Scholthof H B, Scholthof K B, Jackson A O
Department of Plant Biology, University of California, Berkeley 94720, USA.
Plant Cell. 1995 Aug;7(8):1157-72. doi: 10.1105/tpc.7.8.1157.
In this study, we analyzed the influence of two nested genes (p19 and p22) of tomato bushy stunt virus (TBSV) on disease symptoms in systemically infected plants and in local lesion hosts. The contribution of individual genes was determined by bioassays with an infectious clone of wild-type TBSV, with p19/p22 mutant derivatives, and by expression of individual TBSV genes from a heterologous potato virus X (PVX) vector. Our results showed that TBSV genes could be expressed at high levels from the PVX vector. The subcellular localization of these proteins as well as the ability of PVX-expressed p22 to trans complement TBSV cell-to-cell movement defective mutants indicate that the exogenously expressed proteins are functionally active. Inoculation studies with TBSV mutants and the PVX derivatives demonstrated that p19 induced a generalized necrosis upon systemic infection of Nicotiana benthamiana and N. clevelandii. In addition, p19 elicited the formation of local necrotic lesions in N. tabacum; however, in N. glutinosa and N. edwardsonii, the local lesion response was activated by p22. These results show that the p19 and p22 proteins of TBSV are important symptom determinants and that closely related plant species may contain different resistance genes that selectively respond to individual TBSV proteins.
在本研究中，我们分析了番茄丛矮病毒（TBSV）的两个嵌套基因（p19和p22）对系统感染植物和局部病斑寄主中病害症状的影响。通过用野生型TBSV的感染性克隆、p19/p22突变体衍生物进行生物测定，以及从异源马铃薯X病毒（PVX）载体表达单个TBSV基因，确定了各个基因的作用。我们的结果表明，TBSV基因可从PVX载体高水平表达。这些蛋白质的亚细胞定位以及PVX表达的p22对TBSV细胞间运动缺陷突变体的反式互补能力表明，外源表达的蛋白质具有功能活性。用TBSV突变体和PVX衍生物进行的接种研究表明，p19在本氏烟草和克利夫兰烟草系统感染后诱导普遍坏死。此外，p19在烟草中引发局部坏死病斑的形成；然而，在黏毛烟草和爱德华氏烟草中，局部病斑反应由p22激活。这些结果表明，TBSV的p19和p22蛋白是重要的症状决定因素，并且亲缘关系密切的植物物种可能含有对单个TBSV蛋白有选择性反应的不同抗性基因。
