Genetic Control of Polar Nuclei Number in Maize Embryo Sacs

玉米胚囊极核数量的遗传控制

• 批准号: 0080353
• 负责人: Matthew Evans
• 金额: $ 30万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-08-15 至 2001-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0080353&HistoricalAwards=false
• 关键词: Genetic; Control; Polar; Nuclei; Number

0080353KermicleIn contrast to animals, the haploid products of meiosis do not differentiate into the gametes but undergo a few rounds of cell division to produce a multicellular gametophyte which produces the gametes. This is obvious in lower plants with large free-living gametophytes but is also the case in angiosperms, the gametophytes of which are highly reduced in size. Female gametophyte development in Arabidopisis and maize, begins when one of the products of meiosis undergoes three rounds of free nuclear division followed by cellularization to give rise to a seven celled embryo sac. The free nuclear divisions are invariant in number, tightly regulated as indicated by their synchrony, and accompanied by stereotypical nuclear migrations. The embryo sac consists of four cell types: the antipodal cells, the central cell, the synergids, and the egg. To further understand genetic regulation of female gametophyte development, mutants with excess polar nuclei in the central cell, which upon fertilization gives rise to the endosperm, are to be characterized in detail using maize as a model system. The sensitivity of maize endosperm development to the addition or subtraction of a single polar nucleus provides a sensitive screen for these mutants. These mutants are expected to affect one or both of two basic processes: nuclear positioning and partitioning or negative regulation of free nuclear divisions. Several mutants with excess polar nuclei have already been identified, and their characterization begun. The mechanism by which extra polar nuclei are produced in these mutants is to be determined by studying embryo sac ontogeny using confocal laser scanning microscopy. Interactions between the genes are to be determined by constructing double mutants between them. More mutants with extra polar nuclei are to be identified through genetic screens of existing mutant collections and collaborations with current genome projects. Molecular analysis of one of the best characterized of these genes, indeterminate gametophytel, is being initiated. A detailed analysis of these genes and their interactions should provide greater understanding of embryo sac development, particularly control of basic regulation of nuclear division and position.

与动物不同，减数分裂的单倍体产物不分化成配子，而是经过几轮细胞分裂产生多细胞配子体并产生配子。这在具有大量自由生长的配子体的低等植物中是明显的，但在被子植物中也是如此，其配子体的大小大大缩小。拟南芥和玉米的雌性配子体发育始于减数分裂的产物之一经过三轮自由核分裂，随后细胞化产生七个细胞的胚囊。自由核分裂在数量上是不变的，它们的同步性表明它们受到严格调控，并伴随着典型的核迁移。胚囊由四种细胞类型组成：对足细胞、中心细胞、协同细胞和卵。为了进一步了解雌性配子体发育的遗传调控，我们将以玉米为模型系统，对中心细胞中具有过量极核的突变体进行详细表征，这些极核在受精后产生胚乳。玉米胚乳发育对单极核增加或减少的敏感性为这些突变体提供了敏感的筛选。这些突变体预计会影响两个基本过程中的一个或两个：核定位和分裂或自由核分裂的负调控。已经确定了几个具有过量极核的突变体，并开始对其进行表征。在这些突变体中产生额外极核的机制将通过使用共聚焦激光扫描显微镜研究胚囊的个体发生来确定。基因之间的相互作用将通过在它们之间构建双突变体来确定。更多具有额外极核的突变体将通过现有突变体收集的基因筛选和与当前基因组计划的合作来确定。对这些基因中最具特征的不确定配子体的分子分析正在进行中。对这些基因及其相互作用的详细分析将有助于更好地理解胚囊的发育，特别是细胞核分裂和位置的基本调控。