recessive resistance locus rymv2 ( OsCPR5 . 1 ) had been identified in African rice ( O. glaberrima ), however, introgression into O. sativa ssp. japonica and indica remains challenging due to crossing barriers. Here, we evaluated whether CRISPR/Cas9 genome editing of the two rice nucleoporin paralogs OsCPR5 . 1 ( RYMV2 ) and OsCPR5 . 2 can be used to introduce RYMV resistance into the japonica variety Kitaake. Both paralogs had been shown to complement the defects of the Arabidopsis atcpr5 mutant, indicating partial redundancy. Despite striking sequence and structural similarities between the two paralogs, only o scpr5 . 1 loss-of-function mutants were fully resistant, while loss-of-function oscpr5 . 2 mutants remained susceptible, intimating that OsCPR5 . 1 plays a specific role in RYMV susceptibility. Notably, edited lines with short in-frame deletions or replacements in the N-terminal domain (predicted to be unstructured) of OsCPR5 . 1 were hypersusceptible to RYMV. In contrast to mutations in the single Arabidopsis AtCPR5 gene, which caused severely dwarfed plants, oscpr5 . 1 and oscpr5 . 2 single knockout mutants show neither substantial growth defects nor symptoms indicative of programmed cell death, possibly reflecting functional redundancy of the isoforms regarding other important functions. The specific editing of OsCPR5 . 1 , while maintaining OsCPR5 . 2 activity, provides a promising strategy for generating RYMV-resistance in elite Oryza sativa lines as well as for effective stacking with other RYMV resistance genes or other traits.