Cadmium affects peroxynitrite generation and tyrosine nitration in seedling roots of soybean (Glycine max L.)

The effect of short-term (48 h) moderate (85 mu M CdCl2) and high (174 mu M CdCl2) cadmium (Cd) stress on endogenous peroxynitrite (ONOO-) generation was investigated in the roots of 2-days old seedlings of soybean (Glycine max L). The control roots showed a relatively high level of ONOO-, whereas Cd-mediated ONOO- formation was detected only at high Cd stress. The Cd-induced ONOO- accumulation was accompanied by enhanced levels of both nitric oxide (NO) and superoxide (O-2(center dot-)). The contrasting response appeared during moderate stress which provoked a huge NADPH-oxidase dependent O-2(center dot-) accumulation with slightly elevated reactive nitrogen species formation. The nitroproteome analysis revealed a proteins pool undergoing tyrosine nitration that were down-regulated during both moderate and high Cd stress conditions. The most pronounced changes within the pool of 3-nitrotyrosine targets in soybean roots revealed proteins involved mainly in primary metabolism that are not implicated in plant defense strategy. Moreover, sequential treatment with ONOO- and Cd was tuned with diminished Cd toxicity and up-regulation of gene coding for peroxiredoxin (PrxII F). Taken together, soybean seedlings mainly exposed to moderate Cd stress, showed enhanced Pxr gene expression correlated with temperate ONOO- formation what finally affected post-translational protein modification via tyrosine nitration. (C) 2016 Elsevier B.V. All rights reserved.