IDENTIFICATION OF GENES ESSENTIAL FOR FREEZING TOLERANCE AS TARGETS FOR MANIPULATION IN CROPS

来自世界上较冷地区的许多植物，包括英国，由于一种被称为冷驯化的过程，能够在冬季条件下生存下来。园艺师可能对这种现象很熟悉，称之为“冷硬化”，即在秋季生长在寒冷但不结霜的条件下的植物，为随后的冬季冰冻温度做好了更好的准备，更有可能存活下来。无法做到这一点的植物通常会因冬季霜冻而死亡。对于农作物来说，这会造成重大的产量损失。随着世界人口的不断增长，估计在未来40年里，粮食产量将不得不增加70%。为了实现这一目标，我们既需要产量更高的作物，也需要能够经受住我们环境的猛烈攻击的作物。冬季的严寒天气是包括英国在内的世界许多地区农作物严重损失的原因。使农作物能够提高对霜冻等不利环境条件的耐受性将为农业带来好处，这意味着农作物可以在一年中太冷而无法生存的部分时间种植，并允许作物在目前无法使用的地区种植，例如在高海拔和较冷的地区。像人类一样，植物有数千个基因决定它们的特征以及它们可以做什么和不能做什么。与我们不同的是，植物无法离开不利的环境，因此它们的许多基因都参与了帮助它们抵御潜在破坏性条件的过程。每一个基因，无论是人类还是植物，在需要的时候都会被“开启”。当基因被激活时，它们会产生有用的蛋白质，这是一种天然化学物质，每种都有独特的功能。能够冷驯化的植物能够在霜冻中生存下来，是因为它们的基因在启动时会产生蛋白质，这些蛋白质的作用是抵御冰冻条件。有趣的是，这些蛋白质通常也是抵御干旱的强大保护剂。因此，发现这些基因的特性是帮助作物更耐冷耐旱的第一步。我们将通过比较耐冻植物和不耐冻植物的基因构成，发现新的耐寒基因。人类基因组计划中使用的令人兴奋的新技术现在允许我们检查植物的整个遗传密码(组成基因的所有DNA)，以便我们可以寻找耐受和敏感植物的遗传密码的差异。发现DNA中的差异将向我们展示负责耐受植物生存的基因。当这些基因被激活时，它们将产生保护性蛋白质；测试这些蛋白质在植物中的位置将为我们提供关于它们在保护它方面所起作用的信息。如果蛋白质对保护很重要，我们可能会认为大量生产蛋白质的植物会更耐受，因此我们将进行测试，看看情况是否属实。我们将在生长迅速、易于研究的实验室模型植物中进行这些实验，使我们能够在较短的时间内取得更大进展。当我们发现哪些基因对抗冻和抗旱最重要时，我们将把这一知识应用到农作物上：我们将生产出使这些蛋白质含量更高的小麦植株，我们将测试我们生产的植物是否能够更好地抵御冰冻和干旱条件。如果这是成功的，我们产生的信息将对作物生物技术专家和试图培育更多抗霜冻和干旱粮食作物品种的传统育种者有利。

Many plants from the world's cooler regions, including the UK, can survive winter conditions due to a process known as cold acclimation. Gardeners may be familiar with this as "cold hardening", the phenomenon whereby plants grown in cold but not frosty conditions in the autumn become better prepared for the subsequent freezing temperatures of winter and are more likely to survive. Plants that are not able to do this are usually killed by winter frosts. For crop plants this causes major yield losses.With an ever growing world population, it is estimated that food production will have to increase by 70% over the next 40 years. To achieve this we need both better yielding crops and crops that can survive the onslaughts of our environment. Freezing conditions during winter are responsible for severe crop losses in many regions of the world, including the UK. Enabling crop plants to improve their tolerance of adverse environmental conditions such as frost would provide benefits to agriculture, meaning that crops can be grown during parts of the year that would otherwise be too cold for them to survive, and allowing crops to be grown in areas that can currently not be used, for instance at higher altitudes and in colder areas.Like humans, plants have thousands of genes that determine their characteristics and what they can and cannot do. Unlike us, plants cannot move away from unfavourable environments so many of their genes are involved in helping them defend themselves against the potentially damaging conditions they experience. Every gene, whether human or plant, is "switched on" when needed. When genes are switched on they make useful proteins, natural chemicals each with a unique function. Plants that are capable of cold acclimation can survive frosts because they have genes that, when switched on, produce proteins whose role is to protect against freezing conditions. Interestingly, these proteins are also often powerful protectants against drought. Therefore, discovering the identity of such genes is the first step in helping to make crops more tolerant of cold and drought. We will discover new genes for freezing tolerance by comparing the genetic make-up of plants that can tolerate freezing with that of plants that cannot. Exciting new technology of the type used in the human genome project now allows us to examine the entire genetic code (all of the DNA that makes up the genes) of a plant so that we can look for differences in the genetic code of tolerant and susceptible plants. Finding differences in the DNA will show us the genes that are responsible for the survival of tolerant plants. When these genes are switched on they will make protective proteins; testing where in the plant these proteins are found will give us information as to the role they play in protecting it. If the proteins are important for protection, we might expect that plants producing them in larger amounts would be more tolerant, therefore we will test to see if this is indeed the case.We will perform these experiments in a model lab plant that grows quickly and is easy to study, allowing us to make more progress in a shorter time. When we have discovered which genes are most important for freezing and drought tolerance, we will apply this knowledge to a crop plant: we will produce wheat plants that make these proteins in greater abundance and we will test whether or not the plants we have produced can better withstand freezing and drought conditions. If this is successful, the information we have generated will be of benefit to crop biotechnologists and traditional breeders attempting to make more frost- and drought-resistant varieties of food crops.