ESCRT-III-Associated Protein ALIX Mediates High-Affinity Phosphate Transporter Trafficking to Maintain Phosphate Homeostasis in Arabidopsis.
Prior to the release of their cargoes into the vacuolar lumen, sorting endosomes mature into multivesicular bodies (MVBs) through the action of ENDOSOMAL COMPLEX REQUIRED FOR TRANSPORT (ESCRT) protein complexes. MVB-mediated sorting of high-affinity phosphate transporters (PHT1) to the vacuole limits their plasma membrane levels under phosphate-sufficient conditions, a process that allows plants to maintain phosphate homeostasis. Here, we describe ALIX, a cytosolic protein that associates with MVB by interacting with ESCRT-III subunit SNF7 and mediates PHT1;1 trafficking to the vacuole in Arabidopsis thaliana. We show that the partial loss-of-function mutant alix-1 displays reduced vacuolar degradation of PHT1;1. ALIX derivatives containing the alix-1 mutation showed reduced interaction with SNF7, providing a simple molecular explanation for impaired cargo trafficking in alix-1 mutants. In fact, the alix-1 mutation also hampered vacuolar sorting of the brassinosteroid receptor BRI1. We also show that alix-1 displays altered vacuole morphogenesis, implying a new role for ALIX proteins in vacuolar biogenesis, likely acting as part of ESCRT-III complexes. In line with a presumed broad target spectrum, the alix-1 mutation is pleiotropic, leading to reduced plant growth and late flowering, with stronger alix mutations being lethal, indicating that ALIX participates in diverse processes in plants essential for their life.
Centro Nacional de Biotecnología (CNB-CSIC) Darwin, 28049 Madrid, Spain.
Ximena
X
Cardona-López
Centro Nacional de Biotecnología (CNB-CSIC) Darwin, 28049 Madrid, Spain Unité Mixte de Recherche 6191, Centre National de la Recherche Scientifique-Commissariat à l'Energie Atomique, Aix-Marseille II, F-13108 Saint-Paul-lès-Durance Cedex, France.
Laura
L
Cuyas
Unité Mixte de Recherche 6191, Centre National de la Recherche Scientifique-Commissariat à l'Energie Atomique, Aix-Marseille II, F-13108 Saint-Paul-lès-Durance Cedex, France.
Elena
E
Marín
Centro Nacional de Biotecnología (CNB-CSIC) Darwin, 28049 Madrid, Spain.
Charukesi
http://orcid.org/0000-0003-2780-4888
C
Rajulu
Centro Nacional de Biotecnología (CNB-CSIC) Darwin, 28049 Madrid, Spain.
María Luisa
ML
Irigoyen
Centro Nacional de Biotecnología (CNB-CSIC) Darwin, 28049 Madrid, Spain.
Erica
E
Gil
Centro Nacional de Biotecnología (CNB-CSIC) Darwin, 28049 Madrid, Spain.
María Isabel
MI
Puga
Laboratoire de Physiologie Cellulaire Vegetale, Unité Mixte de Recherche 5168, Institut de Recherche en Technologie et Sciences pour le Vivant, CEA, Grenoble Cedex 9, France.
Richard
R
Bligny
Unité Mixte de Recherche 6191, Centre National de la Recherche Scientifique-Commissariat à l'Energie Atomique, Aix-Marseille II, F-13108 Saint-Paul-lès-Durance Cedex, France.
Laurent
L
Nussaume
Department of Plant Molecular Biology, University of Lausanne, UNIL-Sorge, 1015 Lausanne, Switzerland.
Niko
N
Geldner
Centro Nacional de Biotecnología (CNB-CSIC) Darwin, 28049 Madrid, Spain jpazares@cnb.csic.es vrubio@cnb.csic.es.
Javier
J
Paz-Ares
Centro Nacional de Biotecnología (CNB-CSIC) Darwin, 28049 Madrid, Spain jpazares@cnb.csic.es vrubio@cnb.csic.es.
Vicente
http://orcid.org/0000-0002-8800-2400
V
Rubio
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D056827:Endosomal Sorting Complexes Required for Transport / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D049452:Green Fluorescent Proteins / Q000235:genetics; D006706:Homeostasis; D009154:Mutation; D028061:Phosphate Transport Proteins / Q000235:genetics / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D055503:Protein Multimerization; D021381:Protein Transport; D014617:Vacuoles / Q000235:genetics / Q000378:metabolism
C000606499:ALIX protein, Arabidopsis; D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D056827:Endosomal Sorting Complexes Required for Transport; C520845:PHT1;1 protein, Arabidopsis; D028061:Phosphate Transport Proteins; D010710:Phosphates; D049452:Green Fluorescent Proteins; D011494:Protein Kinases; C108270:BRI1 protein, Arabidopsis