The Effect of Pseudomonas putida Colonization on Root Surface Peroxidase

Area of Science:

• Plant Pathology
• Microbial Ecology
• Biochemistry

Background:

• Root surfaces harbor microbial communities that can influence plant physiology.
• Plant enzymes like peroxidase and indole 3-acetic acid (IAA) oxidase play roles in growth and defense.
• Saprophytic bacteria can modulate plant enzyme activities, potentially affecting plant-pathogen interactions.

Purpose of the Study:

• To investigate the effects of Pseudomonas putida colonization on root surface enzyme activities in bean seedlings.
• To characterize the changes in peroxidase and IAA oxidase activities and identify specific enzyme isoforms.

Main Methods:

• Bean seedlings (Phaseolus vulgaris) were inoculated with Pseudomonas putida.
• Root surface washes were collected and analyzed for peroxidase and IAA oxidase activities.
• Native polyacrylamide gel electrophoresis and ion exchange/gel chromatography were used to separate and characterize enzyme fractions.

Main Results:

• A significant increase in root surface IAA oxidase (over 250-fold) and peroxidase (8-fold) activities was observed in P. putida-colonized seedlings.
• Enzyme activity enhancement was most pronounced in 6-day-old seedlings.
• Electrophoresis and chromatography revealed a specific, less anodic peroxidase fraction associated with P. putida inoculation, exhibiting a higher IAA oxidase to peroxidase ratio.

Conclusions:

• Colonization by the saprophytic bacterium Pseudomonas putida induces significant changes in root surface peroxidase and IAA oxidase activities in bean seedlings.
• A distinct peroxidase isoform appears to be upregulated upon bacterial colonization, potentially modulating auxin homeostasis.
• These findings contribute to understanding plant-microbe interactions and their implications for plant health and disease resistance.