Protective Role of Endogenous Nitric Oxide in the Response of Arabidopsis thaliana Against the UV-B Irradiation

AMENTA, M; LAMATTINA, L.; CASSIA, R.

Rosario, Argentina

Congreso; XXVII Reunión de la Sociedad Argentina de Fisiología Vegetal; 2008

Sociedad Argentina de Fisiología Vegetal

Nitric oxide (NO) is involved in plant responses to UV-B irradiation. To better understand the mechanisms underlying this response, we have used the transgenic NOD Arabidopsis plants, which express the Nitric Oxide Dioxygenase, a bacterial NO-degrading enzyme under the control of a dexamethasone (DEX) inducible promoter. For NO detection, Arabidopsis leaves  were loaded with the permeable fluorophore 4,5-diamino-fluorescein (DAF-FM-DA) a specific NO  probe. When NOD plants were treated with DEX (DEX+), they have shown a drop of 50% in the endogenous NO concentration respect to non-treated plants (DEX-) . DEX+ plants were more sensitive to UV-B than DEX-. Symptoms of chlorosis and high amounts of Reactive Oxygen Species (ROS) were observed when DEX+ were irradiated with UV-B during 60 min. Ion leakage, a measure of cell damage, augmented 100%, and chlorophyll decreased 40% in DEX+ respect to DEX- irradiated plants. The expression of genes related with flavonoids synthesis was analyzed by RT-PCR. Chalcone Synthase, Chalcone Isomerase and Dihydroflavonol Reductase increased in DEX- irradiated plants and this is coincident with the increased NO concentration registered in these plants. Altogether, our results support the idea that endogenous NO protects Arabidopsis plants against the UV-B irradiation. It is proposed that: (i) NO reduces oxidative damage acting as ROS scavenger, and (ii) NO induces the expression of genes involved in the flavonoids synthesis pathway. Flavonoids may, in turn, protect Arabidopsis from further UV-B irradiation. Financed by Conicet, ANPCyT and UNMDP.