Differential peroxidase activities in three different crops upon insect feeding

Area of Science:

• Plant Science
• Biochemistry
• Enzymology

Background:

• Peroxidases are vital enzymes found across all living organisms.
• They catalyze peroxide reduction, generating reactive oxygen species.
• Plant peroxidases play crucial roles in defense mechanisms.

Purpose of the Study:

• To investigate the effect of insect infestation on peroxidase activity in crop plants.
• To quantify changes in peroxidase levels in response to different insect feeding types.
• To analyze the kinetic properties and identify peroxidases in affected plants.

Main Methods:

• Insect infestation of tomato, cowpea, and cotton plants.
• Measurement of peroxidase activity in plant sap and total soluble protein (TSP).
• In-gel peroxidase assay, enzyme kinetics, and MS/MS analysis for enzyme identification.

Main Results:

• Insect infestation, both chewing and sap-sucking, significantly enhanced peroxidase activity (1.6-3.14 fold and 1.8-2.53 fold, respectively).
• In-gel assays confirmed elevated peroxidase activity.
• Enzyme kinetic studies revealed high turnover efficiencies, with cotton and tomato peroxidases showing similar rates (~100 min⁻¹).
• MS/MS analysis identified known peroxidases in the analyzed bands.

Conclusions:

• Insect infestation is a potent inducer of peroxidase activity in crop plants.
• Elevated peroxidase levels suggest a role in plant defense against insect herbivory.
• The identified peroxidases exhibit efficient catalytic activity, contributing to plant stress response.