Institute of Plant Protection-National Research Institute, ul. Wł. Węgorka 20, 60-318 Poznań, Poland.
Virol J. 2011 Jun 24;8:318. doi: 10.1186/1743-422X-8-318.
Pepino mosaic virus (PepMV) is considered one of the most dangerous pathogens infecting tomatoes worldwide. The virus is highly diverse and four distinct genotypes, as well as inter-strain recombinants, have already been described. The isolates display a wide range on symptoms on infected plant species, ranging from mild mosaic to severe necrosis. However, little is known about the mechanisms and pattern of PepMV molecular evolution and about the role of individual proteins in host-pathogen interactions.
The nucleotide sequences of the triple gene block 3 (TGB3) from PepMV isolates varying in symptomatology and geographic origin have been analyzed. The modes and patterns of molecular evolution of the TGBp3 protein were investigated by evaluating the selective constraints to which particular amino acid residues have been subjected during the course of diversification. The tridimensional structure of TGBp3 protein has been modeled de novo using the Rosetta algorithm. The correlation between symptoms development and location of specific amino acids residues was analyzed.
The results have shown that TGBp3 has been evolving mainly under the action of purifying selection operating on several amino acid sites, thus highlighting its functional role during PepMV infection. Interestingly, amino acid 67, which has been previously shown to be a necrosis determinant, was found to be under positive selection.
Identification of diverse selection events in TGB3p3 will help unraveling its biological functions and is essential to an understanding of the evolutionary constraints exerted on the Potexvirus genome. The estimated tridimensional structure of TGBp3 will serve as a platform for further sequence, structural and function analysis and will stimulate new experimental advances.
Pepino 花叶病毒（PepMV）被认为是全球范围内感染番茄的最危险病原体之一。该病毒具有高度多样性，已经描述了四个不同的基因型以及株间重组体。这些分离株在感染的植物物种上表现出广泛的症状，从轻度花叶到严重坏死不等。然而，对于 PepMV 分子进化的机制和模式以及单个蛋白质在宿主-病原体相互作用中的作用知之甚少。
对表型和地理来源不同的 PepMV 分离株的三基因块 3（TGB3）的核苷酸序列进行了分析。通过评估特定氨基酸残基在多样化过程中所经历的选择压力，研究了 TGBp3 蛋白的分子进化模式和模式。使用 Rosetta 算法从头开始对 TGBp3 蛋白的三维结构进行建模。分析了特定氨基酸残基位置与症状发展之间的相关性。
结果表明，TGBp3 主要在对几个氨基酸位点起作用的纯化选择作用下进化，从而突出了其在 PepMV 感染过程中的功能作用。有趣的是，先前已显示为坏死决定因子的氨基酸 67 被发现处于正选择之下。
鉴定 TGB3p3 中的多种选择事件将有助于揭示其生物学功能，对于理解 Potexvirus 基因组所施加的进化约束至关重要。估计的 TGBp3 三维结构将作为进一步的序列、结构和功能分析的平台，并将激发新的实验进展。
