A POINT MUTATION IN THE TOBACCO MOSAIC-VIRUS CAPSID PROTEIN GENE INDUCES HYPERSENSITIVITY IN NICOTIANA-SYLVESTRIS
A POINT MUTATION IN THE TOBACCO MOSAIC-VIRUS CAPSID PROTEIN GENE INDUCES HYPERSENSITIVITY IN NICOTIANA-SYLVESTRIS
复制标题
DOI：
10.1073/pnas.85.1.170
复制
发表时间：
1988-01-01
影响因子：
11.1
通讯作者：
DAWSON, WO
中科院分区：
文献类型：
--
作者：
KNORR, DA;DAWSON, WO
在森林烟草中，N“基因赋予对烟草花叶病毒（TMV）的某些株系的超敏抗性，但不赋予对普通株系的超敏抗性。TMV序列负责诱导局部病变的形成，在这个主机被确定通过使用cDNA克隆构建基因组重组体之间的共同株系基因组和局部病变诱导突变体。为了测定赋予突变体表型的序列，将重组体的体外转录物接种到N. 并观察局部病变或全身感染的形成。将杂交基因组转化为突变表型的突变体的序列位于核苷酸5972和6206之间。该区域的序列分析揭示了突变体中核苷酸6157（胞嘧啶变为尿嘧啶）和6199（腺嘌呤变为鸟嘌呤）处的点突变。6157位的突变改变了衣壳蛋白基因，使其在148位指定为苯丙氨酸而不是丝氨酸;核苷酸6199出现在3“非翻译区。当每个点突变被单独替换到野生型背景中时，仅包含6157处改变的转录本在N上产生局部损伤。而仅含有6199处改变的转录本产生系统性花叶症状。突变的频率进行了检查，通过部分测序病毒体RNA从另外6个独立的局部病变突变。5个突变体在6157处具有与原始突变体相同的改变，并且没有突变体在6199处具有改变。本研究表明，TMV衣壳蛋白基因是多功能的，既编码病毒粒子结构蛋白，又介导侵染N.森林植物。
In Nicotiana sylvestris, the N'' gene confers hypersensitive resistance to some strains of tobacco mosaic virus (TMV) but not to the common strain. TMV sequences responsible for inducing local lesion formation in this host were identified by using cDNA clones to construct genomic recombinants between the common strain genome and a local-lesion-inducing mutant. To assay for sequences conferring the mutant phenotype, in vitro transcripts of recombinants were inoculated onto leaves of N. sylvestris and observed for the formation of either local lesions or a systemic infection. Sequences from the mutant that converted the hybrid genome to the mutant phenotype were located between nucleotides 5972 and 6206. Sequence analysis of this region revealed point mutations in the mutant at nucleotides 6157 (cytosine to uracil) and 6199 (adenine to guanine). The mutation at 6157 changes the capsid protein gene to specify phenylalanine rather than serine at position 148; nucleotide 6199 occurs in the 3'' nontranslated region. When each point mutation was individually substituted into the wild-type background, transcripts containing only the alteration at 6157 produced local lesions on N. sylvestris, whereas transcripts containing only the alteration at 6199 produced systemic mosaic symptoms. The frequency of mutation was examined by partially sequencing virion RNA from six additional independent local-lesion mutants. Five mutants had the same alteration at 6157 as the original mutant and none had the alteration at 6199. This work demonstrates that the capsid protein gene of TMV is multifunctional, both encoding ther virion structural protein and mediating the outcome of infection in N. sylvestris.