Nitric oxide synthase-like dependent NO production enhances heme oxygenase up-regulation in

SANTA-CRUZ, DM; PACIENZA, N; POLIZIO, AH; BALESTRASSE, KB; TOMARO ML.; YANNARELLI, GG

PHYTOCHEMISTRY

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2010 vol. 71 p. 1700 - 1707

0031-9422

Heme oxygenase (HO) has antioxidant properties and is up-regulated by reactive oxygenspecies (ROS) in ultraviolet-B-irradiated soybean plants. This study shows that nitric oxide (NO) protects against oxidative damage and that nitric oxide synthase (NOS)-like activity is also required for HO-1 induction under UV-B radiation. Pre-treatments with sodium nitroprussiate (SNP), a NO-donor, prevented chlorophyll loss, H2O2 and O2.- accumulation, and ion leakage in UV-B-treated plants. HO activity was significantly enhanced by NO and showed a positive correlation with HO-1 transcript levels. In fact, HO-1 mRNA was increased 2.1-fold in 0.8 mM SNP-treated plants, whereas subsequent UV-B irradiation augmented this expression up to 3.5-fold with respect to controls. This response was not observed using ferrocyanide, a SNP inactive analog, and was effectively blocked by cPTIO, a specificNO scavenger. In addition, experiments carried out in the presence of L-NAME or tungsten, well-known inhibitors of NOS and nitrate reductase, showed that NOS is the endogenous source of NO that mediates HO-1 expression. In summary, we found that NO is involved in the signaling pathway leading to HO-1 up-regulation under UV-B, and that a balance between NO and ROS is important to trigger the antioxidant response against oxidative stress.