Broadening Virus Resistance Through Gene Pyramiding of <i>eIF4E</i> Family Members

Recessive resistance, achieved through mutations in host susceptibility genes, offers an effective way for controlling plant viruses. One well-studied gene family involved in such resistance is the eukaryotic translation initiation factor 4E (eIF4E) gene family, which includes eIF4E, eIFiso4E and the atypical novel cap-binding protein (nCBP). Although gene pyramiding of the eIF4E family may provide a promising strategy for broadening virus resistance, it has so far been applied only to a limited set of gene combinations and target viruses. To deepen our understanding of the practicality of eIF4E family gene pyramiding, we analysed a comprehensive set of eIF4E family knockout mutants and six phylogenetically diverse viruses. Double-gene mutant lines ncbp eif4e1 and ncbp eifiso4e exhibited resistance to five and three viruses, respectively, due to both additive resistance pyramiding and the emergence of novel resistance resulting from combined mutations. Notably, the observed resistance spectrum included the Comovirus, Tymovirus, Betacarmovirus and Tobamovirus genera, which were not previously linked to the eIF4E family. These results reveal a broader involvement of the eIF4E family in viral susceptibility, which may have previously been overlooked due to functional redundancy among the family members. On the other hand, plant growth assessment revealed a more severe penalty in the ncbp eif4e1 mutant than in the ncbp eifiso4e mutant, underscoring the need to select compatible gene combinations for resistance pyramiding. Collectively, this study highlights both the advantages and potential drawbacks of eIF4E family gene pyramiding and provides insights for the future development of crop varieties with broad-spectrum virus resistance.