NITROGEN LIMITATION ADAPTATION, a target of MicroRNA827, Mediates degradation of plasma membrane-localized phosphate transporters to maintain phosphate homeostasis in Arabidopsis
Journal
Plant Cell
Journal Volume
25
Journal Issue
10
Pages
4061-4074
Date Issued
2013
Author(s)
Abstract
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. © 2013 American Society of Plant Biologists.
Other Subjects
Arabidopsis protein; microRNA; MIRN827 microRNA, Arabidopsis; NLA protein, Arabidopsis; PHO2 protein, Arabidopsis; phosphate; phosphate transporter; plant RNA; ubiquitin conjugating enzyme; ubiquitin protein ligase
adaptation; Arabidopsis; cell membrane; cell vacuole; endocytosis; gene expression regulation; genetics; homeostasis; metabolism; protein degradation; ubiquitination
Type
journal article