Ares X, Calamante G, Cabral S, Lodge J, Hemenway P, Beachy R N, Mentaberry A
Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, CONICET, and Facultad de Ciencias Exactas y Naturales, UBA, Buenos Aires, Argentina.
J Virol. 1998 Jan;72(1):731-8. doi: 10.1128/JVI.72.1.731-738.1998.
The p24 protein, one of the three proteins implicated in local movement of potato virus X (PVX), was expressed in transgenic tobacco plants (Nicotiana tabacum Xanthi D8 NN). Plants with the highest level of p24 accumulation exhibited a stunted and slightly chlorotic phenotype. These transgenic plants facilitate the cell-to-cell movement of a mutant of PVX that contained a frameshift mutation in p24. Upon inoculation with tobacco mosaic virus (TMV), the size of necrotic local lesions was significantly smaller in p24+ plants than in nontransgenic, control plants. Systemic resistance to tobamoviruses was also evidenced after inoculation of p24+ plants with Ob, a virus that evades the hypersensitive response provided by the N gene. In the latter case, no systemic symptoms were observed, and virus accumulation remained low or undetectable by Western immunoblot analysis and back-inoculation assays. In contrast, no differences were observed in virus accumulation after inoculation with PVX, although more severe symptoms were evident on p24-expressing plants than on control plants. Similarly, infection assays conducted with potato virus Y showed no differences between control and transgenic plants. On the other hand, a considerable delay in virus accumulation and symptom development was observed when transgenic tobacco plants containing the movement protein (MP) of TMV were inoculated with PVX. Finally, a movement defective mutant of TMV was inoculated on p24+ plants or in mixed infections with PVX on nontransgenic plants. Both types of assays failed to produce TMV infections, implying that TMV MP is not interchangeable with the PVX MPs.
p24蛋白是与马铃薯X病毒（PVX）局部移动有关的三种蛋白之一，在转基因烟草植株（烟草品种Xanthi D8 NN）中表达。p24积累水平最高的植株表现出矮小且略带褪绿的表型。这些转基因植株促进了PVX突变体的细胞间移动，该突变体在p24中存在移码突变。用烟草花叶病毒（TMV）接种后，p24阳性植株中坏死局部病斑的大小明显小于非转基因对照植株。在用Ob接种p24阳性植株后，也证明了对烟草花叶病毒的系统抗性，Ob是一种能逃避N基因提供的过敏反应的病毒。在后一种情况下，未观察到系统症状，通过Western免疫印迹分析和回接试验，病毒积累仍很低或检测不到。相比之下，接种PVX后在病毒积累方面未观察到差异，尽管在表达p24的植株上症状比对照植株更严重。同样，用马铃薯Y病毒进行的感染试验表明对照植株和转基因植株之间没有差异。另一方面，当用PVX接种含有TMV移动蛋白（MP）的转基因烟草植株时，观察到病毒积累和症状发展有相当大的延迟。最后，将TMV的一个移动缺陷突变体接种到p24阳性植株上，或与PVX在非转基因植株上进行混合感染。这两种试验都未能产生TMV感染，这意味着TMV MP与PVX MPs不可互换。
