Molecular Hydrogen Is Involved in Phytohormone Signaling and Stress Responses in Plants

Abstract

Molecular hydrogen (H2) metabolism in bacteria and algae has been well studied from an industrial perspective because H2 is viewed as a potential future energy source. A number of clinical trials have recently reported that H2 is a therapeutic antioxidant and signaling molecule. Although H2 metabolism in higher plants was reported in some early studies, its biological effects remain unclear. In this report, the biological effects of H2 and its involvement in plant hormone signaling pathways and stress responses were determined. Antioxidant enzyme activity was found to be increased and the transcription of corresponding genes altered when the effects of H2 on the germination of mung bean seeds treated with phytohormones was investigated. In addition, upregulation of several phytohormone receptor genes and genes that encode a few key factors involved in plant signaling pathways was detected in rice seedlings treated with HW. The transcription of putative rice hydrogenase genes, hydrogenase activity, and endogenous H2 production were also determined. H2 production was found to be induced by abscisic acid, ethylene, and jasmonate acid, salt, and drought stress and was consistent with hydrogenase activity and the expression of putative hydrogenase genes in rice seedlings. Together, these results suggest that H2 may have an effect on rice stress tolerance by modulating the output of hormone signaling pathways.

Study details

Article type

Original Research

Disease / injury model

Abiotic stress (salt, drought) in plants

Duration

14 days

Dose comparison

The study compared low (100 mmol/L) and high (350 mmol/L) concentrations of hydrogen-rich water in rice seedlings (250 mmol for mung bean seedlings), finding that low concentrations accelerated plant growth while high concentrations suppressed it.

Dose-dependent effect

Yes

Outcome

Positive

Findings

Hydrogen-rich water (HW) modulates plant growth, enhances antioxidant enzyme activity, upregulates genes for phytohormone receptors and antioxidant enzymes, and increases endogenous hydrogen production in rice seedlings, especially under stress. H2 appears to act as both an antioxidant and a signaling molecule, improving plant stress tolerance by modulating hormone signaling pathways.