Multiple mechanisms of nitrate sensing by Arabidopsis nitrate transceptor NRT1.1
Multiple mechanisms of nitrate sensing by Arabidopsis nitrate transceptor NRT1.1
复制标题
DOI：
10.1038/nplants.2015.15
复制
发表时间：
2015-03-02
期刊：
影响因子：
18
通讯作者：
Gojon, A.
中科院分区：
文献类型：
--
作者：
Bouguyon, E.;Brun, F.;Gojon, A.
在拟南芥中，质膜硝酸盐转运体(转运体/受体)NRT1.1调控许多对硝酸盐的生理和发育反应。在促进硝酸盐吸收的同时，NRT1.1还调节许多硝酸盐同化途径基因的表达水平，调节根系构型，解除种子休眠，保护植物免受铵毒害。在这里，我们评估了NRT1.1的两个关键残基(P492和T101)的点突变对功能和表型的影响。我们发现，这些点突变不同地影响了NRT1.1依赖的几个对硝酸盐的反应，即在低硝酸盐浓度下抑制侧根发育，以及在高硝酸盐浓度下短期上调硝酸盐吸收基因NRT2.1及其长期下调。我们还表明，这些突变对全基因组的基因表达有不同的影响。我们的发现表明，NRT1.1激活了四个独立的信号机制，这四个机制在蛋白质中具有独立的结构基础。特别是，我们提出的证据表明，在T101的NRT1.1的磷酸化和非磷酸化形式具有不同的信号功能，并且依赖于硝酸盐对根发育的调控依赖于磷酸化形式。我们的发现进一步证明，NRT1.1能够在拟南芥中触发独立的信号通路，以响应不同的环境条件。
In Arabidopsis the plasma membrane nitrate transceptor (transporter/receptor) NRT1.1 governs many physiological and developmental responses to nitrate. Alongside facilitating nitrate uptake, NRT1.1 regulates the expression levels of many nitrate assimilation pathway genes, modulates root system architecture, relieves seed dormancy and protects plants from ammonium toxicity. Here, we assess the functional and phenotypic consequences of point mutations in two key residues of NRT1.1 (P492 and T101). We show that the point mutations differentially affect several of the NRT1.1-dependent responses to nitrate, namely the repression of lateral root development at low nitrate concentrations, and the short-term upregulation of the nitrate-uptake gene NRT2.1, and its longer-term downregulation, at high nitrate concentrations. We also show that these mutations have differential effects on genome-wide gene expression. Our findings indicate that NRT1.1 activates four separate signalling mechanisms, which have independent structural bases in the protein. In particular, we present evidence to suggest that the phosphorylated and non-phosphorylated forms of NRT1.1 at T101 have distinct signalling functions, and that the nitrate-dependent regulation of root development depends on the phosphorylated form. Our findings add to the evidence that NRT1.1 is able to trigger independent signalling pathways in Arabidopsis in response to different environmental conditions.