Research articleHydrogen sulfide alleviates mercury toxicity by sequestering it in roots or regulating reactive oxygen species productions in rice seedlings

- Exogenous hydrogen sulfid (H2S) pretreatment promoted rice seedlings growth under Hg stress.
- H2S inhibited Hg transport from root to shoot.
- H2S increased bZIP60 and OsMT-1 expressions and NPT levels to sequester Hg in roots.
- H2S promoted seedlings growth even when the presences of Hg and SOD or CAT inhibitors.
- H2S attenuated Hg-induced oxidative damages in leaves by regulating O2·− and H2O2 productions.

Soil mercury (Hg) contamination is a major factor that affects agricultural yield and food security. Hydrogen sulfide (H2S) plays multifunctional roles in mediating a variety of responses to abiotic stresses. The effects of exogenous H2S on rice (Oryza sativa var 'Nipponbare') growth and metabolism under mercuric chloride (HgCl2) stress were investigated in this study. Either 100 or 200 μM sodium hydrosulfide (NaHS, a donor of H2S) pretreatment improved the transcription of bZIP60, a membrane-associated transcription factor, and then enhanced the expressions of non-protein thiols (NPT) and metallothioneins (OsMT-1) to sequester Hg in roots and thus inhibit Hg transport to shoots. Meanwhile, H2S promoted seedlings growth significantly even in the presences of Hg and superoxide dismutase (SOD, EC 1.15.1.1) or catalase (CAT, EC 1.11.1.6) inhibitors, diethyldithiocarbamate (DDC) or 3-amino-1,2,4-triazole (AT). H2S might act as an antioxidant to inhibit or scavenge reactive oxygen species (ROS) productions for maintaining the lower MDA and H2O2 levels, and thereby preventing oxidative damages. All these results indicated H2S effectively alleviated Hg toxicity by sequestering it in roots or by regulating ROS in seedlings and then thus significantly promoted rice growth.