Desvoyes Bénédicte, Faure-Rabasse Sandrine, Chen Min-Huei, Park Jong-Won, Scholthof Herman B
Department of Plant Pathology and Microbiology, Texas A&M University, 2132 TAMU, College Station, Texas 77843, USA.
Plant Physiol. 2002 Aug;129(4):1521-32. doi: 10.1104/pp.004754.
Tomato bushy stunt virus and its cell-to-cell movement protein (MP; P22) provide valuable tools to study trafficking of macromolecules through plants. This study shows that wild-type P22 and selected movement-defective P22 amino acid substitution mutants were equivalent for biochemical features commonly associated with MPs (i.e. RNA binding, phosphorylation, and membrane partitioning). This generated the hypothesis that their movement defect was caused by improper interaction between the P22 mutants and one or more host factors. To test this, P22 was used as bait in a yeast (Saccharomyces cerevisiae) two-hybrid screen with a tobacco (Nicotiana tabacum) cDNA library, which identified a new plant homeodomain leucine-zipper protein that reproducibly interacted with P22 but not with various control proteins. These results were confirmed with an independent in vitro binding test. An mRNA for the host protein was detected in plants, and its accumulation was enhanced upon Tomato bushy stunt virus infection of two plant species. The significance of this interaction was further demonstrated by the failure of the homeodomain protein to interact efficiently with two of the well-defined movement-deficient P22 mutants in yeast and in vitro. This is the first report, to our knowledge, that a new plant homeodomain leucine-zipper protein interacts specifically and in a functionally relevant manner with a plant virus MP.
番茄丛矮病毒及其细胞间运动蛋白（MP；P22）为研究大分子在植物中的运输提供了有价值的工具。本研究表明，野生型P22和选定的运动缺陷型P22氨基酸替代突变体在通常与运动蛋白相关的生化特性（即RNA结合、磷酸化和膜分配）方面是等效的。由此产生了一个假设，即它们的运动缺陷是由P22突变体与一种或多种宿主因子之间的不适当相互作用引起的。为了验证这一点，在以烟草（Nicotiana tabacum）cDNA文库进行的酵母（Saccharomyces cerevisiae）双杂交筛选中，将P22用作诱饵，鉴定出一种新的植物同源结构域亮氨酸拉链蛋白，该蛋白可重复性地与P22相互作用，但不与各种对照蛋白相互作用。这些结果通过独立的体外结合试验得到了证实。在植物中检测到了宿主蛋白的mRNA，并且在两种植物感染番茄丛矮病毒后其积累增强。同源结构域蛋白在酵母和体外不能与两个明确的运动缺陷型P22突变体有效相互作用，进一步证明了这种相互作用的重要性。据我们所知，这是首次报道一种新的植物同源结构域亮氨酸拉链蛋白与植物病毒运动蛋白以功能相关的方式特异性相互作用。
