Putting the squeeze on PDs - reticulons, plasmodesmata and viral trafficking in plants

植物病毒是一种严重的经济害虫，由于能够有效地控制其移动，在世界范围内造成重大作物损失。所有植物病毒在植物内广泛移动时都非常有效，无论它们在何处复制到高水平，都会导致坏死和产量损失。为了在植物细胞之间移动，所有病毒都利用胞间连丝，即相邻细胞壁上的专门孔。在进化过程中，病毒采取了非常有效的策略来修饰胞间连丝，以便它们的遗传物质可以从一个细胞传递到另一个细胞。所有的植物病毒都编码“运动蛋白”，这是一种与胞间连丝相互作用的特殊蛋白质，使它们扩张，并允许病毒基因组通过胞间连丝。通过孔的中心是一个轴向的膜结构称为桥粒微管，它被认为是与运动蛋白质相互作用的结构。桥粒微管是一种神秘的结构，是植物所特有的，直径仅为15 nm，是自然界中已知的最紧密的膜结构之一。我们假设，最近发现的蛋白质家族，被称为网，功能重塑植物内质网成桥连丝，从而引起每次植物细胞分裂的胞间连丝。我们建议，进一步，网状的连桥小管功能的病毒运动蛋白结合到网状的中央目标，导致增加的运输性能的plasmodesmata.It的争论，了解病毒通过plasmodesmata的机制是中央的发展战略，消除病毒运动在植物中，从而控制在进入阶段的感染。这个项目将“标记”网状蛋白质，以检查它们引起胞间连丝形成的方式。它还将使用遗传策略在植物细胞分裂期间过量产生或消除网衣，以检查对胞间连丝形成的影响。很有可能，网状蛋白质与胞间连丝中的其他重要蛋白质相互作用，而特定的标记网状蛋白质将被用作生化“诱饵”来识别这些未知的蛋白质。该项目还将尝试通过生物化学方法将膜压缩成细管来制造“人工连丝微管”。这些“人造桥连丝”将用于研究病毒运动蛋白如何与桥连丝相互作用，以及研究蛋白质如何能够通过天然胞间连丝。该项目将涉及最先进的显微镜，遗传学，病毒学和细胞生物学的独特组合，以了解植物如何单独能够制造胞间连丝。这些结果将对控制植物细胞之间的物质运动产生深远的影响，特别是以病毒为例的传染性遗传物质的运输。通过对胞间连丝结构和功能的进一步了解，我们的总体目标是开发有效的策略来控制作物物种中的病毒运动。

Plant viruses are a serious economic pest, causing significant crop losses worldwide due to an ability to control their movement effectively. All plant viruses are extremely efficient at moving extensively within plants, causing necrosis and yield losses wherever they replicate to high levels. To move between plant cells, all viruses exploit plasmodesmata, specialised pores in the walls between adjacent cells. During the course of evolution viruses adopted very efficient strategies for modifying plasmodesmata so that their genetic material can be passed from one cell to the next. All plant viruses encode 'movement proteins', specialised proteins that interact with plasmodesmata, causing them to dilate and allow the viral genome to traffic through the pore. Through the center of the pore lies an axial membranous structure known as the desmotubule, and it is with this structure that movement proteins are thought to interact.The desmotubule is an enigmatic structure, unique to plants, and at only 15 nm in diameter is one of the most tightly constricted membrane structures known in nature. We hypothesise that a recently discovered family of proteins, known as the reticulons, function to remodel the plant endoplasmic reticulum into desmotubules, thus giving rise to plasmodesmata each time plant cells divide. We suggest, further, that the reticulons of the desmotubule function as the central target of viral movement proteins that bind to reticulons, causing an increase in the transport properties of plasmodesmata.It is argued that understanding the mechanism by which viruses pass through plasmodesmata is central to the development of strategies for eliminating virus movement in plants, thus controlling infections at the entry stage. This project will 'tag' reticulon proteins to examine the ways in which they give rise to the formation of plasmodesmata. It will also use genetic strategies to overproduce or eliminate reticulons during plant-cell division to examine the effects on the formation of plasmodesmata. It is likely that reticulons interact with other important proteins within plasmodesmata, and specific tagged reticulons will be used as biochemical 'bait' to identify these unknown proteins.The project will also attempt to make 'artificial desmotubules' by constricting membranes into fine tubes biochemically. These 'artificial desmotubules' will be used to study how viral movement proteins interact with desmotubules and to study how proteins are able to pass through native plasmodesmata. The project will involve a unique combination of state-of-the-art microscopy, genetics, virology and cell biology to understand how plants alone are able to make plasmodesmata. The results will have far reaching implications for controlling the movement of substances between plant cells, specifically the transport of infectious genetic material exemplified by viruses. An overall goal, through increased understanding of plasmodesmatal structure and function, is to develop effective strategies for the control of virus movement in crop species.