IIB   20738
INSTITUTO DE INVESTIGACIONES BIOLOGICAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Nitric Oxide, Abscisic Acid and Flavonoids: A Well-Equipped Team to Fight against UV-B Irradiation in Plants
Autor/es:
LAMATTINA, L.; TOSSI, V; AMENTA, M; CASSIA, R.
Lugar:
Santiago, Chile
Reunión:
Congreso; Free Radicals and Antioxidant in Chile; 2009
Institución organizadora:
SFREM South American Group
Resumen:
Nitric Oxide (NO) is a bioactive molecule that has mostly been studied in the plant kingdom during the last decade. It has been extensively demonstrated the role of NO as chemical cellular and inter-cellular messenger involved many signal transduction pathways operating during plant growth, developmental and stress physiology. However, one of the more important capabilities of NO is related to its chemical nature and ability in keeping redox and cellular homeostasis under stressing situations. Plants are sessile and photosynthetic organisms facing to many environmental stresses in the course of their life. Drought, UV-B, nutritional constraints are common factors affecting plant fitness and crop yield. All these adversities cause an over-production of reactive oxygen species (ROS) deriving in membrane and chloroplast damage, lower photosynthesis and a diminished plant efficiency to produce photo-assimilates. Results from our lab indicate that exogenous NO applications protect against high doses of UV-B in maize and potato plants. In maize leaves, UV-B induces NO production and this is dependent on a rapid and previous accumulation of the phytohormone Abscisic acid (ABA). Leaves of viviparous 14 (vp14), a maize mutant defective in ABA synthesis were more sensitive to UV-B than wild type (wt). Interestingly, vp14 mutant were unable to induce NO production upon UV-B irradiation. When vp14 were supplied with ABA or NO, plants recovered a full response to UV-B resulting in an increased protection against UV-B-derived damage. More recent pharmacological and genetic approaches showed a NO-dependent flavonoids biosynthesis as a key response in keeping low levels of cell damage in maize and Arabidopsis. To better understand the mechanisms underlying UV-B stimulus, we have used the transgenic NOD Arabidopsis plants expressing the Nitric Oxide Dioxygenase, a bacterial NO-degrading enzyme under the control of a dexamethasone (DEX) inducible promoter. DEX-treated NOD plants showed a drop of 50% in the endogenous NO content, and were extremely sensitive to UV-B measured as cell damage and high ROS concentration. The expression of genes associated to flavonoids biosynthesis was analyzed by qRT-PCR. Transcripts of Chalcone Synthase (CHS), Chalcone Isomerase (CHI) Dihydroflavonol Reductase (DFR) and Flavonol Synthase (FLS) increased in DEX(-)-irradiated NOD plants and this was coincident with the increase of NO concentration after UV-B irradiation. In contrast, DEX(+)-irradiated plants were unable to induce the expression of CHS, CHI and DFR. Thus, results indicate a strong correlation between NO levels, flavonoids concentration and increased tolerance to UV-B in plants. Altogether, our results support that ABA promotes a rapid NO production to: (i) reduce UV-B-derived oxidative damage and (ii) induce the expression of genes involved in the flavonoids synthesis to confer plants a sustained protection from further UV-B irradiation. Supported by UNMdP, CONICET and ANPCyT