title: Ultraviolet-B-induced stomatal closure in Arabidopsis is regulated by the UV RESISTANCE LOCUS8 photoreceptor in a nitric oxide-dependent mechanism.
abstract: UV RESISTANCE LOCUS8 (UVR8) signaling involves CONSTITUTIVELY PHOTOMORPHOGENIC1, the ELONGATED HYPOCOTYL5 (HY5) transcription factor, and the closely related HY5 HOMOLOG. Some UV-B responses mediated by UVR8 are also regulated by nitric oxide (NO), a bioactive molecule that orchestrates a wide range of processes in plants. In this study, we investigated the participation of the UVR8 pathway and its interaction with NO in UV-B-induced stomatal movements in Arabidopsis (Arabidopsis thaliana). Stomata in abaxial epidermal strips of Arabidopsis ecotype Landsberg erecta closed in response to increasing UV-B fluence rates, with maximal closure after 3-h exposure to 5.46 μmol m⁻² s⁻¹ UV-B. Both hydrogen peroxide (H₂O₂) and NO increased in response to UV-B, and stomatal closure was maintained by NO up to 24 h after the beginning of exposure. Stomata of plants expressing bacterial NO dioxygenase, which prevents NO accumulation, did not close in response to UV-B, although H₂O₂ still increased. When the uvr8-1 null mutant was exposed to UV-B, stomata remained open, irrespective of the fluence rate. Neither NO nor H₂O₂ increased in stomata of the uvr8-1 mutant. However, the NO donor S-nitrosoglutathione induced closure of uvr8-1 stomata to the same extent as in the wild type. Experiments with mutants in UVR8 signaling components implicated CONSTITUTIVELY PHOTOMORPHOGENIC1, HY5, and HY5 HOMOLOG in UV-B-induced stomatal closure. This research provides evidence that the UVR8 pathway regulates stomatal closure by a mechanism involving both H₂O₂ and NO generation in response to UV-B exposure.
authors.affiliation: Instituto de Investigaciones Biológicas, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata-Consejo Nacional de Investigaciones Científicas y Técnicas, CC1245 (7600) Mar del Plata, Argentina.
authors.forename: Vanesa
authors.initials: V
authors.lastname: Tossi
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Lamattina
authors.forename: Gareth I
authors.initials: GI
authors.lastname: Jenkins
authors.forename: Raúl O
authors.initials: RO
authors.lastname: Cassia
mesh_terms: D017360:Arabidopsis / Q000502:physiology* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002470:Cell Survival / Q000528:radiation effects; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism; D008954:Models, Biological; D009569:Nitric Oxide / Q000378:metabolism*; D055519:Photoreceptors, Plant / Q000378:metabolism*; D054046:Plant Stomata / Q000502:physiology* / Q000528:radiation effects*; D015398:Signal Transduction / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D029681:Arabidopsis Proteins; D002868:Chromosomal Proteins, Non-Histone; D055519:Photoreceptors, Plant; C525052:Uvr8 protein, Arabidopsis; D009569:Nitric Oxide; D006861:Hydrogen Peroxide