Regulation of adaptive responses to flood-induced hypoxia in Marchantia polymorpha

与动物类似，植物需要氧气才能在它们的栖息地呼吸和茁壮成长。当暴露在光下时，植物通过执行光合作用的绿色组织从水分子中释放氧气。然而，限制气体扩散的条件，如洪水，会导致氧气供应急剧减少。这导致了一种紧张的情况，当不直接导致植物死亡时，就会降低作物的生产力。在英国，2007年夏季袭击英格兰东北部和西米德兰兹郡的洪水事件，以及影响约克郡和萨默塞特的2013/14年冬季洪水事件，估计对农业造成的经济损失超过8400万GB。在某些情况下，每个场的成本已超过200,000 GB。发展中国家的经济对这类事件更加敏感(Shresta等人。2018年)。考虑到这一点，与环境因素一样，洪水压力在限制全球农业产量和限制养活人类人口的可能性方面发挥了更大的作用，特别是考虑到它的快速增长，估计在未来30年内达到90亿。我的团队与诺丁汉大学一起，描述了植物测量环境中可用氧浓度并及时激活适应反应以应对这种压力的机制。利用拟南芥作为模式植物物种，我们发现了一种在动物和真菌中保守的酶，它控制调控蛋白的丰度，介导分子对低氧的反应。此外，我们和来自澳大利亚的同事提供了证据，表明细胞能量动力装置-线粒体-也参与了通过称为ANAC的调节蛋白激活适应性反应的需要。它们通常会结合到细胞膜上，在受到压力的情况下，它们会迅速释放出来，进入细胞核并诱导合成面临压力所需的蛋白质。陆地植物起源于大约5亿年前定居在新兴陆地上的水生祖先。环境特征的这种巨大变化推动了植物进化，使其能够利用机会并克服非水生环境的限制。这些创新导致陆地植物开发出专门的功能，以确保它们在水和氧气供应剧烈波动的环境中取得成功和适应。苔类植物，如多形地钱，在潮湿的生境中茁壮成长，但我们发现它们对长时间的淹没非常敏感，而拟南芥则在一系列环境中定居。这些物种在生理上的几个方面存在很大差异，因此我们希望它们使用替代策略来应对低氧。我们相信，在这种不同形态和生态的植物物种之间识别这一过程的差异和相似之处具有尚未开发的潜力，可以发现有用的和未知的响应氧波动的途径，并激活响应以保护免受氧化应激和允许代谢调节来应对低氧。综上所述，我们将通过最新的技术手段和应用最新的分子分析技术来研究这两个物种(Marchantia和Arabiopsis)对缺氧的响应。通过这样做，我们设想识别和表征涉及植物的氧气感知和氧化胁迫信号的分子机制。我们将比较在Marchantia和拟南芥中建立的机制，并开发策略来诱导或抑制这两个模式物种中的每一种机制，以确定哪些是必需的或更有效地保护植物免受洪水胁迫。我们的最终目标是确定可以有效地转移到作物物种以提高其耐淹性的关键元素或途径。

Similar to animals, plants need oxygen to respire and thrive in their habitat. When exposed to light, plants release oxygen from water molecules through the green tissues that perform photosynthesis. However, conditions that limit gas diffusion, such as flooding, cause a dramatic reduction in oxygen availability. This leads to a stressful situation that diminishes crop productivity, when not directly causing death of the plants. In the UK, flood events such as those of Summer 2007 that hit the North Eastern England and the West Midlands, and of winter 2013/14 that affected Yorkshire and Somerset have been estimated to cause an economic damage to agriculture of over £84 million. In some cases, costs have exceeded £200,000 per farm. Economies of developing countries are even more sensitive to such events (Shresta et al. 2018). Considering this, flooding stress play a major more, along environmental factors, to limit agriculture yield worldwide and restricts the possibility to feed the human population, especially when considering its rapid growth, estimated to reach 9 bn within the next 30 years.Together with the University of Nottingham, my team characterized the mechanism by which plants measure the oxygen concentration available in the environment and activate adaptive response in time to cope with this stress. Using Arabidopsis thaliana as a model plant species, we discovered an enzyme conserved with animals and fungi that controls the abundance of regulatory protein that mediate the molecular response to low oxygen. Moreover, we and colleagues from Australia have provided evidence that the cellular energy powerplants, the mitochondria, also participate to signal the need to activate an adaptive response via regulatory protein called ANACs. These are normally bound to cellular membranes from which they are rapidly released in case of stress, to enter cell nuclei and induce the synthesis of proteins required to face the stress.Land plants derive from aquatic ancestors that colonized emerged lands about 500 M years ago. This big change of ambient feature drove plant evolution towards that enabled to exploit the opportunities and overcome the limitations of nonaquatic environments. These innovations have led land plant to development specialized features that ensure their success and fitness in environments characterized by strong fluctuations in water and oxygen availability. Liverworts, such as Marchantia polymorpha, thrive in humid habitats and yet we found them extremely sensitive to prolonged submergence, while Arabidopsis colonized a range of environments. These species largely differ under several aspects of their physiology, and thus we expect them to use alternative strategies to cope with low oxygen. We believe that the identification of differences and similarities in this process across plant species with such divergent morphology and ecology holds untapped potential to the discovery of useful and yet unknown pathways to response to oxygen fluctuations and activate response that protect from oxidative stress and allow metabolic adjustments to cope with hypoxia.In summary, we will study the response to hypoxia in the two species (Marchantia and Arabidopsis) by means of state-of-the-art technologies and applying the most recent molecular analytic techniques. By doing so, we envisage to identify and characterize the molecular mechanisms involved in oxygen perception and oxidative stress signalling in plants. We will compare the mechanisms set into place in Marchantia and Arabidopsis, and exploit the strategy to induce or repress each mechanism in both model species, to identify those essential or more effective to protect plants from flooding stress. Our final aim is the identification of key elements or pathways that can be effectively transferred to crop species to improve their submergence tolerance.