Department of Plant Protection, University College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran.
German Collection of Microorganisms and Cell Cultures, DSMZ, Braunschweig, Germany.
J Gen Virol. 2013 Nov;94(Pt 11):2557-2568. doi: 10.1099/vir.0.055434-0. Epub 2013 Aug 12.
The genetic variation and population structure of Soybean mosaic virus (SMV) in Iran was analysed through the characterization of a set of isolates collected in the soybean-growing provinces of Iran. The partial nucleotide sequence of these isolates showed a single, undifferentiated population with low genetic diversity, highly differentiated from other SMV world populations. These traits are compatible with a population bottleneck associated with the recent introduction of SMV in Iran. Phylogenetic analyses suggest that SMV was introduced into Iran from East Asia, with at least three introduction events. The limited genetic diversification of SMV in Iran may be explained by strong negative selection in most viral genes eliminating the majority of mutations, together with recombination purging deleterious mutations. The pathogenicity of Iranian SMV isolates was typified on a set of soybean differential lines either susceptible or carrying different resistance genes or alleles to SMV. Two pathotypes were distinguished according to the ability to overcome Rsv4 resistance in line V94-5152. Amino acid sequence comparisons of virulent and avirulent isolates on V94-5152 (Rsv4), plus site-directed mutagenesis in a biologically active cDNA clone, identified mutation S1053N in the P3 protein as the determinant for virulence on V94-5152. Codon 1053 was shown to be under positive selection, and S1053N-determined Rsv4-virulence occurred in isolates with different genealogies. The V94-5152 (Rsv4)-virulence determinant in Iranian isolates maps into a different amino acid position in the P3 protein than those previously reported, indicating different evolutionary pathways towards resistance breaking that might be conditioned by sequence context.
通过对伊朗大豆种植省份采集的一组分离物的特征分析，研究了大豆花叶病毒（SMV）在伊朗的遗传变异和种群结构。这些分离物的部分核苷酸序列显示出一个单一的、未分化的种群，遗传多样性低，与其他 SMV 世界种群高度分化。这些特征与 SMV 最近在伊朗引入时的种群瓶颈有关。系统发育分析表明，SMV 是从东亚传入伊朗的，至少有三次传入事件。伊朗 SMV 的遗传多样性有限，这可能是由于大多数病毒基因的强烈负选择消除了大多数突变，同时重组清除了有害突变。在一组对 SMV 敏感或携带不同抗性基因或等位基因的大豆差异系上，对伊朗 SMV 分离物的致病性进行了定型。根据在 V94-5152 上克服 Rsv4 抗性的能力，区分了两种致病型。在 V94-5152（Rsv4）上对毒力和无毒力分离物的氨基酸序列比较，加上在生物活性 cDNA 克隆中的定点诱变，确定 P3 蛋白中的 S1053N 突变是 V94-5152 毒力的决定因素。1053 密码子被证明受到正选择，并且在具有不同系统发育的分离物中发生了由 S1053N 决定的 Rsv4 毒力。伊朗分离物中 V94-5152（Rsv4）毒力决定因素在 P3 蛋白中的氨基酸位置与以前报道的不同，表明在抗性打破方面可能存在不同的进化途径，这可能受到序列上下文的影响。
