UV-B Induced Stomatal Closure in Arabidopsis is Regulated by the UVR8 Photoreceptor in an NO-Dependent Mechanism.

VANESA TOSSI ; LORENZO LAMATTINA; GARETH I. JENKINS; RAÚL CASSIA

PLANT PHYSIOLOGY.

AMER SOC PLANT BIOLOGISTS

Lugar: Rockville; Año: 2014 p. 2220 - 2230

0032-0889

Abstract Arabidopsis thaliana UV RESISTANCE LOCUS8 (UVR8) is a UV-B photoreceptor that mediates UV-B photomorphogenic responses. UVR8 signaling involves CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1), the ELONGATED HYPOCOTYL5 (HY5) transcription factor and the closely related HY5 HOMOLOG (HYH). 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. Stomata in abaxial epidermal strips of Arabidopsis Ler closed in response to increasing UV-B fluence rates, with maximal closure after 3 hours exposure to 5.46 μmol m-2 s-1 UV-B. Both H2O2 and NO increased in response to UV-B, and stomatal closure was maintained by NO up to 24 hours after the beginning of exposure.Stomata of plants expressing bacterial nitric oxide dioxygenase, which prevents NO accumulation, did not close in response to UVB, 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 GSNO induced closure of uvr8-1 stomata to the same extent as in wild-type. Experiments with mutants in UVR8 signaling components implicated COP1, HY5 and HYH 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.