Gene expression profile and response to maize kernels by Aspergillus flavus

Area of Science:

• Plant Pathology
• Mycology
• Agricultural Science

Background:

• Aspergillus flavus causes maize ear rot and produces aflatoxins, posing risks to human and animal health.
• The impact of the maize kernel environment on A. flavus colonization and aflatoxin biosynthesis remains incompletely understood.

Purpose of the Study:

• To investigate the genome-wide transcriptional response of A. flavus to different developmental stages of the maize kernel.
• To elucidate the role of specific genes, such as phytase, in A. flavus pathogenesis within the maize kernel environment.

Main Methods:

• Gene expression analysis using microarrays on A. flavus grown on maize kernels at four developmental stages (R2-R5).
• Isolation and characterization of total RNA for hybridization to Affymetrix Gene Chip arrays.
• Genetic manipulation of the phytase gene (phy1) to assess its role in fungal growth and pathogenesis.

Main Results:

• Significant differences in A. flavus gene expression were observed across kernel developmental stages, with unique gene sets upregulated at each stage.
• A phytase gene (phy1) and zinc acquisition genes were upregulated in colonized dent kernels.
• Disruption of phy1 led to reduced fungal growth on phytate-containing media and impaired virulence in maize ears, without affecting aflatoxin production.

Conclusions:

• Immature maize kernels significantly influence A. flavus gene expression.
• Phytase plays a role in A. flavus pathogenesis on maize, likely by facilitating nutrient acquisition.
• The phy1 gene is not essential for aflatoxin biosynthesis in this maize ear rot model.