Auxin-mediated root branching is determined by the form of available nitrogen
Auxin-mediated root branching is determined by the form of available nitrogen
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DOI：
10.1038/s41477-020-00756-2
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发表时间：
2020-09-01
期刊：
影响因子：
18
通讯作者：
von Wiren, Nicolaus
中科院分区：
文献类型：
--
作者：
Meier, Markus;Liu, Ying;von Wiren, Nicolaus
铵态氮和硝态氮是土壤中无机氮的两种主要形态。铵通过触发侧根分枝来塑造植物的根结构。在这里，研究人员研究了质子化生长素进入覆盖侧根原基的皮层和表皮细胞的pH依赖性机制。为了改善从土壤中获得的水分和养分，植物可以调节它们的根系结构。尽管重要的根结构的变化，利用当地的营养补丁发生在异质性土壤或施肥后，机制整合外部营养信号到根发育计划仍然知之甚少。在这里，我们表明，本地铵供应刺激积累的地上部衍生的生长素在根脉管系统，促进侧根出现，建立一个高度分支的根系。pH值和生长素报告的活动表明，铵转运介导的铵吸收酸化根质外体，这增加了pH值依赖进口的质子化生长素到皮层和表皮细胞覆盖侧根原基，随后促进他们出现从父母根。因此，铵诱导和H+-ATP酶介导的质外体酸化允许生长素绕过生长素进口商AUX 1和LAX 3。在缺氮植物中，生长素也在根维管系统中积累，但碱性更强的质外体导致生长素保留在这些组织中并阻止侧根形成。我们的研究强调了外部可用氮的形式对pH依赖的放射状生长素的流动性及其在器官发育中的调节功能的影响。
Ammonium and nitrate are the two major forms of inorganic nitrogen in soils. Ammonium shapes root architecture of plants by triggering lateral root branching. Here the researchers investigated the mechanism involving pH-dependent import of protonated auxin into the cortical and epidermal cells overlaying lateral root primordia.To improve water and nutrient acquisition from the soil, plants can modulate their root system architecture. Despite the importance of changes in root architecture to exploit local nutrient patches occurring in heterogenous soils or after placed fertilization, mechanisms integrating external nutrient signals into the root developmental programme remain poorly understood. Here, we show that local ammonium supply stimulates the accumulation of shoot-derived auxin in the root vasculature and promotes lateral root emergence to build a highly branched root system. Activities of pH and auxin reporters indicate that ammonium uptake mediated by ammonium transporters acidifies the root apoplast, which increases pH-dependent import of protonated auxin into cortical and epidermal cells overlaying lateral root primordia, and subsequently promotes their emergence from the parental root. Thereby, ammonium-induced and H+-ATPase-mediated acidification of the apoplast allows auxin to bypass the auxin importers AUX1 and LAX3. In nitrogen-deficient plants, auxin also accumulates in the root vasculature but a more alkaline apoplast leads to retention of auxin in these tissues and prevents lateral root formation. Our study highlights the impact of externally available nitrogen forms on pH-dependent radial auxin mobility and its regulatory function in organ development.