Mitra Ruchira, Krishnamurthy Konduru, Blancaflor Elison, Payton Mark, Nelson Richard S, Verchot-Lubicz Jeanmarie
Oklahoma State University, Department of Entomology and Plant Pathology, NRC 127, Stillwater, OK 74078, USA.
Virology. 2003 Jul 20;312(1):35-48. doi: 10.1016/s0042-6822(03)00180-6.
Potato virus X (PVX) TGBp1, TGBp2, TGBp3, and coat protein are required for virus cell-to-cell movement. Plasmids expressing GFP fused to TGBp2 were bombarded to leaf epidermal cells and GFP:TGBp2 moved cell to cell in Nicotiana benthamiana leaves but not in Nicotiana tabacum leaves. GFP:TGBp2 movement was observed in TGBp1-transgenic N. tabacum, indicating that TGBp2 requires TGBp1 to promote its movement in N. tabacum. In this study, GFP:TGBp2 was detected in a polygonal pattern that resembles the endoplasmic reticulum (ER) network. Amino acid sequence analysis revealed TGBp2 has two putative transmembrane domains. Two mutations separately introduced into the coding sequences encompassing the putative transmembrane domains within the GFP:TGBp2 plasmids and PVX genome, disrupted membrane binding of GFP:TGBp2, inhibited GFP:TGBp2 movement in N. benthamiana and TGBp1-expressing N. tabacum, and inhibited PVX movement. A third mutation, lying outside the transmembrane domains, had no effect on GFP:TGBp2 ER association or movement in N. benthamiana but inhibited GFP:TGBp2 movement in TGBp1-expressing N. tabacum and PVX movement in either Nicotiana species. Thus, ER association of TGBp2 may be required but not be sufficient for virus movement. TGBp2 likely provides an activity for PVX movement beyond ER association.
马铃薯X病毒（PVX）的TGBp1、TGBp2、TGBp3和外壳蛋白是病毒细胞间移动所必需的。将表达与TGBp2融合的绿色荧光蛋白（GFP）的质粒轰击到叶片表皮细胞中，GFP:TGBp2在本氏烟草叶片中能进行细胞间移动，但在烟草叶片中则不能。在转TGBp1基因的烟草中观察到了GFP:TGBp2的移动，这表明TGBp2在烟草中需要TGBp1来促进其移动。在本研究中，GFP:TGBp2以类似于内质网（ER）网络的多边形模式被检测到。氨基酸序列分析表明，TGBp2有两个假定的跨膜结构域。分别在GFP:TGBp2质粒和PVX基因组中引入两个突变，这些突变位于包含假定跨膜结构域的编码序列中，破坏了GFP:TGBp2与膜的结合，抑制了GFP:TGBp2在本氏烟草和表达TGBp1的烟草中的移动，并抑制了PVX的移动。第三个突变位于跨膜结构域之外，对GFP:TGBp2在内质网中的定位或在本氏烟草中的移动没有影响，但抑制了GFP:TGBp2在表达TGBp1的烟草中的移动以及在这两种烟草中PVX的移动。因此，TGBp2与内质网的结合可能是病毒移动所必需的，但并不充分。TGBp2可能为PVX的移动提供了一种超出与内质网结合的活性。
