Pillitteri Lynn Jo, Bogenschutz Naomi L, Torii Keiko U
Department of Biology, University of Washington, Seattle, WA 98195, USA.
Plant Cell Physiol. 2008 Jun;49(6):934-43. doi: 10.1093/pcp/pcn067. Epub 2008 May 1.
Stomata are turgor-driven epidermal valves on the surface of plants that allow for efficient gas and water exchange between the plant and its environment. The Arabidopsis thaliana basic helix-loop-helix (bHLH) protein, MUTE, is a master regulator of stomatal differentiation where it is required for progression through the stomatal lineage and the differentiation of stomata. The genetic control of stomatal spacing across the epidermal surface is variable in different organs. For instance, a distinct suite of genes from those in leaves regulates stomatal patterning in hypocotyls. Here we report that regardless of organ type, MUTE controls downstream events directing stomatal differentiation, specifically the transition from meristemoid to guard mother cell. Ectopic MUTE expression is sufficient to over-ride cell fate specification in cell types that do not normally differentiate stomata. Furthermore, MUTE is required for the production of the structure evolutionarily related to stomata, the hydathode pore. Consistently, MUTE displays expression at the tip of cotyledons and leaves, thus co-localizing with the auxin maxima. However, MUTE itself was not regulated by the auxin, and the absence of hydathode pores in mute did not affect the auxin maxima. Surprisingly, our analysis revealed that the requirement for MUTE could be partially circumvented under conditions of compromised inhibitory signaling.
气孔是植物表面由膨压驱动的表皮瓣膜，可实现植物与其环境之间高效的气体和水分交换。拟南芥基本螺旋-环-螺旋（bHLH）蛋白MUTE是气孔分化的主要调节因子，在气孔谱系进展和气孔分化过程中发挥作用。不同器官中表皮表面气孔间距的遗传控制存在差异。例如，与叶片中不同的一组特定基因调控下胚轴中的气孔模式。我们在此报告，无论器官类型如何，MUTE都控制着指导气孔分化的下游事件，特别是从分生细胞到保卫母细胞的转变。异位表达MUTE足以改变通常不会分化出气孔的细胞类型中的细胞命运决定。此外，与气孔在进化上相关的结构——水孔的产生也需要MUTE。一致的是，MUTE在子叶和叶片尖端表达，因此与生长素最大值共定位。然而，MUTE本身不受生长素调控，且mute突变体中没有水孔并不影响生长素最大值。令人惊讶的是，我们的分析表明，在抑制信号受损的条件下，对MUTE的需求可以部分得到规避。
