Mapping nucleotides in the 126-kDa protein gene that control the differential symptoms induced by two strains of tobacco mosaic virus.
Mapping nucleotides in the 126-kDa protein gene that control the differential symptoms induced by two strains of tobacco mosaic virus.
复制标题
绘制 126 kDa 蛋白质基因中控制由两种烟草花叶病毒株诱导的差异症状的核苷酸。
DOI：
10.1006/viro.1996.0368
复制
发表时间：
1996
期刊：
影响因子：
3.7
通讯作者：
Richard S. Nelson
中科院分区：
文献类型：
--
作者：
M. Shintaku;S. A. Carter;Y. Bao;Richard S. Nelson
烟草花叶病毒的霍姆斯隐蔽（M）株系和U1株系的差异症状决定因子先前被定位到编码126 - kDa蛋白以及183 - kDa蛋白N端三分之二的5' - 共末端开放阅读框（ORF）。这两种蛋白都会影响病毒RNA的积累，但是126 - kDa基因内大片段的功能以及其对症状形成的影响尚不清楚，这些片段与其他相关病毒的类似开放阅读框中的序列并不保守。在当前的研究中，代表每个株系（即MIC - TMV和U1 - TMV）的cDNA克隆在这些非保守区域发生突变，以进一步确定导致烟草产生花叶症状的核苷酸。在MIC - TMV的126 - kDa蛋白开放阅读框内，从MIC - TMV序列到U1 - TMV序列仅有8个核苷酸替换的一个突变体的子代病毒诱导出了类似U1 - TMV的症状。这8个核苷酸中的单个或多个替换进一步确定了对症状调节至关重要的残基。MIC - TMV和U1 - TMV序列中的互补替换并不总是产生诱导出互补可见症状的子代病毒。一些突变体的子代在特定位置包含二次位点自发突变，这些位置已被证明会影响症状表型。对于一部分稳定的定点突变体，系统症状的严重程度与褪绿斑大小或接种叶片上这些褪绿斑中的病毒积累之间没有相关性。
The differential symptom determinants of the Holmes' masked (M) and U1 strains of tobacco mosaic virus previously were mapped to the 5'-coterminal open reading frame (ORF) encoding the 126-kDa protein and the N-terminal two-thirds of the 183-kDa protein. Both proteins influence viral RNA accumulation, but the function of, and impact on, symptom formation by large domains within the 126-kDa gene, which are not conserved with sequences in analogous ORFs from other related viruses, are unknown. In the current study, cDNA clones representing each strain (i.e., MIC-TMV and U1-TMV) were mutated in these nonconserved domains to further define the nucleotides responsible for mosaic symptom induction on Nicotiana tabacum. Progeny virus of a mutant containing only eight nucleotide substitutions from the MIC-TMV sequence to the U1-TMV sequence within the 126-kDa protein ORF of MIC-TMV induced U1-TMV-like symptoms. Single or multiple substitutions among these eight nucleotides further defined residues critical for symptom modulation. Complementary substitutions in the MIC-TMV and U1-TMV sequences did not always yield progeny virus that induced complementary visual symptoms. Progeny of some mutants contained second-site spontaneous mutations at specific positions shown to influence symptom phenotype. For a subset of the stable site-directed mutants, there was no correlation between severity of systemic symptoms and chlorotic lesion size or virus accumulation in these chlorotic lesions on inoculated leaves.