Rethinking polyphenol oxidases in wheat: beyond the "low-PPO is always better" paradigm

Area of Science:

• Plant biochemistry
• Wheat genetics
• Enzyme function

Background:

• Polyphenol oxidase (PPO) activity is crucial for wheat quality and defense against stresses.
• Understanding PPO allelic diversity is vital for wheat breeding and crop improvement.

Purpose of the Study:

• To comprehensively characterize PPO alleles in bread and durum wheat.
• To explore the structural and functional diversity of Ppo genes across wheat genomes.
• To challenge the notion that low PPO activity is always optimal.

Main Methods:

• Structural characterization of over 25 Ppo alleles from Ppo-1 and Ppo-2 gene families.
• Comparative analysis of Ppo gene alleles across the A, B, and D genomes of wheat.
• Synthesis of existing evidence on PPO activity, plant defense, and end-product quality.

Main Results:

• Extensive allelic diversity in Ppo-1 and Ppo-2 gene families identified between bread and durum wheat.
• Significant structural polymorphisms in Ppo genes contribute to functional diversification.
• Higher PPO activity correlates with enhanced plant defense, challenging the 'low-PPO is better' assumption.

Conclusions:

• A broad repertoire of PPO alleles provides a toolkit for fine-tuning enzyme activity for adaptation and quality.
• Excessive PPO suppression may compromise plant resilience.
• A paradigm shift towards strategic PPO modulation is needed to balance defense and quality.