Unpicking the causes of infertility in wheat triggered by temperature stress

气候变化已经成为世界范围内对农作物生产的严重威胁。目前农业对高温的适应，通过改变农业技术和农场管理，不足以维持产量，需要进一步创新来发展耐热作物。先前的研究已经确定，减数分裂期间的高温高峰是作物生命周期中最脆弱的时期之一，并极大地降低产量(Barber等人，2017年；DOI：10.3389/fpls.2017.00051)。这个项目的目的是：1)更好地了解关键的生殖过程，减数分裂是如何受到合理的极端温度的影响，以及2)测试抗氧化剂的应用是否可以稳定产量。减数分裂是配子形成之前的一种特殊形式的细胞分裂。在减数分裂开始时暴露在高温下会对花粉发育造成多种不利影响。有证据表明，早期减数分裂、染色体配对和重组的中断可能导致染色体的错误分离，导致不平衡。减数分裂是一个高度协调的过程，依赖于细胞骨架进行关键过程(例如，染色体和其他关键结构的移动和正确方向)，其中每个过程都受到高温胁迫的影响(de Storme&Geelen2020；doi.org/10.1038/s420032020897-1)。最终，目前的证据表明，高温对减数分裂的影响会导致不能存活的配子的产生，从而降低肥力和粮食产量。过去的工作采用了一种直截了当的方法来确定温度对减数分裂的影响，但这些条件与田间条件下真实的温度尖峰体验相去甚远。例如，植物会暴露在不切实际的高温下好几天。这使得从生理学研究转向实际应用变得困难。该项目的初步目标将是在雷丁大学开展的工作的基础上再接再厉，在那里使用了一套气候预测(全球气候模型、两个时间段和两个排放情景的集合)来预测英国小麦作物不利天气事件的频率和程度(Harkness等人，2020年；doi.org/10.1016/j.agrformet.2019.107862)。这套气候预测将在受控环境室中重复进行，并测试它们对小麦减数分裂的影响。这项工作将有助于确定预测的气候事件对未来产量的影响程度，以及相对于其他过程对减数分裂的后续影响。Rothamsted Research之前的工作调查了一组春小麦基因型，并确定了减数分裂耐热性增强的品系(Xu等人，2022年；DOI：10.3389/fpls.2022.886541)。造成感病品种和耐病品种减数分裂细胞反应差异的原因尚不清楚。利用现代细胞学方法，对两轮分裂的主要细胞事件进行分析，以确定热诱导的缺陷。在植物中，热胁迫提高了活性氧物种(ROS)的浓度，破坏了细胞的氧化还原状态。植物细胞中的各种抗氧化剂使氧化剂保持在无毒的水平，这种平衡的任何变化都会损害细胞成分。ROS升高的有害影响可以通过直接应用有效的抗氧化剂来减轻，保护花粉活力和谷物产量(周等人，2020年；/doi.org/10.1038/s41598020-64978-2)。通过测定耐病和感病春小麦减数分裂细胞的氧化还原状态，以确定耐病品种是否加强了ROS管理。此外，在小麦减数分裂开始之前应用外源抗氧化剂的保护作用将被评估。如果成功，它将开辟发展耐热减数分裂的生物技术途径。

Climate change has become a serious worldwide threat to crop production. Current agricultural adaptations to high temperature, via changes in agro-technology and on-farm management are insufficient to sustain yield, and further innovation is required to develop heat-tolerant crops. Previous studies have identified that a high temperature spike during meiosis is one of the most vulnerable periods in the crops lifecycle and drastically reduces yield (Barber et al., 2017; doi: 10.3389/fpls.2017.00051). This project aims to i) better understand how a key reproductive process, meiosis, is impacted by plausible temperature extremes, and ii) test whether the application of antioxidants can stabilise yields.Meiosis is a specialised form of cell division that precedes the formation of gametes. Exposure to high temperature at the onset of meiosis can lead to a multitude of detrimental effects on pollen development. Evidence suggests that disruption of the early stages of meiosis, chromosome pairing, and recombination can result in the mis-segregation of chromosomes, leading to an imbalance. Meiosis is a highly orchestrated process, reliant upon the cytoskeleton for key processes (e.g. movement and correct orientation of chromosomes and other key structures) each of which are affected by high temperature stress (De Storme & Geelen 2020; doi.org/10.1038/s42003-020-0897-1). Ultimately, current evidence suggests that high temperature impacts on meiosis result in the production of unviable gametes, lowering fertility and reducing grain yield. Past work has adopted a blunt approach to determine the effect temperature has on meiosis, but these conditions are far removed from the real-world temperature spikes experience in field conditions. For example, plants are exposed to unrealistically high temperatures for several days. This makes it difficult to move from physiological research to practical applications. An initial goal of this project will be to build on work carried out at the University of Reading where a set of climate projections (an ensemble of global climate models, two time periods and two emission scenarios) were used to predict the frequency and magnitude of adverse weather events for UK wheat crops (Harkness et al., 2020; doi.org/10.1016/j.agrformet.2019.107862). The set of climate projections will be replicated in Controlled Environment Rooms, and their effect on meiosis in wheat assayed. This work will serve to establish the extent to which future yield can be impacted by the predicted climatic events and the consequential effects on meiosis relative to other processes .Previous work carried out by Rothamsted Research surveyed a panel of spring wheat genotypes and identified lines with an enhanced meiotic thermotolerance (Xu et al 2022; doi: 10.3389/fpls.2022.886541). What caused the differences in meiotic cellular response between susceptible and tolerant cultivars has not been determined. Using modern cytological methods, the major cellular events of both rounds of division will be assayed to identify the heat induced defects.In plants heat stress elevates the concentration of reactive oxygen species (ROS) disrupting the cellular redox status. Various antioxidants in plant cells keep oxidants at non-toxic levels, and any change in this balance can damage cellular constituents. The harmful effects of elevated ROS can be mitigated via the direct application of potent antioxidants, protecting both pollen viability and grain yield (Zhou et al., 2020; /doi.org/10.1038/s41598-020-64978-2). The redox status of meiotic cells in tolerant and susceptible spring wheat will be assayed to determine if ROS management is enhanced in the tolerant cultivars. In addition, the protective effects of exogenous antioxidants applied prior to the onset of meiosis will be evaluated in wheat. If successful, it will open-up biotechnological approaches to develop thermotolerant meiosis.