Adaptation of the geminivirus bean yellow dwarf virus to dicotyledonous hosts involves both virion-sense and complementary-sense genes

Bean yellow dwarf virus (BeYDV) and maize streak virus (MSV) belong to the geminivirus genus Mastrevirus and have host ranges confined to dicotyledono us and monocotyledonous species, respectively, To investigate viral determi nants of host range specificity, chimeras were constructed by exchanging th eir coding and non-coding regions, BeYDV chimeras containing MSV ORF V1, OR F V2 or small intergenic region sequences, either individually or in variou s sequential combinations, replicated and produced virus particles in Nicot iana tabacum protoplasts. BeYDV chimeras containing MSV ORFs C1 and C2 and/ or the large intergenic region were unable to replicate. None of the chimer as was able to systemically infect either N, benthamiana or maize. Compleme ntation experiments using BeYDV chimeras containing MSV ORF V1 and/or ORF V 2 suggest that expression of MSV movement protein and/or coat protein preve nts BeYDV movement. The results demonstrate that factors involved in both v iral DNA replication and virus movement are exclusively adapted to either m onocotyledonous or dicotyledonous host backgrounds.