Development and refinement of a high-efficiency gene-targeting system for Aspergillus flavus

Area of Science:

• Molecular Biology
• Mycology
• Genetics

Background:

• Aspergillus flavus is a significant fungal pathogen.
• Efficient gene-targeting systems are crucial for understanding fungal biology and developing control strategies.
• Existing methods for gene manipulation in A. flavus have limitations.

Purpose of the Study:

• To establish an efficient gene-targeting system in Aspergillus flavus.
• To utilize the nonhomologous end-joining pathway impairment and the pyrG gene for enhanced gene targeting.
• To demonstrate the system's utility in studying conidial pigment biosynthesis.

Main Methods:

• Impairment of the nonhomologous end-joining pathway by replacing the ku70 gene.
• Utilizing the Aspergillus oryzae pyrithiamine resistance (ptr) gene.
• Inserting the Aspergillus parasiticus cypA gene into the pyrG locus.
• Disruption of nine candidate genes involved in conidial pigment biosynthesis.

Main Results:

• Achieved high gene-targeting frequencies ranging from 80% to 100%.
• Confirmed the involvement of wA and olgA genes in pigment formation, leading to white and olive-green conidia.
• Refined the system with a reusable pyrG marker, restoring pyrithiamine sensitivity and uracil auxotrophy.
• Successfully restored laeA-mediated aflatoxin production in a laeA-deleted mutant.

Conclusions:

• The developed gene-targeting system is highly efficient for genetic manipulation in Aspergillus flavus.
• The system facilitates the study of fungal gene function, including pigment biosynthesis and aflatoxin production.
• The refined system with a reusable pyrG marker offers improved flexibility for future genetic studies.