Molecular Genetic Characterization of Epidermal Cell Interaction Mutants of Arabidopsis

本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，对拟南芥地上器官异位融合的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了这种fidlehead （fdh）样表型已经被绘制和部分表征。这30个突变被推测为9个不同的互补群。fdh-1突变体的细胞学、生化和分子特征表明，fdh-1突变体植株与野生型植株只有两个不同之处。首先，fdh-1植物的粗壁（包括角质层）的脂质组成发生了变化；其次，相对于野生型植物，fdh-1植物的壁通透性明显增强。这些发现表明，壁组成的差异可能在调节表皮与其他表皮细胞接触的反应性方面很重要。除了这种接触介导的融合反应外，fdh- 1植物还能够与花粉相互作用。此外，利用拟南芥及其近缘种的花粉进行的实验表明，花粉可以在fdh- 1茎表面萌发和生长，而来自水化缺陷突变体的花粉则不能。综上所述，这些数据表明，fdh- 1植物在茎表面表达的因子不仅介导表皮细胞间的相互作用，还介导花粉识别，并且观察到与花粉相互作用的特异性与野生型柱头乳头细胞相似。接下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.