Perturbation of Indole-3-Butyric Acid Homeostasis by the UDP-GlucosyltransferaseUGT74E2ModulatesArabidopsisArchitecture and Water Stress Tolerance

Abstract

Reactive oxygen species and redox signaling undergo synergistic and antagonistic interactions with phytohormones to regulate protective responses of plants against biotic and abiotic stresses. However, molecular insight into the nature of this crosstalk remains scarce. We demonstrate that the hydrogen peroxide-responsive UDP-glucosyltransferase UGT74E2 of Arabidopsis thaliana is involved in the modulation of plant architecture and water stress response through its activity toward the auxin indole-3-butyric acid (IBA). Biochemical characterization of recombinant UGT74E2 demonstrated that it strongly favors IBA as a substrate. Assessment of indole-3-acetic acid (IAA), IBA, and their conjugates in transgenic plants ectopically expressing UGT74E2 indicated that the catalytic specificity was maintained in planta. In these transgenic plants, not only were IBA-Glc concentrations increased, but also free IBA levels were elevated and the conjugated IAA pattern was modified. This perturbed IBA and IAA homeostasis was associated with architectural changes, including increased shoot branching and altered rosette shape, and resulted in significantly improved survival during drought and salt stress treatments. Hence, our results reveal that IBA and IBA-Glc are important regulators of morphological and physiological stress adaptation mechanisms and provide molecular evidence for the interplay between hydrogen peroxide and auxin homeostasis through the action of an IBA UGT.

DEXH Box RNA Helicase–Mediated Mitochondrial Reactive Oxygen Species Production in Arabidopsis Mediates Crosstalk between Abscisic Acid and Auxin Signaling

“…Mutations in INDOLE-3-BUTYRIC ACID RE-SPONSE5 dual specificity phosphatase and RCN1 protein phosphatase 2A lead to auxin insensitivity but also to ABA insensitivity in germination and root growth. These studies highlight coenhancement between ABA and auxin signaling or auxin homeostasis during germination and seedling development (Liu et al, 2007;Belin et al, 2009;Tognetti et al, 2010). However, our results demonstrate that abo6 is sensitive to ABA mainly because of the reduced auxin levels caused by ROS overproduction.…”

Glycosyltransferases from Oat (Avena) Implicated in the Acylation of Avenacins

“…Other characterized UGT74 enzymes include an indole-3-acetic acid GT (ZmIAGT) from Z. mays (21), a crocetin GT (CsUGT2) from Crocus sativus (22), a gentisic acid xylosyltransferase from Solanum lycopersicum (SlGAGT) (23), a salicylic acid GT from Nicotiana tabacum (NtSAGTase) (24), a salicylic acid/anthranilic acid GT (UGT74F2), a thiohydroximate GT (AtUGT74B1) and a jasmonate GT (AtUGT74D1) from A. thaliana (25)(26)(27), and a triterpene GT from Saponaria vaccaria (synonym Vaccaria hispanica) (SvUGT74M1) that catalyzes the addition of glucose onto gypsogenic acid (28). A. thaliana UGT74E2 is thought to be an auxin indole-3-butyric acid glucosyltransferase (29) and UGT74C1 is implicated in aliphatic glucosinolate biosynthesis (30). Other predicted monocot UGT74 sequences from B. distachyon and O. sativa are also included in the tree shown in Fig.…”

Photorespiration Is Crucial for Dynamic Response of Photosynthetic Metabolism and Stomatal Movement to Altered CO 2 Availability

“…Its expression is H 2 O 2 inducible and leads to indole-3-butyric acid-dependent morphological changes in plants. An overexpression line for UGT74E2 produced leaves with reduced area and was more tolerant toward water stress (Tognetti et al, 2010). This compact rosette phenotype resembles the appearance of shm1 and glyk1 plants, 2 weeks after the shift from HC to LC conditions (Timm et al, 2012, Figure 6).…”