Root zone-specific localization of AMTs determines ammonium transport pathways and nitrogen allocation to shoots.
Root zone-specific localization of AMTs determines ammonium transport pathways and nitrogen allocation to shoots.
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DOI：
10.1371/journal.pbio.2006024
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发表时间：
2018-10
期刊：
影响因子：
9.8
通讯作者：
von Wirén N
中科院分区：
文献类型：
--
作者：
Duan F;Giehl RFH;Geldner N;Salt DE;von Wirén N
在植物中，芽的营养供应取决于营养物质的吸收和通过根组织向维管系统的运输。通过质外体运输途径（ATP）或通过共质体运输途径（STP）将营养物递送至脉管系统，所述ATP利用细胞壁中的自由空间并且由内皮层处的质外体屏障和营养物转运蛋白控制。然而，这些运输路线的相对重要性仍然难以捉摸。在这里，我们表明，STP，介导的表皮铵转运蛋白1;3（AMT 1;3），占主导地位的径向运动铵在整个根组织时，外部铵低，而质外体运输控制的AMT 1;2在内皮盛行在高外部铵。其次，AMT 1;2有利于氮（N）分配到地上部，揭示了ATP对营养分配到地上部的重要性。当通过废除凯氏带（CS）形成引入内胚层旁路时，质外体铵转运减少。相比之下，共质体运输增加，表明STP和内胚层旁路之间的协同作用。我们进一步确定，质外体屏障的形成改变了细胞类型特异性定位的AMT和确定STP和ATP的贡献。这些结果表明，径向运输途径如何变化沿着纵向梯度的根轴，并有助于根和芽之间的养分分配。营养物质从土壤向植物根系维管系统的径向运输是通过共质体运输途径（STP）和质外体运输途径（ATP）进行的。营养物质在穿过外细胞的质膜并通过由胞间连丝形成的细胞质连续体向木质部移动时，沿着STP移动。ATP之后的营养物质最初被动地通过细胞外间隙移动，但最终被内胚层细胞吸收，其中凯氏带（CS）阻止进一步的质外体移动。我们通过在CS缺陷突变体中表达细胞类型特异性铵转运蛋白，评估了这些转运途径对根径向运输和营养供应的贡献。我们的研究表明，i）共质体运输在低外部铵供应更有效; ii）当内胚层细胞被木栓质薄层沉积封闭时，铵转运蛋白的表达转移到皮层细胞; iii）质外体运输依赖于内胚层的功能性质外体屏障，有利于氮（N）分配到高外部铵的芽。
In plants, nutrient provision of shoots depends on the uptake and transport of nutrients across the root tissue to the vascular system. Nutrient delivery to the vasculature is mediated via the apoplastic transport pathway (ATP), which uses the free space in the cell walls and is controlled by apoplastic barriers and nutrient transporters at the endodermis, or via the symplastic transport pathway (STP). However, the relative importance of these transport routes remains elusive. Here, we show that the STP, mediated by the epidermal ammonium transporter 1;3 (AMT1;3), dominates the radial movement of ammonium across the root tissue when external ammonium is low, whereas apoplastic transport controlled by AMT1;2 at the endodermis prevails at high external ammonium. Then, AMT1;2 favors nitrogen (N) allocation to the shoot, revealing a major importance of the ATP for nutrient partitioning to shoots. When an endodermal bypass was introduced by abolishing Casparian strip (CS) formation, apoplastic ammonium transport decreased. By contrast, symplastic transport was increased, indicating synergism between the STP and the endodermal bypass. We further establish that the formation of apoplastic barriers alters the cell type–specific localization of AMTs and determines STP and ATP contributions. These results show how radial transport pathways vary along the longitudinal gradient of the root axis and contribute to nutrient partitioning between roots and shoots. Radial transport of nutrients from the soil to the vascular system of plant roots occurs via the symplastic transport pathway (STP) and apoplastic transport pathway (ATP). Nutrients move along the STP when crossing the plasma membrane of outer cells and moving to xylem through the cytoplasmic continuum formed by plasmodesmata. Nutrients following the ATP, in turn, initially move passively through the extracellular space but are eventually taken up by endodermal cells, in which Casparian strips (CSs) prevent further apoplastic movement. We assessed the contribution of these transport pathways to radial transport in roots and nutrient provision to shoots by expressing cell type–specific ammonium transporters in a CS-defective mutant. Our study reveals that i) symplastic transport is more efficient at low external ammonium supply; ii) when endodermal cells become sealed by the deposition of suberin lamellae, the expression of ammonium transporters shifts to cortical cells; and iii) apoplastic transport depends on a functional apoplastic barrier at the endodermis, favoring nitrogen (N) partitioning to shoots at high external ammonium.
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影响因子：
7.7
作者：
Pfister A;Barberon M;Alassimone J;Kalmbach L;Lee Y;Vermeer JE;Yamazaki M;Li G;Maurel C;Takano J;Kamiya T;Salt DE;Roppolo D;Geldner N
通讯作者：
Geldner N
影响因子：
7.4
作者：
Giehl, Ricardo F. H.;von Wiren, Nicolaus
通讯作者：
von Wiren, Nicolaus
影响因子：
7.4
作者：
Loqué, D;Ludewig, U;von Wirén, N
通讯作者：
von Wirén, N
DOI：
10.1073/pnas.0910772107
发表时间：
2010-03-16
影响因子：
11.1
作者：
Alassimone, Julien;Naseer, Sadaf;Geldner, Niko
通讯作者：
Geldner, Niko
影响因子：
56.9
作者：
Doblas, Veronica G.;Smakowska-Luzan, Elwira;Geldner, Niko
通讯作者：
Geldner, Niko