Barley coleoptile peroxidases. Purification, molecular cloning, and induction by pathogens

Area of Science:

• Plant biochemistry
• Molecular biology
• Plant pathology

Background:

• Peroxidases play crucial roles in plant defense mechanisms.
• Barley (Hordeum vulgare L.) produces antifungal compounds called hordatines.
• The specific role of Prx7 peroxidase in barley defense was previously unclear.

Purpose of the Study:

• To characterize the Prx7 peroxidase in barley.
• To investigate the expression and localization of Prx7 in response to powdery mildew infection.
• To determine if Prx7 is involved in hordatine biosynthesis.

Main Methods:

• cDNA cloning and protein prediction
• Immunoblotting and reverse-transcriptase polymerase chain reaction (RT-PCR)
• Enzyme purification and characterization (isoelectric focusing, mass spectrometry)
• Activity staining and subcellular localization studies

Main Results:

• Prx7 is a 341-amino acid protein with a predicted vacuolar localization.
• Prx7 protein and mRNA accumulate in barley coleoptiles and epidermis upon powdery mildew (Blumeria graminis) infection.
• Purified peroxidases P9.3 and P7.3 were identified as Prx7, with P9.3 being the pathogen-induced form.
• Prx7 accumulates in the vacuole of epidermal cells and appears to be the sole pathogen-induced vacuolar peroxidase.
• Prx7 is implicated in the biosynthesis of antifungal hordatines.

Conclusions:

• Prx7 is a key vacuolar peroxidase in barley's defense response.
• Prx7 expression is induced by powdery mildew and wounding.
• Prx7 likely contributes to antifungal defense through hordatine production.