A developmental framework for endodermal differentiation and polarity
A developmental framework for endodermal differentiation and polarity
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DOI：
10.1073/pnas.0910772107
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发表时间：
2010-03-16
影响因子：
11.1
通讯作者：
Geldner, Niko
中科院分区：
文献类型：
--
作者：
Alassimone, Julien;Naseer, Sadaf;Geldner, Niko
内皮层是高等植物常见的根细胞层，对根的功能和养分吸收至关重要。内皮层通过其凯氏带将外部（外围）和内部（中心）细胞层分开，凯氏带是精确排列的特化壁材料带。在这里，我们揭示了在凯氏带的膜是质膜的中心和周边区域之间的扩散屏障，它介导的附着到细胞外基质。因此，这个膜区域的功能类似于动物上皮细胞中的紧密连接，尽管植物缺乏在动物中建立紧密连接的分子模块。我们还确定了一对流入和流出转运蛋白，标志着中央和外周领域的质膜。这些转运蛋白在分生组织中已经显示出相反的极性分布，但它们的定位在分化时变得精细和受限。这种“中心-外周”极性与PIN蛋白定义的顶端-基底极性共存于同一细胞内，但利用不同的极性决定子。在早期胚胎发生中已经可以观察到中央-外周极性，其中它揭示了静止中心前体细胞内的细胞极性。极性结构域之间的严格扩散阻滞在动物中很常见，但从未在植物中描述过。然而，它与内胚层功能的相关性是显而易见的，因为内胚层的中央和外周膜面对根本不同的根室。深入研究植物根内皮层转运蛋白的极性及其屏障功能，将有助于我们对植物根营养和抗逆性的认识。
The endodermis is a root cell layer common to higher plants and of fundamental importance for root function and nutrient uptake. The endodermis separates outer (peripheral) from inner (central) cell layers by virtue of its Casparian strips, precisely aligned bands of specialized wall material. Here we reveal that the membrane at the Casparian strip is a diffusional barrier between the central and peripheral regions of the plasma membrane and that it mediates attachment to the extracellular matrix. This membrane region thus functions like a tight junction in animal epithelia, although plants lack the molecular modules that establish tight junction in animals. We have also identified a pair of influx and efflux transporters that mark both central and peripheral domains of the plasma membrane. These transporters show opposite polar distributions already in meristems, but their localization becomes refined and restricted upon differentiation. This "central-peripheral" polarity coexists with the apical-basal polarity defined by PIN proteins within the same cells, but utilizes different polarity determinants. Central-peripheral polarity can be already observed in early embryogenesis, where it reveals a cellular polarity within the quiescent center precursor cell. A strict diffusion block between polar domains is common in animals, but had never been described in plants. Yet, its relevance to endodermal function is evident, as central and peripheral membranes of the endodermis face fundamentally different root compartments. Further analysis of endodermal transporter polarity and manipulation of its barrier function will greatly promote our understanding of plant nutrition and stress tolerance in roots.