PLANT EXPORTIN-T MUTATION DISRUPTS MERISTEM DEVELOPMENT

拟南芥暂停(PSD)基因的突变导致顶端分生组织中未分化的细胞死亡，叶片原基的产生延迟，以及叶片特性的异时性转变。PSD编码Exportin-t的同源基因，Exportin-t是成熟tRNA分子核输出所必需的基因。由于很少有Importin/Exportin家族的成员在多细胞生物体中具有特征，因此将采取几种方法来了解PSD在拟南芥发育中的作用。具体地说：1)PSD表达的空间和时间需求将由mRNA和蛋白质表达模式的特征以及PSD基因的靶向表达确定，2)遗传和分子分析将用于检测tRNA输出，并确定PSD突变对分生组织发育、叶片启动和相变相关基因的影响，以及3)将在筛选PSD表型的增强和抑制因子中分离潜在的下游因素。这些实验将为多能细胞的维持和分化以及发育“时钟”的调控提供洞察力。它们还将为在多细胞生物体发育过程中对核运输机械进行体内分析提供难得的机会。

Mutations in the Arabidopsis pauses (psd) gene result in the death of undifferentiated cells in the shoot apical meristem, a delay in the production of leaf primordial, and heterochronix shifts in leaf identity. PSD encodes a homologue of exportin-t, a gene required for the nuclear export of mature tRNA molecules. As very few members of the importin/ exportin family have been characterized in multi cellular organisms, several approaches will be taken to understand the role of PSD in Arabidosis development. Specifically: 1) the spatial and temporal requirements for PSD expression will be determined by characterization of the mRNA and protein expression patterns and by targeted expression of the PSD gene, 2) genetic and molecular analysis will be used to assay tRNA export and to determine the effect of the PSD mutation on genes involved in meristern development, leaf initiate, and phase change, and 3) potential downstream factors will be isolated in a screen for enhances and suppressors of the PSD phenotype. These experiments will offer insight into the maintenance and differentiation of pluripotent cells and the regulation of developmental 'clocks.' They will also provide a rare opportunity for the in vivo analysis of nuclear transport machinery during the development of a multi cellular organism.