title: Inter-regulation of the unfolded protein response and auxin signaling.
abstract: The unfolded protein response (UPR) is a signaling network triggered by overload of protein-folding demand in the endoplasmic reticulum (ER), a condition termed ER stress. The UPR is critical for growth and development; nonetheless, connections between the UPR and other cellular regulatory processes remain largely unknown. Here, we identify a link between the UPR and the phytohormone auxin, a master regulator of plant physiology. We show that ER stress triggers down-regulation of auxin receptors and transporters in Arabidopsis thaliana. We also demonstrate that an Arabidopsis mutant of a conserved ER stress sensor IRE1 exhibits defects in the auxin response and levels. These data not only support that the plant IRE1 is required for auxin homeostasis, they also reveal a species-specific feature of IRE1 in multicellular eukaryotes. Furthermore, by establishing that UPR activation is reduced in mutants of ER-localized auxin transporters, including PIN5, we define a long-neglected biological significance of ER-based auxin regulation. We further examine the functional relationship of IRE1 and PIN5 by showing that an ire1 pin5 triple mutant enhances defects of UPR activation and auxin homeostasis in ire1 or pin5. Our results imply that the plant UPR has evolved a hormone-dependent strategy for coordinating ER function with physiological processes.
authors.affiliation: Department of Energy Plant Research Laboratory, Department of Plant Biology, Michigan State University, East Lansing, MI, 48824, USA.
authors.forename: Yani
authors.initials: Y
authors.lastname: Chen
authors.forename: Kyaw
authors.initials: K
authors.lastname: Aung
authors.forename: Jakub
authors.initials: J
authors.lastname: Rolčík
authors.forename: Kathryn
authors.initials: K
authors.lastname: Walicki
authors.forename: Jiří
authors.initials: J
authors.lastname: Friml
authors.forename: Federica
authors.initials: F
authors.lastname: Brandizzi
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D015536:Down-Regulation; D004721:Endoplasmic Reticulum / Q000378:metabolism; D059865:Endoplasmic Reticulum Stress; D018506:Gene Expression Regulation, Plant; D006706:Homeostasis; D007210:Indoleacetic Acids / Q000032:analysis / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D008954:Models, Biological; D009154:Mutation; D010641:Phenotype; D010937:Plant Growth Regulators / Q000032:analysis / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000502:physiology; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D036226:Seedlings / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction; D013045:Species Specificity; D056811:Unfolded Protein Response
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins; C541719:PIN-FORMED 5 protein, Arabidopsis; D010937:Plant Growth Regulators; D010940:Plant Proteins; D011956:Receptors, Cell Surface; C046131:auxin receptor, plant; D011494:Protein Kinases; C446527:Ire1-1 protein, Arabidopsis; C446528:Ire1-2 protein, Arabidopsis
keywords: Arabidopsis thaliana; IRE1; PIN5; auxin response; endoplasmic reticulum stress; unfolded protein response