Understanding ice formation in plants: finding new routes to freezing tolerance (PlantIce).

在包括英国在内的许多国家，由于冬季的冰冻条件，农作物受到严重损害。随着气候变化，这种情况变得更糟，因为不可预测的晚霜或早霜袭击了处于脆弱生长阶段的植物，而这些植物还没有适应冬季条件。植物被霜冻破坏和死亡并不是低温的直接结果，而是因为冰的形成。冰造成的大部分损害是由于植物细胞不再有水可用;它们变得脱水，就像植物正在经历干旱一样。然而，有些植物即使在温度降到零度以下时也能防止冰的形成。复杂的因素决定了它们是否能够做到这一点，从而避免冻结的后果。如果我们想生产出更能适应冬季低温的作物，这些因素显然是值得追求的。在过去的20年里，研究工作一直致力于确定允许某些植物在寒冷条件下生存的基因。这在理解某些植物（而不是其他植物）如何科普冰方面取得了一些成功，但很少导致成功的商业开发。也许令人惊讶的是，很少有人致力于确定植物的特征，这些特征决定了这些破坏性的冰晶是否会形成。我们的建议通过观察植物细胞的外部屏障，即细胞壁来解决我们目前知识中的这一空白。大多数冰首先形成在细胞壁周围以及一个细胞与其相邻细胞壁之间的空间内;因此，这是最重要的观察位置。如果一些植物有“合适的”细胞壁来防止冰的形成，而另一些植物没有，我们需要更多地了解细胞壁的特征，使其成为“合适的”，从而不容易形成冰晶。此外，我们已经从我们自己的研究和其他人的研究中获得了很好的证据，表明细胞壁的组成可以影响植物在冷冻条件下的存活。通过这个项目，我们将确定细胞壁的特征，这些特征决定了冰晶是否以及如何开始形成并继续生长和扩散。为此，我们将联合收割机结合最先进的计算机模拟，告诉我们哪些细胞壁化学成分或结构特征鼓励或阻碍冰的形成，与新的成像技术，将跟踪冰在植物中的形成和传播。基于对冰形成的微观理解，我们将通过这种混合方法实现，我们将研究模式植物拟南芥的基因突变体，已知它们的细胞壁存在特定的改变。通过研究它们对零度以下温度的反应，我们将发现这些改变的细胞壁特性中的哪一个与避冰和耐冻性有关。特别是，我们将测量整个植物和单个细胞在冷冻条件下的存活情况，如果它们的细胞壁具有改变的强度或孔隙度;这两个特征被认为是决定抗冻性的重要因素。我们的工作将通过改变细胞壁的效果来识别促进抗冻性的基因。一旦我们确定了拟南芥植物在冷冻条件下生存的重要基因和特征，我们就可以将这些知识应用于作物，立即关注我们所知道的赋予相同特征的作物基因。最终，通过这项工作获得的知识将导致育种，或通过基因改造创造具有提高对冷冻条件的适应力的基因的作物。

In many countries, including the UK, crops suffer severe damage due to freezing conditions during the winter. This has become worse with climate change as unpredictable late or early frosts hit plants at vulnerable growth stages and when they have not been acclimatised to winter conditions.Plants are damaged and killed by frost not as a direct result of the low temperature but because of the effect of ice forming. Much of the damage caused by ice is a consequence of water no longer being available to the plant's cells; they become dehydrated as if the plant was experiencing drought conditions. However, some plant species manage to prevent ice from forming even when the temperature drops below zero degrees. Complex factors determine whether or not they are able to achieve this and thus avoid the consequences of freezing. These factors are clearly worth pursuing if we are to produce crops that are more resilient to low winter temperatures.Over the past 2 decades research effort has been targeted towards identifying the genes that allow some plants to survive freezing conditions. This has met with some success in understanding how some - but not other - plants can cope with ice but has seldom led to successful commercial exploitation. Perhaps surprisingly, little effort has focused on identifying the features of plants that determine whether or not these damaging ice crystals will form. Our proposal addresses this gap in our current knowledge by looking at the outer barrier of the plant cell, the cell wall. Most ice forms first around the cell wall and within the spaces between the walls of one cell and its neighbour; hence, this is the most important place to look. If some plants have "the right kind" of cell walls to prevent ice forming and others do not, we need to understand more about the features of a cell wall that make it the "right kind" and thus less prone to ice crystals. In addition, we already have good evidence from our own research and that of others that the composition of the cell wall can influence plant survival of freezing conditions. Via this project we will identify the features of the cell wall that determine whether and how ice crystals start to form and continue to grow and spread. To this end, we will combine state-of-the-art computer simulations, to tell us which cell wall chemical components or structural features encourage or discourage the formation of ice, with novel imaging techniques that will track ice as it forms and spreads in plants.Building on the microscopic understanding of ice formation we will achieve by this blended methodology, we will investigate genetic mutants of the model plant species Arabidopsis that are known to present specific alterations in their cell wall. By examining how they respond to sub-zero temperatures, we will discover which of these altered cell wall properties are linked with ice avoidance and freezing tolerance. In particular, we will measure how well whole plants and individual cells survive freezing conditions if they have cell walls with altered strength or porosity; two features that are thought to be important in determining freezing tolerance. Our work will identify genes that promote freezing tolerance through their effects on modifying the cell wall. Once we have identified the genes and characteristics that are important for Arabidopsis plants to survive freezing conditions, we can apply this knowledge to crops, focusing immediately on crop genes that we know confer the same characteristics. Ultimately the knowledge gained through this work will lead to breeding, or creation through genetic modification, of crops with genes that confer improved resilience to freezing conditions.