Molecular and Developmental Studies of a Shootless Mutant of Maize

9318447 Rivin博士分离出一种玉米突变体，命名为dks8（缺陷核无芽mu8），它破坏了芽分生组织功能的早期建立，但不干扰子叶和主根的正常形态发生和分化。这些特征在玉米胚突变体中是独一无二的，它们表明dks8突变所鉴定的基因在胚茎形成的一个基本步骤中是必需的。通过研究该基因在胚胎发育中的作用，确定其是否在胚胎后发育中起作用，并确定其序列和产物，可以确定对植物发育至关重要的细胞过程之一。该研究项目有以下目标：1)利用EMS诱变和Mutator转座子进行定向诱变，从现有的突变体收集中鉴定dks8的其他等位基因。2)利用Mutator转座子标签克隆并定位Dks8基因。dks8突变似乎是由罗伯逊突变子转座系统的Mu8元素的插入引起的。该元件两侧的序列将被克隆并用于绘制dks8位点。将对它们进行分析，以发现这种对发育至关重要的基因的产物。3)确定dks8突变如何以及何时阻止胚芽发育。组织学和分子标准将用于测试dks8突变体的茎尖分生组织细胞群体是否在胚胎发生的第一阶段被启动和维持。体细胞胚胎发生和胚乳基因型的操作将用于研究dks8基因的作用是发育中的胚胎所固有的，还是作为大胚珠或种子环境的一部分。4)确定Dks8基因产物在胚胎发生之外是否需要用于茎尖分生组织的规范或功能。细胞系克隆分析将用于确定dks8基因型e对已建立的茎尖分生组织中细胞发育命运的影响。＊＊＊

9318447 Rivin Dr. Rivin has isolated a maize mutant, termed, dks8 (defective kernel shootless-Mu8), that disrupts the early establishment of a functional shoot meristem, but does not perturb the normal morphogenesis and differentiation of the cotyledon and primary root. These features are unique among the embryo mutants of maize, and they indicate that the gene identified by the dks8 mutation is required for a fundamental step in the formation of the embryonic shoot. By examining the role of this gene during embryonic development, determining if it plays part in post-embryonic development, and identifying its sequence and product, one of the cellular processes critical to plant development may be defined. The research program has the following objectives: 1) Identify other alleles of dks8 from existing mutant collections and by targeted mutagenesis using EMS- mutagenized and Mutator transposon stocks. 2) Clone and map the Dks8 gene using the Mutator transposon tag. The dks8 mutation appears to have been caused by the insertion of a Mu8 element of the Robertson's Mutator transposable system. The sequences flanking this element will be cloned and used to map the dks8 locus. They will be analyzed to discover the product of this developmentally important gene. 3) Determine how and when the dks8 mutation prevents embryonic shoot development. Histological and molecular criteria will be used to test whether the shoot apical meristem cell population is initiated and maintained in the first stages of embryogenesis in dks8 mutants. Somatic embryogenesis and manipulation of endosperm genotype will be used to examine whether dks8 gene action is intrinsic to the developing embryo or whether it acts as part of the larger ovule or seed environment. 4) Determine it the Dks8 gene product is required outside of embryogenesis for the specification or function of the shoot apical meristem. Clonal analysis of cell lineage will be used to determine the effect of the dks8 genotyp e on the developmental fate of cells in an established shoot apical meristem. ***