Deciphering the enigmatic expression mechanism of the newly discovered PIPO gene in the Potyviridae family of plant viruses

植物病毒是全球农作物损失的主要原因之一，每年因减产而损失的收入约为600亿美元。由于实施了代价高昂的控制战略(例如，对在寄主植物之间传播病毒的昆虫进行化学控制、销毁受感染的果园)，收入也受到了损失。更重要的是，病毒导致的作物歉收加剧了饥荒，破坏了发展中国家和依赖自给自足农业的社区的生计。因此，为植物病毒病提供有效的控制措施是维护英国和世界粮食安全战略的重要组成部分。现在，这一点尤其重要，因为人口继续扩大，包括耕地在内的自然资源进一步枯竭。最大和最具经济意义的植物病毒群是马铃薯Y病毒。该病毒家族涵盖了几乎三分之一的已知植物病毒种类，并造成了全世界约一半的病毒作物损害。马铃薯Y病毒、马铃薯A病毒、芜菁花叶病毒、大豆花叶病毒、甘薯羽状斑驳病毒、西葫芦黄花叶病毒、番木瓜环斑病毒、李痘病毒等具有重要农业意义的马铃薯Y病毒和马铃薯Y病毒、马铃薯花叶病毒、大豆花叶病毒、甘薯羽状斑驳病毒、西葫芦黄花叶病毒和李痘病毒。例如，李痘被认为是李子和杏子等核果物种最具破坏性的病毒性疾病(估计未来30年的成本高达100亿欧元)。萝卜花叶病毒在英国和世界范围内尤为重要，它侵染多种农作物，包括许多甘蓝(油菜、卷心菜、花椰菜、萝卜等)、生菜、西葫芦、大黄和萝卜。与此同时，甘薯羽状斑驳马铃薯Y病毒对撒哈拉以南非洲的粮食安全构成了可怕的威胁。我们对病毒在植物中复制和传播的机制感兴趣--这是一场在分子水平上上演的戏剧。诺贝尔奖获得者弗朗西斯·克里克于1958年提出的分子生物学的核心“教条”描述了携带信息的三大类生物化学物质之间的信息传递：遗传信息通过DNA的复制从一代传递到下一代，在生物体内，DNA基因组中编码的基因被‘转录’成‘信使’RNA分子，用于(‘翻译’)指导蛋白质的合成。DNA和RNA的作用主要是作为遗传信息的载体，而蛋白质可以有不同的作用，例如催化重要的化学反应(酶)，或帮助形成细胞的结构和内容物。然而，值得注意的是，大多数植物病毒都有由RNA而不是DNA组成的微小基因组。在大多数情况下，RNA基因组通过盗用宿主细胞的蛋白质合成机制，直接充当病毒蛋白质翻译的信使RNA。其中一些病毒蛋白是病毒用来复制其基因组的酶，而另一些病毒蛋白则用来形成保护性衣壳，在病毒基因组从一个宿主转移到另一个宿主时保护病毒基因组。由于大多数植物病毒基因组直接作为信使RNA，植物病毒进化出了各种不寻常的机制，在蛋白质翻译水平上控制基因的表达。其中一些机制与寄主植物基因使用的机制非常不同，因此是病毒控制策略的潜在靶标。我们的目标是破译我们最近在马铃薯Y病毒中发现的一种全新的、意想不到的翻译机制。翻译机制对于马铃薯Y病毒的感染性是必不可少的，但似乎涉及到全新的机制，这些机制尚未被任何其他病毒或生物体使用。通过弄清楚这一机制，我们希望学习可持续控制马铃薯Y病毒的新方法。我们还希望学习控制基因表达的新机制，这将在生物技术中有用。

Plant viruses are one of the major causes of crop loss world-wide, with revenue lost due to reduced yield amounting to some US$60 billion annually. Revenue is also lost due to the implementation of costly control strategies (e.g. chemical control of insects that transmit viruses between host plants, destruction of infected orchards). More importantly, virus-induced crop failure exacerbates famine and ruins livelihoods in developing nations and communities that rely on subsistence farming. Thus, providing effective control measures for plant viral diseases is a crucial component of strategies for maintaining food security both in the UK and worldwide. This is particularly important, now, as populations continue to expand and natural resources including arable land are further depleted.The largest and most economically important group of plant viruses are the potyviruses. This virus family encompasses almost a third of known plant virus species and is responsible for around half of viral crop damage worldwide. Potyviruses that are of great agricultural significance include potato viruses Y and A, turnip mosaic virus, soybean mosaic virus, sweet potato feathery mottle virus, zucchini yellow mosaic virus, papaya ringspot virus, and plum pox virus. Plum pox, for example, is considered the most devastating viral disease of stone-fruit species such as plum and apricot (estimated costs amounting to 10 billion euro over 30 years). Turnip mosaic virus is particularly important in the UK and worldwide, infecting a huge variety of crops including many brassicas (oilseed rape, cabbage, cauliflower, turnip etc), lettuce, courgette, rhubarb and radish. Meanwhile, sweet potato feathery mottle potyvirus presents a dire threat to food security in sub-Saharan Africa.We are interested in the mechanisms by which viruses replicate and spread within plants - a drama that unfolds at the molecular level. The central 'dogma' of molecular biology, articulated by Nobel Laureate Francis Crick in 1958, describes the transfer of information between the three major classes of information-carrying biological chemicals: genetic information passes from one generation to the next via the replication of DNA and, within an organism, genes encoded within the DNA genome are 'transcribed' into 'messenger' RNA molecules that are used ('translated') to direct the synthesis of proteins. The roles of DNA and RNA are predominantly as carriers of genetic information, while proteins can have varied roles, for example catalyzing important chemical reactions ('enzymes'), or helping to form the architecture of the cell and its contents. Remarkably, however, most plant viruses, have tiny genomes that are made up of RNA instead of DNA. In most cases, the RNA genome serves directly as a messenger RNA for translation of the viral proteins by pirating the host cell's protein synthesis machinery. Some of these virus proteins are enzymes that the virus uses to replicate its genome, while other virus proteins are used to make the protective capsids that protect the viral genome as it is ferried from one host to another.Because most plant virus genomes serve directly as messenger RNAs, plant viruses have evolved a variety of unusual mechanisms for controlling gene expression at the level of protein translation. Some of these mechanisms are extraordinarily different from mechanisms used by host plant genes, and are therefore potential targets for virus control strategies. We aim to decipher a completely new and unsuspected translational mechanism that we recently discovered in the potyviruses. The translational mechanism is essential for potyvirus infectivity, but appears to involve completely novel mechanisms, that are not known to be used by any other virus or organism. By figuring out this mechanism, we hope to learn new ways of sustainably controlling potyviruses. We also hope to learn new mechanisms for controlling gene expression that will be useful in biotechnology.