Jacquet C, Ravelonandro M, Dunez J
Station de Pathologie Vegetale, INRA Bordeaux, Villenave d'Ornon, France.
Acta Virol. 1998 Sep;42(4):235-7.
Transgenic plums transformed with the plum pox virus coat protein (PPV CP) gene displayed a resistance to the sharka disease (Ravelonandro et al., 1997). However, the expression of PPV CP in transgenic plants may lead to complementation of deficient characteristic of an incoming potyvirus. Indeed, an aphid-intransmissible strain of zucchini yellow mosaic virus (ZYMV-NAT) could be transmitted when encapsidated by the engineered PPV CP (Lecoq et al., 1993). To control such a risk, new PPV CP constructs were designed and introduced into Nicotiana benthamiana genome. In the first construct, the DAG amino acid triplet involved in the potyvirus aphid-transmission was deleted. The second construct encoded a truncated PPV CP lacking its first 140 amino acids. In the last construct, the nucleotides encoding the charged amino-acids R220, Q221 and D264 localized in the core of the PPV CP were removed. A bacterial expression system was developed to show that these deletions prevent the assembly of the PPV CP subunits. For each construct, several transgenic lines were produced and first challenged with several strains of PPV. Two phenotypes of resistance were observed: recovery and immunity. Their biochemical characterization showed that the resistance was RNA-mediated and therefore can be classified as homology-dependent (Jacquet et al., 1998a). Resistant lines producing high level of wild type or modified PPV CP were then inoculated with ZYMV-NAT to perform an aphid-transmission assay. Results of these experiments demonstrated that the use of modified forms of PPV CP genes in transgenic plants provide a good way to control the biological risks associated with heteroencapsidation (Jacquet et al., 1998b).
用李痘病毒外壳蛋白（PPV CP）基因转化的转基因李子表现出对李痘病的抗性（拉韦洛南德罗等人，1997年）。然而，PPV CP在转基因植物中的表达可能导致传入的马铃薯Y病毒缺陷特性的互补。事实上，当由工程化的PPV CP包裹时，西葫芦黄花叶病毒的一种蚜虫非传播株系（ZYMV-NAT）可以被传播（勒科克等人，1993年）。为了控制这种风险，设计了新的PPV CP构建体并将其引入本氏烟草基因组。在第一个构建体中，删除了参与马铃薯Y病毒蚜虫传播的DAG氨基酸三联体。第二个构建体编码一个缺少前140个氨基酸的截短PPV CP。在最后一个构建体中，去除了位于PPV CP核心区域编码带电荷氨基酸R220、Q221和Dl64的核苷酸。开发了一种细菌表达系统以表明这些缺失阻止了PPV CP亚基的组装。对于每个构建体，产生了几个转基因株系，并首先用几种PPV株系进行挑战。观察到两种抗性表型：恢复和免疫。它们的生化特性表明抗性是由RNA介导的，因此可以归类为同源依赖性（雅克等人，1998a）。然后用ZYMV-NAT接种产生高水平野生型或修饰型PPV CP的抗性株系，以进行蚜虫传播试验。这些实验结果表明，在转基因植物中使用修饰形式的PPV CP基因提供了一种控制与异源包裹相关的生物风险的好方法（雅克等人，1998b）。
