Role of the Too Many Mouths Gene in the Regulation of Asymmetric Divisions and Stomatal Patterning

气孔由特殊的表皮细胞组成，它们调节光合作用的气体交换，对植物的生产力至关重要。它们也是研究不对称分裂在植物细胞命运规范和细胞模式中的作用的有价值的发育系统。在野生型植物中，气孔至少间隔一个细胞。这种间隔模式是在拟南芥中通过不对称分裂产生的，这种不对称分裂是通过明显的细胞间交流来确定分裂方向的，这些分裂是相对于先前存在的气孔或前体而言的。过多口（toomany mouth， TMM）突变在叶片中引起气孔簇，这是由于过度的不对称分裂导致的。这种表型表明TMM在参考或解释空间信息以正确定位和分配细胞命运决定因素方面起作用。与在叶片中发现的气孔集群相反，在其他器官（如茎）中减少了气孔的形成。这些相反的表型表明，TMM在几个不同水平上对气孔的产生和模式的形成起着关键作用。建议的工作重点是完成TMM基因的测序；其在野生型植物和气孔模式突变体中的表达谱测定其在转基因植物中的错表达效应分析图案化和错图案化的细胞学特征以及对茎中气孔形成如何被抑制的发育分析。长期目标是确定关键的命运决定因素以及参与气孔模式细胞信号传导的基因和事件。

Stomata consist of specialized epidermal cells that regulate gas exchangefor photosynthesis and are essential for plant productivity. They are alsoa valuable developmental system for studying the role of asymmetricdivisions in cell fate specification and in cell patterning in plants. Inwild-type plants, stomata are spaced at least one cell apart. This spacingpattern is generated in Arabidopsis through asymmetric divisions that areextrinsically referenced through apparent cell-cell communication to orientthose divisions with respect to a pre-existing stoma or precursor. The toomany mouths (TMM) mutation induces stomatal clusters in leaves that resultfrom excess asymmetric divisions that are often misoriented. Thisphenotype suggests that TMM functions in referencing or interpretingspatial information to correctly position and allocate cell fatedeterminants. In contrast to the stomatal clustering found in leaves, tmmeliminates the formation of stomata in other organs such as stems. Theseopposite phenotypes indicate that TMM plays a key role in stomatalproduction and patterning at several different levels. The work proposedfocuses on the completion of the sequencing of the TMM gene; thedetermination of its expression pattern in wild-type plants and in stomatalpatterning mutants; the analysis of the effects of its misexpression intransgenic plants; the characterization of the cytology of patterning andmispatterning; and a developmental analysis of how stomatal formation issuppressed in stems. Long term goals are to identify key fate determinantsand the genes and events involved in cell signaling in stomatal patterning.