Complete genome seguencing of Soybean mosaic virus two strains(G5, G7H) and characterization of viral protein interactions

Abstract

The complete nucleotide sequences of the genomic RNAs of Soybean mosaic virus strains G5 (SMV G5) and G7H (SMV G7H) were determined and compared with sequences of other SMV strains and potyviruses. The nucleotide and the deduced amino acid sequences between SMV G5 and G7H were greater than 99% indentity. Interestingly, SMV G7H strain caused a severe mosaic or necrosis symptom in many soybean cultivars including Jinpum-1, Jinpum-2 and Sodam that are resistant to SMV G5. SMV viral RNA contained an open reading frame to encode a polyprotein subsequently processed into up to 10 proteins by proteolytic cleavage. To understand the interrelationships among viral protein, interactions between 10 SMV proteins were tested using yeast two hybrid system. Of 10 proteins, CP, HC-Pro, NIa and VPg showed protein-protein interaction in yeast two hybrid system. To search binding domain that is important for CP-CP interaction, CP-CP interaction was further dissected by constructing deletion and site-directed mutants. Deletion of C-terminal portion of CP (CP ΔSE, CP ΔCE) caused the loss of CP-CP self-interacting ability and self-interaction between CP mutants including C-terminal portion was detected. Alanine substitution of aspartate at 250 amino acid position disrupted CP-CP interaction while substitutions at 188, 189, 198, 205 and 218 amino acid position did not. These results indicate that the C-terminal region of CP might contain domain(s) required for CP-CP interaction and virus assembly. CP mutant including N-terminal region was found to interact with HC-Pro, which plays a key role to aphid transmission