Carrington J C, Jensen P E, Schaad M C
Institute of Biological Chemistry, Washington State University, Pullman 99164, USA.
Plant J. 1998 May;14(4):393-400. doi: 10.1046/j.1365-313x.1998.00120.x.
The potyvirus cylindrical inclusion (CI) protein, an RNA helicase required for genome replication, was analyzed genetically using alanine-scanning mutagenesis. Thirty-one mutations were introduced into the CI protein coding region of modified tobacco etch virus (TEV) genomes expressing either beta-glucuronidase or green fluorescent protein reporters. Twelve of the mutants were replication-defective in protoplast inoculation assays. Among the 19 replication-competent mutants, several possessed cell-to-cell or long-distance movement defects in tobacco plants. Two mutants, AS1 and AS8, were restricted to single cells in inoculated leaves despite genome amplification levels that were equivalent to that of parental virus. Other mutants, such as AS9 and AS14, were able to move cell to cell slowly but were debilitated in long-distance movement. These data provide genetic evidence for a direct role of CI protein in potyvirus intercellular movement, and for distinct roles of the CI protein in genome replication and movement. In combination with high-resolution ultrastructural analyzes and previous genetic data, these results support a model in which CI protein interacts directly with plasmodesmata and capsid protein-containing ribonucleoprotein complexes to facilitate potyvirus cell-to-cell movement.
马铃薯Y病毒属病毒的柱状内含体（CI）蛋白是基因组复制所需的一种RNA解旋酶，利用丙氨酸扫描诱变技术对其进行了遗传分析。在表达β-葡萄糖醛酸酶或绿色荧光蛋白报告基因的改良烟草蚀纹病毒（TEV）基因组的CI蛋白编码区引入了31个突变。其中12个突变体在原生质体接种试验中复制缺陷。在19个具有复制能力的突变体中，有几个在烟草植株中存在细胞间或长距离移动缺陷。两个突变体AS1和AS8，尽管基因组扩增水平与亲本病毒相当，但在接种叶片中局限于单个细胞。其他突变体，如AS9和AS14，能够缓慢地在细胞间移动，但在长距离移动方面减弱。这些数据为CI蛋白在马铃薯Y病毒属病毒细胞间移动中的直接作用以及CI蛋白在基因组复制和移动中的不同作用提供了遗传学证据。结合高分辨率超微结构分析和先前的遗传学数据，这些结果支持了一个模型，即CI蛋白直接与胞间连丝和含衣壳蛋白的核糖核蛋白复合体相互作用，以促进马铃薯Y病毒属病毒的细胞间移动。
