Genetic mapping to mine the genome of the plant Silene latifolia for pseudoautosomal genes, and for future QTL analysis

有很好的证据表明男性和女性的功能之间存在权衡，进化生物学家对这样的情况很感兴趣，即在一种情况下生存或生育的基因在不同的环境中会付出代价。例如，植物或动物在细分的种群中适应其当地环境(这往往涉及权衡，因为不可能同时高度适应许多不同的环境)，或者病原体对其植物或动物宿主的适应(导致特定病原体可以感染的有限宿主范围的进化)。这些情况被认为对维持同一物种个体之间的遗传差异很重要。性别差异(一种基因的一个版本可以提高男性的存活率或生育力，相对于该基因的一个变体拷贝，而女性的性别差异则相反)是这些情况的一个有趣的子集。在进化生物学的速记中，“适应”一词被用来指生存或生育，而这些性冲突的情况被称为“性对抗”。这些差异与细分的种群有一些共同的性质(事实证明，将两性视为不同的种群是有帮助的)，因此，同样可能的是，同一物种的两性之间有时可能保持遗传差异。我们的项目旨在测试这种遗传差异。理论研究已经对这种情况进行了建模，发现这种适应性的性别差异确实会导致一个基因在一个物种群体中最终有两种不同的变异类型，一种类型在男性中最常见，另一种类型在女性中最常见。然而，这是不可能的，除非该基因在性染色体对上，并且对男性有利的基因与Y染色体的男性决定基因有关(而该基因的另一个变体与X染色体有关)。在这种情况下，理论家研究的模型表明，自然选择促进了带有性别拮抗变体的基因和性别决定基因之间的基因重组率降低。这是非常有趣的，因为Y染色体上遗传重组的丧失是致力于了解性染色体进化的生物学家感兴趣的一个主要话题。因此，检测这种行为的基因的一个有利情况是研究这样一个生物体，它的性染色体正在进化过程中，但它仍然有一个大区域，其中包含与性别决定区域进行基因重组的基因。这种基因只有一个已知的例子：在一些鱼类中，性染色体上的基因有一种变异，使雄性有明亮的颜色。这增加了捕食者的显眼程度，因此对雌性不利，但聪明的雄性对雌性更具吸引力，因此具有更高的适合度。然而，这只是一个特例，有必要发现这种遗传变异是否发生在更广泛的范围内。本项目将朝着研究植物--宽叶银杉的性别拮抗的遗传学迈出重要的一步，这是一个很好的选择，因为它已经被证明处于进化性染色体系统的过程中。这项研究建立在以前对该物种的研究以及我们和其他实验室积累的遗传和基因组资源的基础上。我们有一个适合基因图谱的家族，并从一个自然种群中收集了样本，该项目将对我们从该家族中测序的大量基因进行基因图谱，以找到那些位于性染色体重组区域的基因。这一遗传精细图谱将使我们能够使用为作物、植物和家养动物遗传学开发的方法，这些方法可以识别个体的性别拮抗遗传因素。

There is good evidence for trade-offs between male and female functions, and evolutionary biologists are interested in situations like this, when genes that survival or fertility in one circumstance have a cost in a different environment. Examples include adaptation of plants or animals to their local environment in a subdivided population (which often involves trade-offs, because it is not possible simultaneously to be highly adapted to many different environments), or adaptations of pathogens to their plant or animal hosts (leading to the evolution of restricted host ranges that a given pathogen can infect). These situations are thought to be important in maintaining genetic differences between individuals of the same species. Sex differences (with one version of a gene conferring increased males survival or fertility, relative to a variant copy of the gene, and the opposite in females) are one interesting sub-set of these situations. In the shorthand of evolutionary biology, the term "fitness" is used to mean survival or fertility, and these sexual conflict situations are called "sexual antagonism". These differences have some properties in common with subdivided populations (it turns out to be helpful to regard the two sexes as different populations), so it is again likely that genetic differences may sometimes be maintained between the two sexes of the same species. Our project aims to test for such genetic differences.Theoretical studies have modelled such situations have found that such sex differences in fitness, can indeed lead to situations where a gene ends up having two different variant types in a population of species, one type commonest in males, and the other in females. However, this is unlikely unless the gene is on the sex chromosome pair, and the male-beneficial is associated with the male-determining gene of the Y chromosome (while the other variant of the gene is associated with the X chromosome). In this kind of situation, models studied by theoreticians have shown that natural selection promotes a reduced rate of genetic recombination between the gene with the sexually antagonistic variants and the sex-determining gene. This is very interesting, because the loss of genetic recombination on Y chromosomes is a major topic of interest among biologists working to understand the evolution of sex chromosomes. A favorable situation for detecting genes that behave in this way is therefore to study an organism whose sex chromosomes are in the process of evolving, but which still have a large region containing genes that undergo genetic recombination with the sex-determining region. Only one example of such genes is known: in some fish, genes on the sex chromosomes have a variant that makes males have bright coloration. This increases conspicuousness to predators and is therefore disadvantageous to females, but bright males are more attractive to females, and thus have higher fitness. However, this is just a special case, and it is necessary to discover whether this kind of genetic variation occurs more widely.This project will take an important step towards studying the genetics underlying sexual antagonism in a plant, Silene latifolia, which is a good choice because it has been shown to be in the process of evolving a sex chromosome system. The study builds on previous studies in this species, and genetic and genomic resources that we and other labs have accumulated. We have a family suitable for genetic mapping, and have collected samples from a natural population, and the project will genetically map a large number of genes we have sequenced from the family, in order to find those that are in the recombining regions of the sex chromosomes. This genetic fine map will allow us to employ methods developed for crop plant and domesticated animal genetics that can identify individual sexually antagonistic genetic factors.