Biosynthesis of wound ethylene

Area of Science:

• Plant Physiology
• Biochemistry
• Molecular Biology

Background:

• Ethylene (C2H4) is a crucial plant hormone regulating various growth and developmental processes.
• Wounding and certain metal ions can trigger ethylene production, but the underlying molecular mechanisms are not fully elucidated.

Purpose of the Study:

• To investigate the role of 1-aminocyclopropane-1-carboxylic acid (ACC) and ACC synthase in wound-induced ethylene production.
• To determine the effect of copper (Cu2+) and calcium (Ca2+) ions on ethylene biosynthesis in mung bean hypocotyls.

Main Methods:

• Treatment of mung bean hypocotyls with Cu2+ and Ca2+ ions.
• Measurement of ethylene production, ACC content, and S-adenosylmethionine (SAM) levels.
• Application of aminoethoxyvinylglycine (AVG), an ACC synthase inhibitor.
• Excision of orange albedo and green tomato fruit tissues.
• Infiltration with cycloheximide, a protein synthesis inhibitor.

Main Results:

• Cu2+ and Cu2+ + Ca2+ treatments increased ethylene production 20- and 40-fold in mung beans, respectively.
• Increased ACC content paralleled ethylene production, while SAM levels remained unchanged.
• AVG treatment inhibited wound-induced ACC and ethylene production.
• Excision of plant tissues led to increased ACC content and ethylene production.
• Cycloheximide blocked wound-induced ethylene production, ACC formation, and ACC synthase activity.

Conclusions:

• The conversion of SAM to ACC is a rate-limiting step in wound-induced ethylene biosynthesis.
• Wounding induces the synthesis of ACC synthase, which is the key enzyme controlling ethylene production.
• Copper ions can significantly stimulate ethylene biosynthesis in plants.