Nitric oxide enhances selenium concentration by promoting selenite uptake by rice roots

Nitric oxide (NO) plays a key role in regulating a wide range of physiological and biochemical processes. This study investigated possible effects of NO, which was supplied by sodium nitroprusside (SNP), NO donor, on selenium (Se) concentration, Se species within roots, activities and gene transcription of selenite uptake, and metabolism-related transporters or enzymes using ICP-MS, HPLC-ICP/MS, qRT-PCR, fluorescence imaging, and biochemical analysis in the roots of rice (Oryza sativa L.) seedling. A suitable SNP concentration (10 mu M) increased Se concentration in rice roots. NO enhanced the gene transcription of phosphate transporter OsPT2 and sulfate transporters OsSultr1;2 and OsSultr4;1 that contribute to selenite uptake. Furthermore, NO increased selenocysteine and methyl-selenocysteine concentrations in roots, stimulated glutathione biosynthesis by up-regulating the transcript levels of -glutamylcysteine synthetase (-ECS) and glutathione synthetase (GS), and increased cysteine synthase (CS) activity. In conclusion, our results indicate that NO promotes Se concentration of rice seedling roots by enhancing selenite uptake, up-regulating gene transcription of selenite uptake-related transporters, and increasing Se metabolism through regulating glutathione biosynthesis.