Chitinase in bean leaves: induction by ethylene, purification, properties, and possible function

Area of Science:

• Plant biochemistry
• Molecular biology
• Plant pathology

Background:

• Ethylene is a plant hormone known to regulate various growth and stress responses.
• Chitinase enzymes play a role in plant defense mechanisms against pathogens.

Purpose of the Study:

• To investigate the induction of endochitinase by ethylene in Phaseolus vulgaris L.
• To characterize the properties and function of ethylene-induced chitinase.

Main Methods:

• Ethylene treatment of Phaseolus vulgaris L. primary leaves.
• Assay of chitinolytic activity using different chitin substrates.
• Enzyme purification via affinity chromatography.
• Molecular weight determination using SDS-PAGE and Sephadex G-75 filtration.
• Testing enzyme activity against fungal cell walls and bacteria.

Main Results:

• Ethylene significantly induced endochitinase activity in Phaseolus vulgaris L. leaves, with a 30-fold increase within 24 hours.
• The induced enzyme primarily exhibited endochitinase activity, with minimal exochitinase activity detected.
• Cycloheximide inhibited ethylene-induced chitinase activity, indicating de novo protein synthesis.
• Purified chitinase effectively degraded Fusarium solani cell walls and showed lysozyme activity against Micrococcus lysodeikticus.
• Ethylene-induced chitinase was also observed in various other plant species.

Conclusions:

• Ethylene-inducible endochitinase is a defense enzyme in plants, contributing to resistance against fungal and bacterial pathogens.
• The enzyme's ability to degrade chitin and its lysozyme-like activity highlight its role in plant immunity.