Vacuolar transport of abscisic acid glucosyl ester is mediated by ATP-binding cassette and proton-antiport mechanisms in Arabidopsis

Plant Physiol. 2013 Nov;163(3):1446-58. doi: 10.1104/pp.113.222547. Epub 2013 Sep 12.

Abstract

Abscisic acid (ABA) is a key plant hormone involved in diverse physiological and developmental processes, including abiotic stress responses and the regulation of stomatal aperture and seed germination. Abscisic acid glucosyl ester (ABA-GE) is a hydrolyzable ABA conjugate that accumulates in the vacuole and presumably also in the endoplasmic reticulum. Deconjugation of ABA-GE by the endoplasmic reticulum and vacuolar β-glucosidases allows the rapid formation of free ABA in response to abiotic stress conditions such as dehydration and salt stress. ABA-GE further contributes to the maintenance of ABA homeostasis, as it is the major ABA catabolite exported from the cytosol. In this work, we identified that the import of ABA-GE into vacuoles isolated from Arabidopsis (Arabidopsis thaliana) mesophyll cells is mediated by two distinct membrane transport mechanisms: proton gradient-driven and ATP-binding cassette (ABC) transporters. Both systems have similar Km values of approximately 1 mm. According to our estimations, this low affinity appears nevertheless to be sufficient for the continuous vacuolar sequestration of ABA-GE produced in the cytosol. We further demonstrate that two tested multispecific vacuolar ABCC-type ABC transporters from Arabidopsis exhibit ABA-GE transport activity when expressed in yeast (Saccharomyces cerevisiae), which also supports the involvement of ABC transporters in ABA-GE uptake. Our findings suggest that the vacuolar ABA-GE uptake is not mediated by specific, but rather by several, possibly multispecific, transporters that are involved in the general vacuolar sequestration of conjugated metabolites.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP-Binding Cassette Transporters / genetics
  • ATP-Binding Cassette Transporters / metabolism*
  • Abscisic Acid / chemistry
  • Abscisic Acid / metabolism*
  • Abscisic Acid / pharmacology
  • Antiporters / metabolism*
  • Arabidopsis / genetics
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Biological Transport
  • Gene Expression Regulation, Plant / drug effects
  • Glucosides / chemistry
  • Glucosides / metabolism
  • Ion Transport
  • Mesophyll Cells / metabolism
  • Mutation
  • Plant Growth Regulators / chemistry
  • Plant Growth Regulators / metabolism
  • Plant Growth Regulators / pharmacology
  • Protons*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Vacuoles / metabolism*

Substances

  • ABCC1 protein, Arabidopsis
  • ABCC2 protein, Arabidopsis
  • ATP-Binding Cassette Transporters
  • Antiporters
  • Arabidopsis Proteins
  • Glucosides
  • Plant Growth Regulators
  • Protons
  • Abscisic Acid