Repressor-AFLR interaction modulates aflatoxin biosynthesis in Aspergillus parasiticus.

Area of Science:

• Mycology
• Molecular Biology
• Biochemistry

Background:

• Aflatoxin (AF) biosynthesis is regulated by complex interactions of positive and negative factors.
• The AF pathway-specific regulatory gene, aflR, encodes the transcription factor AFLR, which controls AF gene expression.
• The role of the AFLR carboxyl region (AFLRC) in protein interactions and AF regulation is not fully understood.

Purpose of the Study:

• To investigate whether the AFLR carboxyl region interacts with proteins that positively or negatively regulate AF biosynthesis.
• To determine the effect of AFLRC expression on AF precursor production and sclerotial development.

Main Methods:

• The Aspergillus parasiticus aflR carboxyl coding region (aflRC) was fused to the promoter of the nitrite reductase gene (niiA(p)::aflRC).
• This construct was transformed into A. parasiticus SRRC 2043.
• The expression of niiA(p)::aflRC and its effect on AF precursor production and sclerotial development were analyzed in transformants with varying copy numbers of the integrated construct.

Main Results:

• Transformants with two copies of niiA(p)::aflRC overproduced AF precursors independently of the nitrogen source.
• Increased copy number of niiA(p)::aflRC correlated with higher AF precursor production and increased expression of both aflRC and native aflR.
• The expressed AFLRC, lacking a DNA-binding domain, likely titrates a repressor protein that interacts with AFLR.

Conclusions:

• The AFLR carboxyl region (AFLRC) appears to interact with a putative repressor, modulating AF biosynthesis.
• This interaction indirectly influences sclerotial development.
• The findings provide new insights into the complex regulatory mechanisms of aflatoxin production.