Quantitative Genetics of Hybrid Yeasts: overcoming sterility and biotechnological exploitation of diversity

在几千年的现代人类历史中，对作物和动物改良特性的选择受益于繁殖能力。通过选择性育种进行这种改良的人工选择喂养了世界，也给了我们各种各样的狗品种，更快的赛马等。没有繁殖的能力，就会有有限的变异来进行改进。许多植物，包括各种重要作物，如小麦，都是由两个或两个以上亲缘关系密切的物种杂交而来。这些最初是不育的，在进化中处于死胡同，但通过复制基因组克服了它们的不育性。变异仍然可能是有限的，因为可育衍生物可能在历史上只发生过一次，导致变异在那一点上被固定下来，并随着时间的推移通过突变积累起来。通过从杂交品种的亲本物种中引入染色体渐渗来引入新的变异，在作物改良方面投入了大量的努力。在动物中，克服不育是比较困难的，所以像骡子这样的劳动动物只能通过马和驴父母的杂交来改善，并希望通过两种父母的交配所产生的每一头新骡子的特征都有所改善。这是一种不碰运气的方法，效率不高。在与酵母一起发酵的过程中，使用的是杂交酵母，最著名的是窖藏酵母（Saccharomyces carlsbergens）。也有一些用于葡萄酒工业，其他的在自然界中发现。这些是不育的杂交种，无法通过育种进行改良。在这个项目中，我们通过复制几个新的和现有的杂交种的基因组来克服不育障碍，首先确定特定特征的基因，比如为什么窖藏酵母在低温下发酵得更好，然后创造出具有改进甚至新的特征的新的多样化杂交种。我们将产生大量新的杂交品种，并探索其特性，分离出用于酿造和酿酒的有用菌株以及工业生产菌株。我们还将学习杂交的生物学以及它们的两个基因组如何相互作用。最后，我们将回答“骡子会进化吗？”

Selection for improved characteristics of crops and animals over the millennia of modern human history has benefited from the ability to breed. Artificial selection for such improvement through selective breeding feeds the world as well as gives us the wide variety of dog breeds, faster race horses, etc. Without the ability to breed there is limited variation on which to base improvements. Many plants, including various crops of great importance such as wheat, originated from the hybridization of two or more closely related species. These initially were sterile and dead ends in terms of evolution but overcame their sterility by duplicating their genomes. Variation could still be limited in these as the fertile derivatives may have occurred only once in history resulting in variation being fixed at that point and accumulated over time via mutations. A lot of effort goes into crop improvement by introgressing chromosomes from parental species of the hybrids to bring in new variation. In animals it is more difficult to overcome sterility and so working animals such as mules can only really be improved by breeding in the horse and donkey parents and hoping for improved characteristics in each new mules created by mating the two parents. This is a hit or miss approach and not very efficient. In fermentation uses with yeast there are hybrids that are used, the most famous being the lager yeast Saccharomyces carlsbergensis. There are also some used in the wine industry and others are found in nature. These are sterile hybrids which preclude improvement by breeding. In this project we overcome the sterility barrier by duplicating the genomes of several new and existing hybrids, first to determine the genetics of particular characteristics, like why does lager yeast ferment better at cold temperatures, and then to create new diverse hybrids with improved or even new characteristics. We will generate a large number of new hybrids and explore their characteristics, isolating useful strains for use in brewing and wine making as well as industrial production strains. We will also learn about the biology of hybrids and how their two genomes interact. Finally we will answer the question 'Can mules evolve?'