Cleavage of PrePL by Lon promotes growth and pathogenesis in Magnaporthe oryzae

Area of Science:

• Mycology
• Plant Pathology
• Molecular Biology

Background:

• ATP-dependent Lon proteases regulate bacterial virulence by controlling Type III secretion systems.
• The role of Lon proteases in fungal pathogenesis remains largely unexplored.
• PrePL is a Magnaporthe oryzae Lon-binding protein previously identified in our lab.

Purpose of the Study:

• To investigate the role of Magnaporthe oryzae Lon protease in fungal pathogenesis.
• To identify and characterize the function of PrePL and its cleaved products.
• To determine if PrePL or its isoforms act as avirulence factors.

Main Methods:

• Generating a ΔPrePL loss-of-function strain.
• Analyzing the cleavage of PrePL by Lon protease.
• Characterizing the enzymatic activity of the cleaved product (Pc).
• Assessing the impact of PrePL and Pc on fungal development and plant disease progression.
• Infiltrating recombinant Pc into plant leaves to observe plant defense responses.

Main Results:

• Lon protease cleaves full-length PrePL into an 11-kDa extracellular isoform, Pc, with catalase and peroxidase activity.
• Loss of PrePL (ΔPrePL) resulted in enhanced sporulation and accelerated disease development.
• Both full-length PrePL and Pc are crucial for fungal development, as neither could fully complement the ΔPrePL phenotype.
• Pc accumulates in the fungal apoplast and functions as an avirulence factor, inducing plant defense responses and cell death.

Conclusions:

• This study reveals a novel pathogenic factor, Pc, within the fungal Lon-mediated pathway.
• PrePL acts as a negative regulator of fungal disease progression.
• The cleaved isoform Pc functions as an avirulence factor, highlighting a new mechanism in fungal pathogenesis.
• This work provides insights into the dual roles of a full-length protein and its cleaved isoform in fungal development and virulence.