The evolution of chromosome structure meiotic pairing and silencing of the heterologous sex chromosomes in the plant genus Silene

植物属植物染色体结构减数分裂配对的进化与异源性染色体的沉默

• 批准号: BB/E002765/2
• 负责人: Dmitry Filatov
• 金额: $ 28.48万
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2007
• 资助国家: 英国
• 起止时间: 2007 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FE002765%2F2
• 关键词: evolution; chromosome; structure; meiotic; pairing

Human individuals normally develop as either a male or a female and the genetic mechanism that determines the sex of an organism is based on sex chromosomes: Females have two X chromosomes, while males have one X and one Y chromosome, which is male-specific. During embryonic development the individual genes on the Y chromosome trigger a chain of events leading to the development of a male. Apart from the sex chromosomes, cells contain other chromosomes, called autosomes. Each chromosome is normally represented twice, for example, in the human there are 46 chromosomes, consisting of a pair of sex chromosomes and 22 pairs of autosomes. In the egg and sperm the chromosomes are represented once. In order to achieve this the meiotic pathway occurs, the chromosomes form pairs, which is relatively straightforward for the autosomes and XX in females. Things become more complicated when two different sex chromosomes, X and Y, have to pair in males. The cell has to ensure that a correct pairing is formed between the X and Y chromosomes and depends on pairing in a small region that is similar in both chromosomes, known as the pairing region. The mechanisms involved in these processes are studied to some extent in humans and the mouse, but no information is available for independently evolved plant sex chromosomes. Understanding how sex chromosomes have evolved independently in evolution and how they function in different organisms is of great biological interest. In this project we will study how plant sex chromosomes make sure the pairing occurs correctly and how the structure and function of plant sex chromosomes evolved. Plants often have male and female organs on the same individual. Species with separate male and female individuals are rare in plants and some of these species are known to contain sex chromosomes. The white campion, Silene latifolia has separate sexes (male and female plants) and has a sex chromosome system similar to mammals; females have two X chromosomes, while males contain X and Y chromosomes. The sex determination system in this species is relatively young and likely to have evolved 10-15 million years ago (MYA) compared to ~320 MYA in mammals. Sex chromosomes have evolved only in a few species of the genus Silene, allowing us to compare the structure and behaviour of chromosomes in species with and without sex chromosomes. This provides a unique opportunity to study evolutionary changes that have led to sex chromosome evolution. The two questions we want to understand are how have the sex chromosomes evolved in the campions, and how they negotiate meiosis successfully, given the X and Y chromosomes are largely different to each other and therefore have specific problems in pairing, synapsis and recombination. For this purpose we will search for DNA probes that hybridise specifically with S. latifolia sex chromosomes. The location of these probes on the sex chromosomes (and chromosomes homologous to sex chromosomes) in different species will be studied and compared using fluorescent in situ hybridisation, the method which allows to localise fluorescent-labelled DNA probes hybridised to chromosomes fixed to a glass slide. The pairing of sex chromosomes during cell devision (meiosis) will be studied using fluorescent-labelled antibodies, the proteins that specifically bind other proteins, in our case the proteins involved in chromosome pairing and recombination. Using these tools we will be able to observe the paired and unpaired regions of the sex chromosomes as fluorescing foci on chromosome spreads. The comparison of structure and meiotic behaviour of sex chromosomes in Silene on the one hand and mammals on the other will help to understand whether and to what extent meiotic processes and controls are conserved across all eukaryotes. A plant model such as the one provided by the Silene genus is very advantageous and likely to be useful for general principles in meiosis and therefore reproduction in humans.

人类个体通常发育为男性或女性，决定生物体性别的遗传机制基于性染色体：女性有两条X染色体，而男性有一条X和一条Y染色体，这是男性特有的。在胚胎发育过程中，Y染色体上的单个基因触发了一系列导致男性发育的事件。除了性染色体，细胞还含有其他染色体，称为常染色体。每个染色体通常代表两次，例如，在人类中有46条染色体，由一对性染色体和22对常染色体组成。在卵子和精子中，染色体只代表一次。为了实现这一点，减数分裂途径发生，染色体形成配对，这对于女性中的常染色体和XX来说相对简单。当两个不同的性染色体，X和Y，必须在男性中配对时，事情变得更加复杂。细胞必须确保在X和Y染色体之间形成正确的配对，并且取决于在两条染色体中相似的小区域中的配对，称为配对区域。这些过程中涉及的机制在人类和小鼠中进行了一定程度的研究，但没有关于独立进化的植物性染色体的信息。了解性染色体如何在进化过程中独立进化，以及它们在不同生物体中如何发挥作用，具有重大的生物学意义。在这个项目中，我们将研究植物性染色体如何确保配对正确发生，以及植物性染色体的结构和功能如何进化。植物通常在同一个体上有雄性和雌性器官。在植物中，雄性和雌性个体分开的物种是罕见的，其中一些物种已知含有性染色体。白色坎皮翁，宽叶蝇子草有单独的性别（雄性和雌性植物），并具有类似于哺乳动物的性染色体系统;雌性有两个X染色体，而雄性含有X和Y染色体。该物种的性别决定系统相对年轻，可能在1000万至1500万年前（MYA）进化，而哺乳动物的性别决定系统约为3.2亿年。性染色体仅在蝇子草属的少数物种中进化，这使我们能够比较具有和不具有性染色体的物种中染色体的结构和行为。这为研究导致性染色体进化的进化变化提供了一个独特的机会。我们想了解的两个问题是，性染色体是如何在campion中进化的，以及它们是如何成功地进行减数分裂的，因为X和Y染色体彼此之间存在很大的差异，因此在配对、联会和重组方面存在特定的问题。为此，我们将寻找与S.阔叶树性染色体这些探针在不同物种的性染色体（和性染色体同源染色体）上的位置将使用荧光原位杂交进行研究和比较，该方法允许将荧光标记的DNA探针与固定在载玻片上的染色体杂交。细胞分裂（减数分裂）期间性染色体的配对将使用荧光标记抗体进行研究，荧光标记抗体是特异性结合其他蛋白质的蛋白质，在我们的情况下，蛋白质参与染色体配对和重组。使用这些工具，我们将能够观察性染色体的配对和未配对区域作为染色体扩散上的荧光灶。比较Silene和哺乳动物的性染色体的结构和减数分裂行为将有助于了解减数分裂过程和控制是否以及在多大程度上在所有真核生物中是保守的。一个植物模型，如一个提供的Silene属是非常有利的，可能是有用的减数分裂的一般原则，因此在人类的生殖。