Persistence

一些动物已经进化到能够在没有合适的食物来源的情况下长期承受极端环境条件的攻击。植物寄生线虫，更具体地说是胞囊线虫，就是很好的例子。这些微小的动物生活在土壤中，依靠特定种类的寄主植物作为食物来源。目前，对土豆等作物的种植者来说，控制这些专性寄生虫是最大的可变成本。马铃薯孢囊线虫只侵染茄科植物，具有很强的持久性，可以在土壤中休眠数十年后才能侵染作物。保留在雌虫坚硬体壁中的囊卵是能够在没有寄主植物的情况下坚持生存的阶段，并能在不利的土壤温度和水分下生存。这种在土壤中长期存活的能力奠定了它们作为农业上重要的全球病原体的地位。我们最近鉴定了英国马铃薯孢囊线虫种群，它们在田间的寿命不同，即在没有马铃薯作物的情况下，它们的生存能力以不同的速度下降。重要的是，我们还发现土壤中线虫活力下降的速度比之前描述的要慢得多。这一发现对马铃薯孢囊线虫的管理和控制具有重要意义，特别是考虑到英国种植者可用的化学防治选择越来越少。导致这种非凡长寿的具体分子和生化机制仍然没有答案。这些新发现的长寿种群提供了一个独特的机会来了解在广泛的极端环境条件下保护动物的基本过程。在长时间的休眠期间，细胞中包括DNA、RNA、蛋白质和脂肪在内的生物大分子会受到累积的损害。因此，有很大的选择压力，以确保延长休眠的寿命不会影响随后的活力。我们推测，类似于耐脱水的种子，孢囊线虫已经进化出强大的保护和修复机制。CoI-I West的最新进展揭示了基因组维持途径在静止状态下种子延长存活过程中的关键作用。这些特征在厌水生物中广泛共享，为了解和减弱线虫的生命周期提供了一个令人兴奋的新目标。这个项目将结合一系列技术来揭示线虫如何适应在土壤中长期生存。我们将评估在线虫休眠期间积累了多少和什么类型的细胞损伤。我们收集了长达30年休眠期的储存线虫包囊，因此我们可以分析这些包囊，以确定细胞损伤是否会随着时间的推移而增加，以及何时达到影响生存的临界点。我们还将确定在马铃薯孢囊线虫卵复水和解除休眠后基因组维持途径中的DNA修复机制的活性。我们预测，孢囊线虫将需要在休眠期间和休眠后提供针对损害的加强保护的机制。我们将分析和比较休眠、复水和孵化的线虫的全球基因表达，以确定与这些状态相关的主要压力以及保护和修复任何损害的缓解策略。最后，我们将利用我们的主要发现，将新近发现的马铃薯孢囊线虫种群出人意料的超长寿命与分子保护和修复机制的活性联系起来。这将为土壤中线虫寿命的分子基础提供第一个证据，这对开发一套新的控制措施至关重要。

Some animals have evolved to withstand the assault of extreme environmental conditions over long periods when a suitable food source is not available. Plant parasitic nematodes, more specifically the cyst nematodes, are good examples of this. These microscopic animals live in the soil and are dependent on specific species of host plants as food sources. Currently the control of these obligate parasites represents the largest variable cost to growers of crops such as potatoes. The potato cyst nematodes, which can only infect Solanaceous plants, exhibit remarkable persistence and can survive dormant in the soil for decades before emerging to infect crops. Encysted eggs retained in the hardened body wall of the female are the survival stage that is able to persist in the absence of a host plant and survive adverse soil temperature and moisture. This ability to survive long periods in the soil underlies their status as agriculturally important global pathogens. We have recently identified UK populations of potato cyst nematode that vary in their longevity in the field i.e. their viability in the absence of a potato crop declines at different rates. Importantly, we have also found that the rate at which nematode viability declines in the soil can be very much slower than previously described. This finding has important implications for management and control of potato cyst nematode, especially given the dwindling chemical control options available to UK growers. The specific molecular and biochemical mechanisms that allow this extraordinary longevity remain unanswered. These newly-identified long-lived populations offer a unique opportunity to understand the basic processes that protect the animal across a wide range of extreme environmental conditions.Cumulative damage to biological macromolecules including DNA, RNA, proteins and lipids occurs in cells during prolonged periods of dormancy. There is thus strong selection pressure to ensure that extending lifespan in dormancy does not compromise subsequent vigour. We hypothesise that, similar to desiccation-tolerant seeds, cyst nematodes have evolved powerful protection and repair mechanisms. Recent advances by co-I West have revealed crucial roles for genome maintenance pathways in the extended survival of seeds in the quiescent state. These features are shared widely amongst anhydrobiotic organisms and provide an exciting new target for understanding and attenuating the nematode lifecycle.This project will combine a range of techniques to reveal how nematodes have adapted to survive for extended periods in the soil. We will assess how much and what types of cellular damage accumulate during nematode dormancy. We have collections of stored nematode cysts that span a 30 year period of dormancy so we can analyse these to determine if cellular damage increases over time and when it reaches a critical point that affects survival. We will also determine the activity of DNA repair mechanisms that act in genome maintenance pathways after potato cyst nematode eggs rehydrate and are released from dormancy. We predict that cyst nematodes will require mechanisms to provide enhanced protection from damage during and after dormancy. We will analyse and compare global gene expression in dormant, rehydrated and hatched nematodes to identify the predominant stresses associated with these states and the mitigation strategies that protect and repair any damage. Finally, we will use our main findings to correlate the unexpected extreme longevity of recently discovered populations of potato cyst nematode with activity of molecular protect and repair mechanisms. This will provide the first evidence for the molecular basis of nematode longevity in the soil, fundamental to the development of a new suite of control measures.