Loss-of-affinity screening and targeted genome editing converge on an nCBP2 motif critical for CBSV VPg interacting and CBSD disease severity

Cassava is a crucial food security crop in sub-Saharan Africa.A key constraint on production is cassava brown streak disease (CBSD). CBSD is a positive sense RNA virus belonging to the family Potyviridae, genus Ipomovirus.Diseases caused by the family Potyviridae have been found to require the interaction of viral genome-linked protein (VPg) and host eukaryotic translation initiation factor 4E (eIF4E) family members. Cassava encodes five eIF4E-family members: eIF4E, eIF(iso)4E-1, eIF(iso)4E-2, nCBP-1, and nCBP-2.We previously found that cassava ncbp-1 ncbp-2 double mutants exhibited attenuated CBSD symptoms and reduced storage root viral titer.As well, CBSV VPg was found to associate with all cassava eIF4E-family members by co-immunoprecipitation.We used targeted and unbiased mutagenesis of nCBP-2 coupled with protein-protein interaction assays to better understand how the CBSV VPg and eIF4E-family protein complex is assembled.