Pyrrocidine, a molecular off switch for fumonisin biosynthesis

Area of Science:

• Agricultural Science
• Mycology
• Plant Pathology

Background:

• Sarocladium zeae and Fusarium verticillioides are fungal endophytes co-inhabiting maize seeds.
• F. verticillioides is a significant mycotoxigenic threat, producing fumonisins.
• S. zeae produces pyrrocidines A and B, which inhibit F. verticillioides growth.

Purpose of the Study:

• To investigate the physiological response of F. verticillioides to pyrrocidines.
• To identify genes in F. verticillioides involved in pyrrocidine resistance and fumonisin regulation.
• To understand how S. zeae influences mycotoxin production in F. verticillioides.

Main Methods:

• Transcriptome sequencing of F. verticillioides exposed to pyrrocidines A and B.
• Identification and characterization of F. verticillioides genes FvABC3 and FvZBD1.
• Gene deletion experiments to assess the role of FvZBD1 in fumonisin production.

Main Results:

• FvABC3 transporter identified as critical for pyrrocidine resistance in F. verticillioides.
• FvZBD1 gene, adjacent to the fumonisin cluster, significantly induced by pyrrocidines.
• Deletion of FvZBD1 led to a massive increase in fumonisin production, indicating its role as a repressor.
• Pyrrocidine exposure, likely via FvZBD1, suppresses fumonisin biosynthesis.

Conclusions:

• S. zeae's pyrrocidines actively manipulate F. verticillioides' secondary metabolism.
• This interaction represses fumonisin production, a key mycotoxin.
• S. zeae may use this mechanism for competitive advantage and self-protection.
• The findings have implications for maize food safety and understanding fungal interactions.