Ethylene insensitivity modulates ozone-induced cell death in birch

Area of Science:

• Plant Physiology
• Environmental Stress Response
• Biochemistry

Background:

• Ozone (O3) is a major air pollutant causing significant damage to plants.
• Hormonal signaling pathways, including ethylene (ET), jasmonic acid, and salicylic acid, are implicated in plant responses to O3 stress.
• Understanding the specific roles of these hormones is crucial for predicting and mitigating O3-induced plant injury.

Purpose of the Study:

• To investigate the roles of ethylene, jasmonic acid, and salicylic acid in regulating birch (Betula pendula Roth) tissue tolerance to O3.
• To elucidate the specific mechanisms by which ethylene influences O3-induced cell death and detoxification pathways.

Main Methods:

• Utilized genotypic variation in birch to study O3 responses.
• Manipulated ethylene perception using the dominant-negative etr1-1 mutant and 1-methylcyclopropene.
• Inhibited ethylene biosynthesis using aminooxyacetic acid.
• Assessed O3-induced cell death and gene expression, specifically for beta-cyanoalanine synthase.

Main Results:

• Ethylene evolution showed the strongest correlation with O3-induced cell death.
• Disrupting ethylene perception reduced but did not eliminate O3-induced cell death.
• Inhibiting ethylene biosynthesis completely prevented O3 lesion formation.
• Functional ethylene signaling was necessary for O3 induction of beta-cyanoalanine synthase, an enzyme involved in cyanide detoxification.

Conclusions:

• Ethylene signaling is essential for protecting birch from O3-induced cell death.
• A component of ethylene-mediated cell death stimulation is independent of ethylene signaling but dependent on ethylene biosynthesis.
• Reduced ethylene sensitivity combined with high ethylene biosynthesis may cause cell death due to impaired cyanide detoxification.