title: Environmental Nitrate Stimulates Abscisic Acid Accumulation in Arabidopsis Root Tips by Releasing It from Inactive Stores.
abstract: Abscisic acid (ABA) signaling plays a major role in root system development, regulating growth and root architecture. However, the precise localization of ABA remains undetermined. Here, we present a mechanism in which nitrate signaling stimulates the release of bioactive ABA from the inactive storage form, ABA-glucose ester (ABA-GE). We found that ABA accumulated in the endodermis and quiescent center of Arabidopsis thaliana root tips, mimicking the pattern of SCARECROW expression, and (to lower levels) in the vascular cylinder. Nitrate treatment increased ABA levels in root tips; this stimulation requires the activity of the endoplasmic reticulum-localized, ABA-GE-deconjugating enzyme b-GLUCOSIDASE1, but not de novo ABA biosynthesis. Immunogold labeling demonstrated that ABA is associated with cytoplasmic structures near, but not within, the endoplasmic reticulum. These findings demonstrate a mechanism for nitrate-regulated root growth via regulation of ABA accumulation in the root tip, providing insight into the environmental regulation of root growth.
authors.affiliation: Department of Plant Biology, University of Vermont, Burlington, Vermont 05405 Department of Plant Sciences, The University of Tennessee, Knoxville, Tennessee 37996.
authors.forename: Christine A
authors.identifier: http://orcid.org/0000-0001-9184-9525
authors.initials: CA
authors.lastname: Ondzighi-Assoume
authors.affiliation: Department of Plant Biology, University of Vermont, Burlington, Vermont 05405.
authors.forename: Sanhita
authors.identifier: http://orcid.org/0000-0001-7991-3977
authors.initials: S
authors.lastname: Chakraborty
authors.affiliation: Department of Plant Biology, University of Vermont, Burlington, Vermont 05405 jmharris@uvm.edu.
authors.forename: Jeanne M
authors.identifier: http://orcid.org/0000-0003-1971-484X
authors.initials: JM
authors.lastname: Harris
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D017360:Arabidopsis / Q000166:cytology / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D018519:Meristem / Q000166:cytology / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D009566:Nitrates / Q000494:pharmacology*; D009928:Organ Specificity; D010937:Plant Growth Regulators / Q000378:metabolism*; D018517:Plant Roots / Q000166:cytology / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D030821:Plants, Genetically Modified; D012639:Seeds / Q000166:cytology / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D009566:Nitrates; D010937:Plant Growth Regulators; D000040:Abscisic Acid