Genome evolution following transition to separate sexes

同一物种的雄性和雌性往往彼此有很大的不同(即表现出性别二型性)。事实上，在一些物种中，性别之间的差异可能比不同物种甚至不同属的个体之间的差异更大。在人类中，这些差异(例如行为)部分是文化上的，但在很大程度上是由基因决定的。这比表面上看起来更令人惊讶，因为两性共享几乎相同的一组基因，为了从共同的基因库中构建不同的男性和女性表型，必须进化出不同的调控途径。当一个物种从两性状态转变为雌雄异体(雌雄异株)时，需要多长时间才能形成性别二型性？当这种转变发生时，在基因组水平上会发生什么？这些问题将在这个项目中使用一种仅在数百万年前进化出雌雄异株和性染色体的植物物种来解决。与大多数植物不同，宽叶银杉具有独立的雄性和雌性，个体发育为雄性还是雌性取决于Y染色体的存在或不存在，这与许多动物物种(例如人类)的情况没有什么不同。然而，与性染色体相当古老(约2亿年)的人类不同，宽叶木兰进化的性染色体相对较晚，在最近的1000万年内，这为研究其进化最有趣的早期阶段的进化过程提供了机会。这个项目将使用高通量的DNA测序来‘读取’宽叶海棠的基因组，并将其与近缘物种普通海鞘的基因组进行比较，后者既没有单独的性别，也没有性染色体。比较这两个基因组，将有可能研究宽叶木兰的基因组在向该物种的不同性别转变后如何进化。

Males and females of the same species are often quite different from each other (i.e. exhibit sexual dimorphism). In fact, in some species the differences between genders can be stronger than between individuals of different species or even genera. In humans these differences (e.g. in behaviour) are partly cultural, but to a large extent they are determined by genes. This is more surprising than it may seem as the two sexes share almost identical sets of genes and separate regulatory pathways have to evolve in order to build different male and female phenotypes from a shared pool of genes. How long does it take to develop sexual dimorphism when a species switches from a hermaphroditic state to separate sexes (dioecy)? What happens at the genome level when such transition occurs? These questions will be addressed in this project using a plant species that evolved dioecy and sex chromosomes only a few million years ago.Unlike most plants, Silene latifolia has separate males and females and whether an individual develops as a male or a female depends on the presence or absence of the Y chromosome, not dissimilar to the situation in many animal species (e.g. in humans). However, unlike humans, where sex chromosomes are quite ancient (~200 million years), S. latifolia evolved sex chromosomes relatively recently, within the last ~10 million years, which provides an opportunity to study evolutionary processes at the most interesting early stages of their evolution. This project will use high-throughput DNA sequencing to 'read' the genome of S. latifolia and compare it to the genome of a closely related species Silene vulgaris that does not have separate sexes nor sex chromosomes. Comparing the two genomes it will be possible to study how the genome of S. latifolia evolved following transition to separate sexes in this species.