Abscisic Acid Uridine Diphosphate Glucosyltransferases Play a Crucial Role in Abscisic Acid Homeostasis in Arabidopsis

• Published in: Plant physiology (Bethesda) 2014-05, Vol.165 (1), p.277-289
• Main Authors: Dong, Ting, Xu, Zheng-Yi, Park, Youngmin, Kim, Dae Heon, Lee, Yongjik, Hwang, Inhwan
• Format: Article
• Language: English
• Subjects: Abscisic Acid - metabolism; Abscisic Acid - pharmacology; Arabidopsis - drug effects; Arabidopsis - enzymology; Arabidopsis - genetics; Arabidopsis - physiology; Arabidopsis Proteins - metabolism; Biosynthesis; Cytosol - drug effects; Cytosol - enzymology; Dehydration; Gene Expression Regulation, Plant - drug effects; Germination; Germination - drug effects; Glucosyltransferases - metabolism; Glycosyltransferases - metabolism; Green Fluorescent Proteins - metabolism; Homeostasis; Homeostasis - drug effects; Hydroxylation - drug effects; Mutation - genetics; Osmosis - drug effects; Phenotype; Phenotypes; Plant cells; Plants; Protein Transport - drug effects; Protoplasts; Recombinant Fusion Proteins - metabolism; RNA; RNA Interference; Sequence Homology, Amino Acid; SIGNALING AND RESPONSE; Sodium Chloride - pharmacology; Solubility; Stress, Physiological - drug effects; Transgenic plants; Uridine Diphosphate - metabolism
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.114.239210

The phytohormone abscisic acid (ABA) is crucial for plant growth and adaptive responses to various stress conditions. Plants continuously adjust the ABA level to meet physiological needs, but how ABA homeostasis occurs is not fully understood. This study provides evidence that UGT71B6, an ABA uridine diphosphate glucosyltransferase (UGT), and its two closely related homologs, UGT71B7 and UGT71B8, play crucial roles in ABA homeostasis and in adaptation to dehydration, osmotic stress, and high-salinity stresses in Arabidopsis (Arabidopsis thaliana). UGT RNA interference plants that had low levels of these three UGT transcripts displayed hypersensitivity to exogenous ABA and high-salt conditions during germination and exhibited a defect in plant growth. However, the ectopie expression of UGT71B6 in the atbgl (for β-glucosidase) mutant background aggravated the ABA-defìcient phenotype of atbgl mutant plants. In addition, modulation of the expression of the three UGTs affects the expression of CYP707A1 to CYP707A4, which encode ABA 8'-hydroxylases; four CYP707As were expressed at higher levels in the UGT RNA interference plants but at lower levels in the UGT71B6:GFP-overexpressing plants. Based on these data, this study proposes that UGT71B6 and its two homologs play a critical role in ABA homeostasis by converting active ABA to an inactive form (abscisic acid-glucose ester) depending on intrinsic cellular and environmental conditions in plants.