Kim K H, Hemenway C
Department of Biochemistry, North Carolina State University, Raleigh 27695-7622, USA.
Virology. 1997 May 26;232(1):187-97. doi: 10.1006/viro.1997.8565.
The putative subgenomic RNA (sgRNA) promoter regions upstream of the potato virus X (PVX) triple block and coat protein (CP) genes contain sequences common to other potexviruses. The importance of these sequences to PVX sgRNA accumulation was determined by inoculation of Nicotiana tabacum NT1 cell suspension protoplasts with transcripts derived from wild-type and modified PVX cDNA clones. Analyses of RNA accumulation by S1 nuclease digestion and primer extension indicated that a conserved octanucleotide sequence element and the spacing between this element and the start-site for sgRNA synthesis are critical for accumulation of the two major sgRNA species. The impact of mutations on CP sgRNA levels was also reflected in the accumulation of CP. In contrast, genomic minus- and plus-strand RNA accumulation were not significantly affected by mutations in these regions. Studies involving inoculation of tobacco plants with the modified transcripts suggested that the conserved octanucleotide element functions in sgRNA accumulation and some other aspect of the infection process.
马铃薯X病毒（PVX）三基因块和外壳蛋白（CP）基因上游假定的亚基因组RNA（sgRNA）启动子区域含有其他马铃薯X病毒属病毒共有的序列。通过用来自野生型和修饰的PVX cDNA克隆的转录本接种烟草NT1细胞悬浮原生质体，确定了这些序列对PVX sgRNA积累的重要性。通过S1核酸酶消化和引物延伸分析RNA积累，表明一个保守的八核苷酸序列元件以及该元件与sgRNA合成起始位点之间的间隔对于两种主要sgRNA种类的积累至关重要。突变对CP sgRNA水平的影响也反映在CP的积累上。相比之下，这些区域的突变对基因组负链和正链RNA的积累没有显著影响。用修饰的转录本接种烟草植株的研究表明，保守的八核苷酸元件在sgRNA积累和感染过程的其他方面发挥作用。
