Hydrogen gas acts as a novel bioactive molecule in enhancing plant tolerance to paraquat-induced oxidative stress via the modulation of heme oxygenase-1 signalling system

Abstract

Hydrogen gas (H2) was recently proposed as a novel antioxidant and signalling molecule in animals. However, the physiological roles of H2 in plants are less clear. Here, we showed that exposure of alfalfa seedlings to paraquat stress increased endogenous H2 production. When supplied with exogenous H2 or the heme oxygenase-1 (HO-1)-inducer hemin, alfalfa plants displayed enhanced tolerance to oxidative stress induced by paraquat. This was evidenced by alleviation of the inhibition of root growth, reduced lipid peroxidation and the decreased hydrogen peroxide and superoxide anion radical levels. The activities and transcripts of representative antioxidant enzymes were induced after exposure to either H2 or hemin. Further results showed that H2 pre-treatment could dramatically increase levels of the MsHO-1 transcript, levels of the protein it encodes and HO-1 activity. The previously mentioned H2-mediated responses were specific for HO-1, given that the potent HO-1-inhibitor counteracted the effects of H2.The effects of H2 were reversed after the addition of an aqueous solution of 50% carbon monoxide (CO). We also discovered enhanced tolerance of multiple environmental stresses after plants were pre-treated with H2. Together, these results suggested that H2 might function as an important gaseous molecule that alleviates oxidative stress via HO-1 signalling.

Study details

Article type

Original Research

Disease / injury model

Paraquat-induced oxidative stress (herbicide-induced ROS stress)

Duration

24 hours

Dose comparison

Different concentrations of HRW (10%, 30%, 50%, 100%) were tested for their ability to alleviate paraquat-induced root growth inhibition, with 50% HRW showing the greatest effect.

Dose-dependent effect

Yes

Outcome

Positive

Findings

Exogenous hydrogen gas (H2) enhances alfalfa plant tolerance to paraquat-induced oxidative stress by alleviating root growth inhibition, reducing lipid peroxidation, and decreasing hydrogen peroxide and superoxide anion levels. H2 pretreatment increases antioxidant enzyme activities and gene expression, and these effects are mediated via the HO-1/CO signaling pathway. H2 also enhances tolerance to drought, salinity, and cold stress.