Vacuolar Transport of Abscisic Acid Glucosyl Ester Is Mediated by ATP-Binding Cassette and Proton-Antiport Mechanisms in Arabidopsis

• Published in: Plant physiology (Bethesda) 2013-11, Vol.163 (3), p.1446-1458
• Main Authors: Burla, Bo, Pfrunder, Stefanie, Nagy, Réka, Francisco, Rita Maria, Lee, Youngsook, Martinoia, Enrico
• Format: Article
• Language: English
• Subjects: Abscisic Acid - chemistry; Abscisic Acid - metabolism; Abscisic Acid - pharmacology; Antiporters - metabolism; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; ATP binding cassette transporters; ATP-Binding Cassette Transporters - genetics; ATP-Binding Cassette Transporters - metabolism; Biological and medical sciences; Biological Transport; Drought; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Plant - drug effects; Glucosides - chemistry; Glucosides - metabolism; Ion Transport; MEMBRANES, TRANSPORT, AND BIOENERGETICS; Mesophyll; Mesophyll Cells - metabolism; Mutation; Plant cells; Plant Growth Regulators - chemistry; Plant Growth Regulators - metabolism; Plant Growth Regulators - pharmacology; Plant physiology and development; Plants; Protons; Radioactive decay; Reverse Transcriptase Polymerase Chain Reaction; Vacuoles; Vacuoles - metabolism; Vanadates; Yeasts
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.113.222547

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 K m values of approximately 1mM. 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.