CYTOGENETICS OF MEIOSIS OF MAIZE

我们的目标是了解减数分裂过程中染色体分离的机制，特别是同源染色体如何配对和突触。玉米雄性微核细胞是唯一一个存在大量影响减数分裂的突变体的系统，因此有可能进行极好的细胞学研究。我们使用荧光原位杂交(FISH)探针和抗RAD51抗体在去卷积光学显微镜系统上收集了3D图像，以描述在同源性搜索过程中端粒、染色体和重组机制的重排。没有同系物的减数分裂前联系；相反，同源染色体在细线末端彼此接近，因为端粒与核膜(NE)和簇(花束形成)相联系。当配对开始时，我们将使用FISH探针来照亮一个特定染色体臂上的多个斑点，FISH着丝粒特异探针，以及针对重组机制的抗体(RAD51，MSH2/6)来分析3D同源比对。分析缺乏突触的染色体衍生品的配对行为，如环、缺失杂合子、双着丝粒和相互易位，将使我们能够测试对染色体末端、端粒序列和亚端粒或内部同源性的要求，以成功配对。我们将分析在同源性搜索的早期阶段(AfD，dsy1)或后期阶段(as1，dy1，dsy2等)已知有缺陷的突变体的染色体配对行为。我们正在开发基于部分花粉败育或改变的重组率的新型筛选，以寻找新的减数分裂突变。我们正在使用定向转座子标签来克隆新的突变体或现有的配对有缺陷的突变体。我们假设同源搜索依赖于端粒-NE联合介导的染色体的活跃运动。我们将使用大块异染色质(旋钮)作为标记来分析活的微核细胞中的同源比对和端粒聚集。秋水仙碱在体外阻断端粒与NE的相互作用。我们将分析秋水仙碱如何扰乱核组织的其他方面，如核孔分布。减数分裂对所有有性生殖生物体都是必不可少的，这里描述的研究将进一步加深我们对这一过程的理解，不仅在玉米中，而且在所有生物体中。减数分裂的机制是一个重要的医学问题，减数分裂过程中不准确的染色体分离(非整倍体)在几种先天性畸形中是偶然的，这是人类过早终止妊娠和配子产生不良的主要原因。

Our goal is to understand the mechanism of chromosome segregation during meiosis, particularly how homologous chromosomes pair and synapse. The maize male meiocyte is the only system where there is a large collection of mutants that affect meiosis, and it is possible to do superb cytology. We have collected 3-D images on a deconvolution light microscope system using fluorescence in situ hybridization (FISH) probes and antibodies against RAD51 to describe the rearrangements of telomeres, chromosomes and the recombination machinery during the homology search. There is no premeiotic association of homologs; rather, homologous chromosomes approach each other at the end of leptotene as telomeres associate with the nuclear envelope (NE) and cluster (bouqet formation). We will use FISH probes which light up multiple spots on one specific chromosome arm, FISH centromere specific probes, and antibodies against the recombination machinery (RAD51, MSH2/6) to analyze in 3-D homolog alignment as pairing is initiated. Analysis of the pairing behavior of chromosomal derivatives deficient in synapsis such as rings, deficiency heterozygotes, ditelocentrics and reciprocal translocations will allow us to test the requirements for chromosome ends, telomeric sequences, and subtelomeric or internal homology, for successful pairing. We will analyze the pairing behavior of chromosomes in mutants known to be deficient in the early stages of the homology search (afd, dsy1) or in later stages (as1, dy1, dsy2, etc.). We are developing novel screens based on partial pollen abortion or altered recombination rates to find new meiotic mutants. We are using directed transposon tagging to clone new mutants or existing mutants which are defective in pairing. We assume that the homology search is dependent on the active movement of chromosomes, mediated by telomere-NE associations. We will analyze homolog alignment and telomere clustering in living meiocytes using large blocks of heterochromatin (knobs) as markers. Colchicine blocks telomere interactions with the NE in vitro. We will analyze how colchicine disrupts other aspects on nuclear organization such as nuclear pore distribution. Meiosis is essential for all sexually reproducing organisms and the studies described here will further our understanding of this process not only in maize but in all organisms. The mechanism of meiosis is a topic of major medical interest inaccurate chromosome segregation (aneuploidy) during meiosis is casual in several congenital malformations, a major cause of premature termination of pregnancy, and of poor gamete production in humans.