Rice transcription factor bHLH25 confers resistance to multiple diseases by sensing H₂O₂

Area of Science:

• Plant Biology
• Molecular Biology
• Biochemistry

Background:

• Hydrogen peroxide (H2O2) is a key signaling molecule in eukaryotic innate immunity.
• The precise mechanisms by which transcription factors directly sense H2O2 remain largely unelucidated.

Purpose of the Study:

• To identify and characterize transcription factors that directly sense H2O2 in plants.
• To elucidate the molecular mechanism of H2O2 sensing by transcription factors in plant defense.

Main Methods:

• Investigated the role of rice bHLH25 in plant defense responses.
• Utilized molecular biology techniques to analyze H2O2-mediated oxidation of bHLH25.
• Examined the regulation of downstream genes including miR397b, lignin biosynthesis, and Copalyl Diphosphate Synthase 2 (CPS2).

Main Results:

• Rice bHLH25 directly senses H2O2 through oxidation at methionine 256.
• Oxidized bHLH25 represses miR397b, promoting lignin biosynthesis for cell wall reinforcement.
• Non-oxidized bHLH25 activates CPS2, leading to phytoalexin biosynthesis.
• This dual-action mechanism optimizes H2O2, lignin, and phytoalexin levels for effective pathogen resistance.

Conclusions:

• A novel H2O2 sensing mechanism by bHLH25 regulates distinct plant defense pathways.
• The conserved methionine oxidation site suggests this mechanism is widespread in plants.
• This Met-oxidation mechanism may be applicable to other eukaryotic transcription factors sensing H2O2.