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

在现代人类几千年的历史中，对农作物和动物的改良特征的选择得益于繁殖能力。通过选择性育种进行这种改良的人工选择养活了世界，并为我们提供了种类繁多的狗品种、速度更快的赛马等。如果没有繁殖的能力，就没有有限的变异作为改良的基础。许多植物，包括各种重要的农作物，如小麦，起源于两个或更多近缘物种的杂交。它们最初在进化上是不育的和死胡同，但通过复制它们的基因组克服了它们的不育。变异仍然可能局限于这些，因为可育的衍生品在历史上可能只发生过一次，导致变异固定在那个时间点，并通过突变随着时间的推移而积累。通过导入杂交种亲本物种的染色体来引入新的变异，许多工作都投入到作物改良上。在动物中，克服不孕不育的难度更大，因此，只有通过在马和驴父母中繁殖，并希望通过父母交配产生的每一头新骡子的特征得到改善，才能真正改善骡子等工作动物。这是一种要么击中要么失败的方法，效率不是很高。在酵母菌的发酵使用中，使用了一些杂交种，最著名的是卡尔斯伯根氏酵母。也有一些用于葡萄酒行业，另一些在自然界中发现。这些都是不育的杂交种，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品种的基因组来克服不育障碍，首先确定特定特征的遗传学，例如为什么啤酒酵母在低温下发酵更好，然后创造具有改进甚至新特征的新的多样化杂交品种。我们将产生一大批新的杂交菌株并探索它们的特性，分离出用于酿造和酿酒以及工业生产的有用菌株。我们还将学习杂交种的生物学以及它们的两个基因组如何相互作用。最后，我们将回答这个问题：骡子能进化吗？

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?'