How does ASYNAPSIS 5 mediate Synaptonemal Complex formation and crossover control in plants?

大多数开花植物（包括农作物）通过有性生殖繁殖，其中雄性配子（花粉）使雌性配子（胚珠）受精。配子包含双亲染色体数量的一半，在受精后恢复到正常水平。染色体的减半发生在减数分裂中，这是一种以同源重组为特征的特殊细胞分裂。同源重组打乱染色体片段，从而在子细胞中产生新的基因组合。因此，对植物育种者来说，在引进有利性状(如：产量)一起用于作物改良。提高作物基因洗牌效率的努力受到影响这一过程的内部制约；主要是重组水平及其倾向于定位于某些染色体区域，而在其他染色体区域很少发生。另外一个因素是许多农作物，如小麦、油菜和土豆都是多倍体，也就是说它们有多组相似或相同的染色体。然而，尽管这些植物已经适应了解决这一特殊问题，但它们仍然容易受到减数分裂失败的影响，从而导致不育。此外，由于全球变暖，该工艺对高温应力非常敏感，这是一个日益严峻的挑战。因此，了解减数分裂过程中的同源重组是如何在分子水平上控制的，将为未来的植物育种提供策略。我们已经确定了许多植物同源重组所必需的基因，但我们之前的分析预测了一个重要的未知基因的存在。我们现在已经在模式植物拟南芥中发现了该基因，并根据其表型将其命名为ASYNAPSIS5 （ASY5）。我们的初步数据表明，它是促进开花植物同源重组的基础基因。因此，本提案的目的是通过分子、细胞学、遗传和生化技术来表征ASY5蛋白的作用。我们将首先确定ASY5如何与已知的基因/蛋白质相互作用，然后量化ASY5如何在ASY5突变体中介导同源重组。接下来将研究ASY5如何稳定多倍体植物拟南芥的减数分裂，以及确定哪些基因变异在促进这一过程中更有效。最后，我们将确定拟南芥中ASY5的热敏性，以发现其在高温下失败的潜在分子机制，目的是识别更耐热的变异。

The majority of flowering plants (including crops) propagate through sexual reproduction where the male gamete (pollen) fertilises the female gamete (ovule). The gametes contain half the number of chromosomes of the parents that are restored to normal levels upon fertilisation. The halving of chromosomes occurs during meiosis, a specialised cell division characterised by homologous recombination. Homologous recombination shuffles segments of chromosomes, thus producing new combinations of genes in daughter cells. It is therefore a critical process for plant breeders in bringing advantageous traits (eg. yield) together for crop improvement. Efforts to increase the efficiency of gene shuffling in crops has been limited by internal constraints acting on this process; primarily the level of recombination and its tendency to be localized to certain chromosome regions and occur infrequently in others. An additional factor is many crop plants such as wheat, oil seed rape and potato are polyploids, that is they have multiple sets of chromosomes that are similar or identical. However, although such plants have adapted to solving this particular problem, they are still susceptible to meiotic failure that can yield in loss of fertility. In addition, this process is extremely sensitive to high temperature stress that is an increasing challenge due to global warming. Therefore, understanding how homologous recombination during meiosis is controlled at the molecular level will provide strategies for future-proofing plant breeding.We have already identified many of the genes essential for homologous recombination in plants, but our previous analysis predicted the existence of an essential unknown gene. We have now identified this gene in the model plant Arabidopsis thaliana and named it ASYNAPSIS5 (ASY5) based on its phenotype. Our preliminary data shows that it is a fundamental gene for promoting homologous recombination in flowering plants. Therefore, the aim of this proposal is to characterise the role of the ASY5 protein by molecular, cytological, genetical and biochemical techniques. We will first determine how ASY5 interacts with already known genes/proteins and then quantify how ASY5 mediates homologous recombination in asy5 mutants. This will be followed by an investigation into how ASY5 stabilises meiosis in the polyploid plant Arabidopsis lyrata as well as identifying which gene variants are more effective at promoting this process. Finally, we will determine the heat sensitivity of ASY5 in A. thaliana to discover the underlying molecular mechanism of why it fails at higher temperatures with the aim of identifying variants that are more heat tolerant.