Unpicking the causes of infertility in wheat triggered by temperature stress

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.