NITROGEN LIMITATION ADAPTATION, a Target of MicroRNA827, Mediates Degradation of Plasma Membrane-Localized Phosphate Transporters to Maintain Phosphate Homeostasis in Arabidopsis
NITROGEN LIMITATION ADAPTATION, a Target of MicroRNA827, Mediates Degradation of Plasma Membrane-Localized Phosphate Transporters to Maintain Phosphate Homeostasis in Arabidopsis
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DOI：
10.1105/tpc.113.116012
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发表时间：
2013-10-01
期刊：
影响因子：
11.6
通讯作者：
Chiou, Tzyy-Jen
中科院分区：
文献类型：
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作者：
Lin, Wei-Yi;Huang, Teng-Kuei;Chiou, Tzyy-Jen
拟南芥磷酸转运蛋白1(PHT1)家族成员是从根际获取磷的关键成员，它们的调控对于维持细胞磷的动态平衡是必不可少的。在这里，我们通过环型泛素E3连接酶，氮限制适应(NLA)调节PHT1蛋白的降解，揭示了PI转运的翻译后调节。NLA功能的丧失导致了高PI的积累，这是由于几个PHT1在蛋白质水平而不是在转录水平上的水平增加所致。NLA突变体中PHT1的内吞作用和泛素化减少，以及质膜上NLA和PHT1之间的相互作用表明，NLA指导质膜上定位的PHT1的泛素化，从而触发依赖于笼蛋白的内吞作用，随后内体对空泡进行分选。此外，NLA和PHOSPHATE2(PHO2；一种泛素E2结合酶)在亚细胞内的不同定位以及PHT1和PI在NLA Pho2突变体中积累的协同效应表明，它们独立但协同地调节PHT1蛋白的数量。有趣的是，NLA和PHO2分别是PI饥饿诱导的两个microRNAs miR827和miR399的靶标。因此，我们的发现揭示了通过整合microRNA介导的转录后途径和泛素介导的翻译后调控途径来调节PI转运活性以响应PI的可用性。
Members of the Arabidopsis thaliana PHOSPHATE TRANSPORTER1 (PHT1) family are key players in acquisition of Pi from the rhizosphere, and their regulation is indispensable for the maintenance of cellular Pi homeostasis. Here, we reveal posttranslational regulation of Pi transport through modulation of degradation of PHT1 proteins by the RING-type ubiquitin E3 ligase, NITROGEN LIMITATION ADAPTATION (NLA). Loss of function of NLA caused high Pi accumulation resulting from increases in the levels of several PHT1s at the protein rather than the transcript level. Evidence of decreased endocytosis and ubiquitination of PHT1s in nla mutants and interaction between NLA and PHT1s in the plasma membranes suggests that NLA directs the ubiquitination of plasma membrane-localized PHT1s, which triggers clathrin-dependent endocytosis followed by endosomal sorting to vacuoles. Furthermore, different subcellular localization of NLA and PHOSPHATE2 (PHO2; a ubiquitin E2 conjugase) and the synergistic effect of the accumulation of PHT1s and Pi in nla pho2 mutants suggest that they function independently but cooperatively to regulate PHT1 protein amounts. Intriguingly, NLA and PHO2 are the targets of two Pi starvation-induced microRNAs, miR827 and miR399, respectively. Therefore, our findings uncover modulation of Pi transport activity in response to Pi availability through the integration of a microRNA-mediated posttranscriptional pathway and a ubiquitin-mediated posttranslational regulatory pathway.