One of the most important functions of the plant hormone abscisic acid (ABA) is to induce stomatal closure by reducing the turgor of guard cells under water deficit. Under environmental stresses, hydrogen peroxide (H 2 O 2 ), an active oxygen species, is widely generated in many biological systems. Here, using an epidermal strip bioassay and laser-scanning confocal microscopy, we provide evidence that H 2 O 2 may function as an intermediate in ABA signaling in Vicia faba guard cells. H 2 O 2 inhibited induced closure of stomata, and this effect was reversed by ascorbic acid at concentrations lower than 10 Ϫ5 m. Further, ABA-induced stomatal closure also was abolished partly by addition of exogenous catalase (CAT) and diphenylene iodonium (DPI), which are an H 2 O 2 scavenger and an NADPH oxidase inhibitor, respectively. Time course experiments of single-cell assays based on the fluorescent probe dichlorofluorescein showed that the generation of H 2 O 2 was dependent on ABA concentration and an increase in the fluorescence intensity of the chloroplast occurred significantly earlier than within the other regions of guard cells. The ABA-induced change in fluorescence intensity in guard cells was abolished by the application of CAT and DPI. In addition, ABA microinjected into guard cells markedly induced H 2 O 2 production, which preceded stomatal closure. These effects were abolished by CAT or DPI micro-injection. Our results suggest that guard cells treated with ABA may close the stomata via a pathway with H 2 O 2 production involved, and H 2 O 2 may be an intermediate in ABA signaling.
The phytohormone abscisic acid (ABA) modulates the expression of many genes important to plant growth and development and to stress adaptation. In this study, we found that an APETALA2/EREBP-type transcription factor, AtERF7, plays an important role in ABA responses. AtERF7 interacts with the protein kinase PKS3, which has been shown to be a global regulator of ABA responses. AtERF7 binds to the GCC box and acts as a repressor of gene transcription. AtERF7 interacts with the Arabidopsis thaliana homolog of a human global corepressor of transcription, AtSin3, which in turn may interact with HDA19, a histone deacetylase. The transcriptional repression activity of AtERF7 is enhanced by HDA19 and AtSin3. Arabidopsis plants overexpressing AtERF7 show reduced sensitivity of guard cells to ABA and increased transpirational water loss. By contrast, AtERF7 and AtSin3 RNA interference lines show increased sensitivity to ABA during germination. Together, our results suggest that AtERF7 plays an important role in ABA responses and may be part of a transcriptional repressor complex and be regulated by PKS3.
We isolated two T-DNA insertion mutants of Arabidopsis thaliana GLUTATHIONE PEROXIDASE3 (ATGPX3) that exhibited a higher rate of water loss under drought stress, higher sensitivity to H 2 O 2 treatment during seed germination and seedling development, and enhanced production of H 2 O 2 in guard cells. By contrast, lines engineered to overexpress ATGPX3 were less sensitive to drought stress than the wild type and displayed less transpirational water loss, which resulted in higher leaf surface temperature. The atgpx3 mutation also disrupted abscisic acid (ABA) activation of calcium channels and the expression of ABA-and stress-responsive genes. ATGPX3 physically interacted with the 2C-type protein phosphatase ABA INSENSITIVE2 (ABI2) and, to a lesser extent, with ABI1. In addition, the redox states of both ATGPX3 and ABI2 were found to be regulated by H 2 O 2 . The phosphatase activity of ABI2, measured in vitro, was reduced approximately fivefold by the addition of oxidized ATGPX3. The reduced form of ABI2 was converted to the oxidized form by the addition of oxidized ATGPX3 in vitro, which might mediate ABA and oxidative signaling. These results suggest that ATGPX3 might play dual and distinctive roles in H 2 O 2 homeostasis, acting as a general scavenger and specifically relaying the H 2 O 2 signal as an oxidative signal transducer in ABA and drought stress signaling.
Contents Summary1I.1II.2III.4IV.5V.111212
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.