Culver J N, Dawson W O
Department of Plant Pathology, University of California, Riverside 92521.
Virology. 1989 Dec;173(2):755-8. doi: 10.1016/0042-6822(89)90592-8.
Specific nucleotide changes in the coat protein gene of tobacco mosaic virus (TMV) have been identified as responsible for the induction of the hypersensitive reaction (HR) in Nicotiana sylvestris. Each of these nucleotide changes resulted in amino acid substitutions in the coat protein. To determine if the altered viral RNA or the altered protein acted directly to elicit the HR, the coat protein translational starts were removed from full-length cDNA clones of the HR-inducing mutant TMV 25 and the systemically infecting TMV U1 strain. Infectious transcripts of these altered genomes failed to induce HR in inoculated leaves of N. sylvestris. These free-RNA mutants moved poorly out of inoculated leaves and produced a systemic mosaic symptom 9 to 12 weeks after inoculation. Infectious viral RNA, from both mutants, was recovered from inoculated and systemic mosaic leaves. Western blot analysis of both inoculated and noninoculated leaves revealed the presence of TMV-encoded 126-kDa protein and the absence of coat protein for both mutants. This study demonstrates that the coat protein of TMV 25 is an elicitor molecule responsible for the induction of HR in N. sylvestris and that the TMV coat protein is not required for the development of systemic mosaic symptoms.
烟草花叶病毒（TMV）外壳蛋白基因中的特定核苷酸变化已被确定为导致野生烟草中过敏反应（HR）的原因。这些核苷酸变化中的每一个都导致了外壳蛋白中的氨基酸替换。为了确定改变的病毒RNA或改变的蛋白质是否直接作用引发HR，从诱导HR的突变体TMV 25和系统感染的TMV U1株系的全长cDNA克隆中去除了外壳蛋白翻译起始位点。这些改变的基因组的感染性转录本未能在野生烟草的接种叶片中诱导HR。这些游离RNA突变体从接种叶片中移动能力很差，并在接种后9至12周产生系统花叶症状。从接种和系统花叶叶片中回收了来自两种突变体的感染性病毒RNA。对接种和未接种叶片的蛋白质免疫印迹分析表明，两种突变体都存在TMV编码的126 kDa蛋白且不存在外壳蛋白。这项研究表明，TMV 25的外壳蛋白是在野生烟草中诱导HR的激发分子，并且系统花叶症状的发展不需要TMV外壳蛋白。
