Sequence variability in the HC-Pro coding regions of Korean soybean mosaic virus isolates is associated with differences in RNA silencing suppression
- 482 Downloads
Soybean mosaic virus (SMV), a member of the family Potyviridae, is an important viral pathogen affecting soybean production in Korea. Variations in helper component proteinase (HC-Pro) sequences and the pathogenicity of SMV samples from seven Korean provinces were compared with those of previously characterized SMV isolates from China, Korea and the United States. Phylogenetic analysis separated 16 new Korean SMV isolates into two groups. Fourteen of the new Korean SMV samples belonged to group II and were very similar to U.S. strain SMV G7 and Chinese isolate C14. One isolate in group II, A297-13, differed at three amino acid positions (L54F, N286D, D369N) in the HC-Pro coding sequence from severe isolates and SMV 413, showed very weak silencing suppressor activity, and produced only mild symptoms in soybean. To test the role of each amino acid substitution in RNA silencing and viral RNA accumulation, a series of point mutations was constructed. Substitution of N for D at position 286 in HC-Pro of SMV A297-12 significantly reduced silencing suppression activity. When the mutant HC-Pro of A297-13 was introduced into an infectious clone of SMV 413, accumulation of viral RNA was reduced to less than 3 % of the level of SMV 413 containing HC-Pro of A297-12 at 10 days post-inoculation (dpi) but increased to 40 % of SMV 413(HC-Pro A297-12) at 40 dpi. At 50 dpi RNA accumulation of SMV 413(HC-Pro A297-13) was similar to that of SMV 413(HC-Pro A297-12). However, at 50 dpi, the D at position 286 of HC-Pro in SMV 413(HC-Pro A297-13) was found to have reverted to N. The results showed that 1) a naturally occurring mutation in HC-Pro significantly reduced silencing suppression activity and accumulation of transgene and viral RNAs, and 2) that there was strong selection for revision to wild type when the mutation was introduced into an infectious clone of SMV.
KeywordsTobacco Etch Virus Soybean Mosaic Virus Zucchini Yellow Mosaic Virus Silence Suppressor Korean Isolate
This research was supported by iPET (Korea Institute of Planning and Evaluation for Technology in Food, Agriculture, Forestry and Fisheries), Ministry of Agriculture, Food and Rural Affairs (Project No. 112018-3).
- 11.Chakrabarty R, Banerjee R, Chung SM, Farman M, Citovsky V, Hogenhout SA, Tzfira T, Goodin M (2007) pSITE vectors for stable integration or transient expression of autofluorescent protein fusions in plants: probing Nicotiana benthamiana–virus interactions. Mol Plant Microbe Interact 20:740–750PubMedCrossRefGoogle Scholar
- 12.Cho EK, Choi SH, Cho WT (1983) Newly recognized soybean mosaic virus mutants and sources of resistance in soybeans. Res Rep ORD (SPMU) 25:18–22Google Scholar
- 13.Cho EK, Chung BJ (1976) Studies on identification and classification of soybean virus diseases I. Preliminary studies on a soybean virus disease. Korean J Plant Prot 15:61–68Google Scholar
- 14.Cho EK, Chung BJ, Lee SH (1977) Studies on identification and classification of soybean virus diseases in Korea. Etiology of a necrotic disease of Glycine max. Plant Dis Rep 61:313–317Google Scholar
- 17.Chung BJ, Lee SH, Cho EK, Park HC (1974) Identification of soybean viruses and soybean varietal reactions. Annu Rep Circ 26:137–145Google Scholar
- 35.Kim YH (2000) G7H, a new strain of soybean mosaic virus: its virulence and nucleotide sequence of cylindrical inclusion gene. Ph.D. thesis, Kyungpook National University, Daegu, p 120Google Scholar
- 56.Yambao MLM, Yagihashi H, Sekiguchi H, Sekiguchi T, Sasaki T, Sato M, Atsumi G, Tacahashi Y, Nakahara KS, Uyeda I (2008) Point mutations in helper component protease of clover yellow vein virus are associated with the attenuation of RNA-silencing suppression activity and symptom expression in broad bean. Arch Virol 153:105–115PubMedCrossRefGoogle Scholar