Molecular Genetic Characterization of Epidermal Cell Interaction Mutants of Arabidopsis

Pruitt 97-23563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，已经有30个独立分离的突变导致了这种鞭毛虫(FDH)样的表型，并对其进行了部分表征。这30个突变可能识别9个不同的互补组。对突变株的细胞学、生化和分子鉴定表明，突变株FDH-L与野生型植株只有两个方面的不同。首先，FDH-1植物的粗壁(包括角质层)的脂质成分发生了变化，其次，相对于野生型植物，FDH-1植物的壁透性显著增强。这些发现表明，壁成分的差异在调节表皮与其他表皮细胞接触的反应性方面可能是重要的。除了这种接触介导的融合反应，外源脱氢酶-L植物还能够与花粉相互作用。此外，利用拟南芥和近缘物种的花粉进行的实验表明，花粉可以在FDH-L的芽面上萌发和生长，而来自水合缺陷突变体的花粉不会。综上所述，这些数据表明，外源脱氢酶-L植物在茎表面表达不仅介导表皮细胞-细胞相互作用的因子，而且与花粉相互作用的观察到的特异性与野生型柱头乳头细胞相似。即将到来的研究阶段的目标是：1)完成这个集合中融合突变体的遗传和表型特征，2)分离一些受影响的基因，3)筛选参与调节这一发育途径的其他基因的突变。

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.