Temporal Co-regulation of Pathogenesis in Phytophthora

植物病原体，如马铃薯晚疫病病原体，致病疫霉，如何调节其不同感染阶段的时间，以及在植物感染的特定阶段需要哪些基因？尽管疫霉属（Phytophthora）病害造成了巨大的损失和影响，但我们对这组病原体如何调节和协调植物感染的特定阶段并最终导致疾病发展知之甚少。晚疫病是由致病疫霉（P. infestans）引起的马铃薯最具破坏性的病害，马铃薯是全球第三大粮食作物。辣椒疫霉是一种寄主范围非常广的病原体，是蔬菜的主要威胁，大多数作物对辣椒疫霉没有持久的抗性。因此，由疫霉属病原体引起的作物植物疾病对全球粮食安全构成威胁。欧洲的情况因立法禁止或限制农民用来预防疫霉属疾病的某些化学品而变得更加复杂。病原体种群的变化，加上需要生产更多的食物，减少环境足迹，意味着必须寻求新的疾病控制途径。除了致病疫霉和辣椒疫霉之外，已经鉴定了超过120种疫霉属，它们共同导致几乎所有双子叶作物的重大疾病。有些品种的寄主范围有限，而寄主遗传学和基因组学的资源为鉴定和利用自然抗病性提供了新的机会。然而，其他物种，如P. ramorum和P. kernoclave，正在成为对自然生态系统的威胁，感染了广泛的树木和灌木物种，它们没有共同进化。为了对抗这些，培育抗性不是一个可行的策略。深入了解疫霉属感染生物学是为高度特异性和环境友好的化学防治提供新的下一代靶标，并确定导致植物宿主抗病的新途径所必需的。为了使其成为成功的病原体，疫霉必须在活的植物组织中生长，然后通过产生孢子传播到新的植物中。这需要形成不同的病原体感染结构，这涉及许多不同基因的作用，其中许多基因仅在感染的这些特定阶段活跃。致病疫霉和辣椒疫霉的DNA序列已经揭示了数百种（超过500种）候选毒力因子，这些因子被转移到植物细胞中以促进疾病。这些病原体还具有许多其他潜在的毒力蛋白，但对其知之甚少。通过确定这些候选毒力基因中哪些在植物的特定感染过程中最活跃，该项目将使我们能够确定疫霉如何协调其基因表达以形成专门的感染结构，以及它从宿主植物中获得哪些营养物质。然而，该项目的主要重点是确定启动和调节感染所需的大量基因表达的“开关”。我们将寻找致病疫霉和辣椒疫霉共有的那些调控开关，因为必需的和保守的开关可能更有希望用于以后开发广泛适用的疾病控制策略。由于这些可能是疫霉属疾病发展的中心控制，因此它们功能的破坏也可能严重损害疫霉属引起植物疾病的能力。可以通过鉴定干扰或以其他方式减少疫霉属毒力因子产生的作物植物性状来利用疾病发展的特定阶段下的基因表达。或者，由于我们正在寻找窄宿主范围和宽宿主范围疫霉属物种所共有的调节组分，这些可能是开发新的化学防治剂的有吸引力的靶标，所述化学防治剂也可能对其他卵菌植物病原体具有活性。

How do plant pathogens, such as the potato late blight pathogen, Phytophthora infestans, regulate the timing of their different infection stages, and which genes are required at specific stages of plant infection? Despite the enormous cost and impact of Phytophthora diseases, we know little about how this group of pathogens regulate and coordinate specific stages of plant infection that culminate in disease development.Late blight, caused by P. infestans, is the most devastating disease of potato, the third most important food crop globally. The very broad host range pathogen P. capsici is a major threat to vegetables, against which (durable) resistance is not available in most crops. Crop plant diseases caused by Phytophthora pathogens are thus a threat to global food security. The situation in Europe is compounded by legislation banning or restricting some chemicals that farmers rely on to prevent Phytophthora diseases. Changes in pathogen populations, coupled with the need to produce more food with a diminished environmental footprint, means that new avenues of disease control must be sought. In addition to P. infestans and P. capsici, more than 120 species of Phytophthora have been characterized, which collectively cause significant disease on almost all dicot crops. Some are limited in host range, and the resources for host genetics and genomics provide novel opportunities to identify and harness natural disease resistance. However, others, such as P. ramorum and P. kernoviae, are emerging as threats to natural ecosystems, infecting a broad range of tree and shrub species with which they have not co-evolved. To combat these, breeding for resistance is not a viable strategy. A deep understanding of Phytophthora infection biology is required to provide novel, next generation targets for highly specific and environmentally benign chemical control, and to identify new avenues that lead to disease resistance in plant hosts.In order for it to be a successful pathogen, Phytophthora must grow within living plant tissue and then spread to new plants by producing spores. This requires the formation of different pathogen infection structures, which involves the action of many different genes, many of which are only active at these specific stages of infection. The DNA sequences of P. infestans and P. capsici have revealed hundreds (over 500) of candidate virulence factors that are transferred into plant cells to promote disease. These pathogens also have many other potential virulence proteins about which little is known. By identifying which of these candidate virulence genes are most active during specific infection of plants, this project will allow us, for example, to identify how Phytophthora coordinates its gene expression to form specialised infection structures, and what nutrients it obtains from its host plants. However, the main focus of this project is to identify the 'switches' that initiate and regulate expression of the large numbers of genes required for infection. We will search for those regulatory switches that are common to P. infestans and P. capsici, as essential and conserved are likely to be more promising for later development of broadly applicable disease control strategies. As these are likely to be the central controls of Phytophthora disease development, it is likely that disruption of their function will also severely compromise the ability of Phytophthora to cause plant disease. Gene expression underlying specific stages of disease development could be exploited through identification of crop plant traits that interfere with, or otherwise reduce, production of Phytophthora virulence factors. Alternatively, as we are seeking the regulatory components that are common to both narrow and broad host range Phytophthora species, these may be attractive targets for development of new chemical control agents that may also be active against other oomycete plant pathogens.