Gene-for-gene coevolution between Albugo candida and Arabidopsis; mining non-host resistance genes for white rust control in Brassicaceae crops

植物病害导致作物生产的巨大损失，并给农民带来巨大的成本。例如，控制马铃薯枯萎病每年花费英国农民约6000万英镑，亚洲大豆锈病每年花费巴西农民约8亿美元。我们的目标是提供抗性基因，使疾病能够通过遗传而不是化学来控制。为了提供可靠的遗传解决方案，我们需要更好地了解植物及其病原体如何相互作用。白锈属物种在十字花科植物中引起白色锈病（WR），所述十字花科植物包括芸苔属作物（例如西兰花和油菜）和模式植物拟南芥。WR感染的植物变得非常容易受到其他疾病的影响;我们希望了解这种情况发生的基本机制。病原体将称为效应子的分子传递到宿主细胞，干扰宿主免疫机制。植物抗性（R）基因识别这些效应子，然后激活免疫。为了克服R基因，病原体必须通过编码效应子的基因突变来逃避检测。我们的目标是鉴定WR效应子库，而鉴定效应子的最好方法是找到那些被R基因识别的效应子。植物育种家经常通过将野生近缘种的R基因与作物品种杂交来使用它们。然而，单一的R基因可以被破坏抗性的病原体小种迅速克服。我们的目标是从模式植物拟南芥中克隆多个WR抗性（WRR）基因，这些基因对感染芸苔属或其他十字花科作物的WR菌株起作用。通过用多个独立作用的WRR基因转化作物，降低了病原体中的单个突变将产生抗性破坏菌株的风险。在印度、澳大利亚和加拿大，芥菜是一种重要的油料作物，杀真菌剂对贫困农民来说很昂贵，而且WRR来源不足。拟南芥基因已经被鉴定为抗B。juncea菌株的WR;我们的目标是发现和部署更多的这样的基因。亚麻荠的籽油中有25%是有益心脏健康的多不饱和脂肪酸，与鱼油中的多不饱和脂肪酸相同。Sativa对英国WR株系敏感。我们将调查拟南芥的自然遗传变异，以确定和克隆针对这些菌株的其他WRR基因，并验证它们在C。sativa，然后构建多基因堆栈来保护C.我们使用遗传技巧来鉴定拟南芥中对WR的B juncea菌株起作用的WRR基因的变异。然而，这种方法在鉴定对B的抗性变异时并不起作用。甘蓝（花椰菜、花椰菜、布鲁塞尔芽甘蓝）菌株的WR。我们将测试一种不同的技巧，使我们能够突变所有可能赋予B WRR的候选R基因。甘蓝菌株，从而鉴定针对这些菌株的新WRR基因。这样的基因具有提供抗B的优良来源的潜力。为了鉴定被WRR基因识别的来自WR的效应子，我们可以使用农杆菌在烟草叶中瞬时共表达WRR基因与一组各种效应子候选基因，并且如果存在识别，则防御的激活导致叶的浸润部分中的细胞死亡。因此，我们可以确定哪个效应子被哪个WRR基因识别。这些知识对于确保不同的WRR基因确实识别不同的效应子是必不可少的，也是在未来实验中研究每个效应子如何抑制宿主免疫的前奏。这些研究将提供多基因堆栈，应该提供持久的抗性。使用拟南芥模型系统来促进分离多个不同的WRR基因的这种方法的成功，将验证从小麦或马铃薯的野生近缘种克隆多个R基因的概念上类似的方法，以保护作物免受锈病或晚疫病的侵害。

Plant disease results in substantial losses in crop production, and imposes great costs on farmers. For example, control of potato blight costs UK farmers ~ £60M/year, and Asian soybean rust costs Brazilian farmers ~$800M/year. We aim to provide resistance genes that enable disease to be controlled by genetics rather than chemistry.To provide reliable genetic solutions, we need a better understanding of how plants and their pathogens interact. Albugo species cause white rust (WR) disease in crucifer plants, including Brassica crops (eg broccoli and oilseed rape), and the model plant Arabidopsis. WR-infected plants become extremely susceptible to other diseases; we wish to understand the basic mechanisms by which this happens. Pathogens deliver molecules called effectors to host cells that interfere with host immune mechanisms. Plant resistance (R) genes recognize such effectors and then activate immunity. To overcome R genes, pathogens must evade detection by mutations in genes that encode effectors. We aim to identify the WR effector repertoire, and the best way to identify effectors is to find those that are recognized by R genes.Plant breeders often use R genes from wild relatives by crossing them into crop varieties. However, single R genes can be rapidly overcome by resistance-breaking pathogen races. We aim to clone multiple WR resistance (WRR) genes from the model plant Arabidopsis that act against WR strains that infect Brassica or other crucifer crops. By transforming crops with multiple independently acting WRR genes, the risk is reduced that a single mutation in the pathogen will create a resistance-breaking strain. In India, Australia and Canada, Brassica juncea is an important oilseed crop, fungicides are expensive for poor farmers and there are insufficient sources of WRR. Arabidopsis genes have already been identified against B. juncea strains of WR; we aim to discover and deploy additional such genes. The oilseed Camelina sativa has been engineered to produce 25% of its seed oil as "heart-healthy" polyunsaturated fatty acids identical to those in fish oil, but C. sativa is susceptible to UK WR strains. We will survey Arabidopsis natural genetic variation to identify and clone additional WRR genes against these strains, and verify their efficacy in C. sativa, prior to building a multigene stack to protect C. sativa against known UK strains of WR.We used a genetic trick to identify variation in Arabidopsis for WRR genes that act against B juncea strain of WR. However, this trick did not work to identify variation for resistance to B. oleracea (broccoli, cauliflower, Brussels sprouts) strains of WR. We will test a different trick that enables us to mutate all candidate R genes that might confer WRR to the B. oleracea strains, and thus identify new WRR genes against these strains. Such genes have the potential to provide an excellent source of resistance against B. oleracea-infecting WR strains.To identify effectors from WR that are recognized by WRR genes, we can transiently co-express a WRR gene with a set of various effector candidate genes in tobacco leaves using Agrobacterium, and if there is recognition, activation of defence results in cell death in the infiltrated part of the leaf. We can thus identify which effector is recognized by which WRR gene. Such knowledge is essential to ensure that different WRR genes really do recognize different effectors, and also as a prelude to investigating how each effector suppresses host immunity in future experimentsThese studies will provide multigene stacks that should provide durable resistance. Success with this approach using the Arabidopsis model system to facilitate isolation of multiple distinct WRR genes, will validate conceptually similar approaches to cloning multiple R genes from wild relatives of wheat or potato, to protect the crop against rusts or late blight.