Cronin S, Verchot J, Haldeman-Cahill R, Schaad M C, Carrington J C
Department of Biology, Texas A & M University, College Station 77843, USA.
Plant Cell. 1995 May;7(5):549-59. doi: 10.1105/tpc.7.5.549.
Transport of viruses from cell to cell in plants typically involves one or more viral proteins that supply dedicated movement functions. Transport from leaf to leaf through phloem, or long-distance transport, is a poorly understood process with requirements differing from those of cell-to-cell movement. Through genetic analysis of tobacco etch virus (TEV; potyvirus group), a novel long-distance movement factor was identified that facilitates vascular-associated movement in tobacco. A mutation in the central region of the helper component proteinase (HC-Pro), a TEV-encoded protein with previously described activities in aphid-mediated transmission and polyprotein processing, inactivated long-distance movement. This mutant virus exhibited only minor defects in genome amplification and cell-to-cell movement functions. In situ histochemical analysis revealed that the mutant was capable of infecting mesophyll, bundle sheath, and phloem cells within inoculated leaves, suggesting that the long-distance movement block was associated with entry into or exit from sieve elements. The long-distance movement defect was specifically complemented by HC-Pro supplied in trans by a transgenic host. The data indicate that HC-Pro functions in one or more steps unique to long-distance transport.
植物中病毒在细胞间的转运通常涉及一种或多种具有专门移动功能的病毒蛋白。通过韧皮部在叶片间的转运，即长距离转运，是一个了解甚少的过程，其所需条件与细胞间移动不同。通过对烟草蚀纹病毒（TEV；马铃薯Y病毒属）的遗传分析，鉴定出一种新型长距离移动因子，它促进烟草中的维管束相关移动。辅助成分蛋白酶（HC-Pro）中央区域的一个突变使长距离移动失活，HC-Pro是一种TEV编码的蛋白，之前已描述其在蚜虫介导的传播和多聚蛋白加工中的活性。这种突变病毒在基因组扩增和细胞间移动功能方面仅表现出轻微缺陷。原位组织化学分析表明，该突变体能够感染接种叶片内的叶肉细胞、维管束鞘细胞和韧皮部细胞，这表明长距离移动障碍与进入或离开筛管分子有关。长距离移动缺陷可由转基因宿主反式提供的HC-Pro特异性互补。数据表明，HC-Pro在长距离转运特有的一个或多个步骤中发挥作用。
