The wheat secreted root proteome: Implications for phosphorus mobilisation and biotic interactions

Area of Science:

• Plant Biology
• Molecular Biology
• Biochemistry

Background:

• Phosphorus (P) is crucial for plant growth but often limited in soils.
• Root exudates like acid phosphatases and organic anions are thought to mobilize P in the rhizosphere.
• Mechanisms of P mobilization in fine-rooted plants like wheat and the role of other root proteins are less understood.

Purpose of the Study:

• To characterize the extracellular proteome of wheat roots under P-limiting conditions.
• To investigate the role of root tip mucilage and secreted proteins in P mobilization.
• To identify proteins involved in plant adaptation to P deficiency.

Main Methods:

• Proteomic profiling of wheat root tip mucilage, soluble root exudates, and root tips.
• Targeted analysis of extracellular acid phosphatases and central carbon metabolism enzymes using selected reaction monitoring.
• Bioinformatic prediction of protein extracellular localization.

Main Results:

• Over 140 proteins with predicted extracellular localization were identified in root tip mucilage.
• P starvation induced apoplast-localized proteins involved in cell wall modification and defense.
• Extracellular acid phosphatases were not detected in extracellular samples; their role in P mobilization appears minor.
• Glycolytic enzymes, PEPC, and plastidial MDH increased in abundance in root tips under P limitation.

Conclusions:

• Wheat root tip mucilage proteins can actively modify the rhizosphere environment.
• Extracellular acid phosphatases play a limited role in P mobilization beyond the immediate root surface in wheat.
• Findings provide a resource for breeding P-efficient crops and understanding root-soil interactions.