Chen Kuan-Chun, Chiang Chu-Hui, Raja Joseph A J, Liu Fang-Lin, Tai Chun-Hsi, Yeh Shyi-Dong
Department of Plant Pathology, National Chung Hsing University, Taichung, Taiwan, ROC.
Mol Plant Microbe Interact. 2008 Aug;21(8):1046-57. doi: 10.1094/MPMI-21-8-1046.
Most strains of Papaya ringspot virus (PRSV) belong to type W, causing severe loss on cucurbits worldwide, or type P, devastating papaya in tropical areas. While the host range of PRSV W is limited to plants of the families Chenopodiaceae and Cucuribitaceae, PRSV P, in addition, infects plants of the family Caricaceae (papaya family). To investigate one or more viral genetic determinants for papaya infection, recombinant viruses were constructed between PRSV P-YK and PRSV W-CI. Host reactions to recombinant viruses indicated that the viral genomic region covering the C-terminal region (142 residues) of NIaVPg, full NIaPro, and N-terminal region (18 residues) of NIb, is critical for papaya infection. Sequence analysis of this region revealed residue variations at position 176 of NIaVPg and positions 27 and 205 of NIaPro between type P and W viruses. Host reactions to the constructed mutants indicated that the amino acid Lys27 of NIaPro determines the host-specificity of PRSV for papaya infection. Predicted three-dimensional structures of NIaPros of parental viruses suggested that Lys27 does not affect the protease activity of NIaPro. Recovery of the infected plants from certain papaya-infecting mutants implied involvement of other viral factors for enhancing virulence and adaptation of PRSV on papaya.
大多数番木瓜环斑病毒（PRSV）毒株属于W型，在全球范围内对葫芦科作物造成严重损失，或属于P型，在热带地区对番木瓜具有毁灭性。虽然PRSV-W的宿主范围仅限于藜科和葫芦科植物，但PRSV-P还能感染番木瓜科（番木瓜属）植物。为了研究番木瓜感染的一个或多个病毒遗传决定因素，构建了PRSV-P-YK和PRSV-W-CI之间的重组病毒。宿主对重组病毒的反应表明，覆盖NIaVPg C末端区域（142个残基）、完整的NIaPro和NIb N末端区域（18个残基）的病毒基因组区域对番木瓜感染至关重要。该区域的序列分析揭示了P型和W型病毒之间NIaVPg第176位以及NIaPro第27位和第205位的残基差异。宿主对构建的突变体的反应表明，NIaPro的氨基酸Lys27决定了PRSV对番木瓜感染的宿主特异性。亲本病毒NIaPro的预测三维结构表明，Lys27不影响NIaPro的蛋白酶活性。从某些感染番木瓜的突变体中恢复受感染植物意味着其他病毒因子参与增强PRSV对番木瓜的毒力和适应性。
