Processing and release of the maize phytocytokine Zip1

Area of Science:

• Plant Molecular Biology
• Plant Immunity
• Biochemistry

Background:

• Phytocytokines are key regulators of plant immune responses.
• Mechanisms controlling phytocytokine maturation and spatial deployment are largely unknown.

Purpose of the Study:

• To elucidate the proteolytic processing and secretion pathway of the maize phytocytokine precursor PROZIP1.
• To understand how this pathway contributes to spatial and temporal control of plant immunity.

Main Methods:

• Proteomic mapping and mutational analyses of PROZIP1.
• Investigating the role of metacaspases and cysteine proteases in PROZIP1 processing.
• Tracking PROZIP1 localization and processing in maize.

Main Results:

• PROZIP1 undergoes intracellular, arginine-dependent processing by metacaspases (ZmMC9) to generate Ct-PROZIP1.
• Ct-PROZIP1 is secreted via an ER-Golgi-independent route.
• Extracellular proteases further process Ct-PROZIP1, regulating signal clearance and turnover.
• Ct-PROZIP1 is identified as the primary signaling molecule modulating immunity.

Conclusions:

• A novel, spatially separated, two-stage proteolytic pathway controls maize phytocytokine activity.
• This pathway uncouples signal activation from extracellular attenuation, providing precise temporal and spatial control.
• Findings reveal complexity in peptide signaling, offering insights into plant disease modulation.