Molecular Genetic Characterization of Epidermal Cell Interaction Mutants of Arabidopsis

Pruitt 97-23563 该研究项目的长期目标是阐明表皮细胞相互作用以及与花粉相互作用的分子机制。为此，已经对拟南芥地上器官异位融合突变体进行了全面的遗传分析。到目前为止，30个独立分离的突变导致这种fiddlehead（fdh）样表型已被映射和部分特征。这30个突变可以鉴定9个不同的互补组。 对fdh-1突变体的细胞学、生物化学和分子生物学特性的研究表明，fdh-1突变体植物与野生型植物的区别仅在于两个方面。第一，fdh-1植物表现出在粗壁（包括角质层）的脂质组成的变化，第二，表现出显着增强的壁渗透性相对于野生型植物。这些研究结果表明，在壁组成的差异可能是重要的调节反应的表皮与其他表皮细胞接触。除了这种接触介导的融合反应，fdh-l植物能够与花粉相互作用。此外，利用来自拟南芥和密切相关物种的花粉的实验揭示，花粉将在fdh-l枝条表面上萌发和生长，而来自水合缺陷突变体的花粉则不会。总之，这些数据表明，fdh-l植物表达的因子在地上部表面，不仅介导表皮细胞-细胞的相互作用，而且花粉识别和观察到的特异性与花粉的相互作用与野生型柱头乳突细胞的相似。 即将到来的研究阶段的目标是：1）完成该集合中融合突变体的遗传和表型表征，2）分离一些受影响的基因，3）筛选参与该发育途径调控的其他基因中的突变。

Pruitt 97-23563 The long term goal of this research project is to elucidate the molecular mechanisms by which epidermal cells interact with each other and with pollen. Toward this end a comprehensive genetic analysis of mutants showing ectopic fusion of above ground organs in Arabidopsis has been undertaken. To date 30 independently isolated mutations causing this fiddlehead (fdh)-like phenotype have been mapped and partially characterized. These 30 mutations putatively identify 9 different complementation groups. Cytological, biochemical and molecular characterization of the fdh-1 mutant demonstrated that fdh-l mutant plants differ from their wild-type counterparts in only two ways. First, fdh-1 plants exhibit changes in the lipid composition of the crude wall (including the cuticle), and second, exhibit markedly enhanced wall permeability relative to wild-type plants. These findings suggest that differences in wall composition may be important in regulating the responsiveness of the epidermis to contact with other epidermal cells. In addition to this contact-mediated fusion response, fdh-l plants are capable of interacting with pollen. Furthermore, experiments utilizing pollen from Arabidopsis and closely related species reveal that pollen will germinate and grow on the fdh-l shoot surface whereas pollen from hydration-defective mutants will not. Taken together these data suggest that fdh-l plants express factors on the shoot surface that mediate not only epidermal cell-cell interactions but also pollen recognition and that the observed specificity of the interaction with pollen parallels that of wild-type stigmatic papillar cells. The objectives for the upcoming research period are: 1) to complete the genetic and phenotypic characterization of the fusion mutants in this collection, 2) to isolate some of the affected genes and 3) to screen for mutations in other genes involved in the regulation of this developmental pathway.