The review examined the similarities and differences of the molecular mechanisms and environmental factors that regulate aflatoxin, fumonisin and trichothecene

Fumonisins are a group of mycotoxins that contaminate maize and cause leukoencephalomalacia in equine, pulmonary edema in swine, and promote cancer in mice. Fumonisin biosynthesis in Fusarium verticillioides is repressed by nitrogen and alkaline pH. We cloned a PACC-like gene (PAC1) from F. verticillioides. PACC genes encode the major transcriptional regulators of several pH-responsive pathways in other filamentous fungi. In Northern blot analyses, a PAC1 probe hybridized to a 2.2-kb transcript present in F. verticillioides grown at alkaline pH. A mutant of F. verticillioides with a disrupted PAC1 gene had severely impaired growth at alkaline pH. The mutant produced more fumonisin than the wild type when grown on maize kernels and in a synthetic medium buffered at an acidic pH, 4.5. The mutant, but not the wild type, also produced fumonisin B₁ when mycelia were resuspended in medium buffered at an alkaline pH, 8.4. Transcription of FUM1, a gene involved in fumonisin biosynthesis, was correlated with fumonisin production. We conclude that PAC1 is required for growth at alkaline pH and that Pac1 may have a role as a repressor of fumonisin biosynthesis under alkaline conditions.

Fusarium verticillioides, a fungal pathogen of maize, produces fumonisin mycotoxins that adversely affect human and animal health. Basic questions remain unanswered regarding the interactions between the host plant and the fungus that lead to the accumulation of fumonisins in maize kernels. In this study, we evaluated the role of kernel endosperm composition in regulating fumonisin B₁ (FB₁) biosynthesis. We found that kernels lacking starch due to physiological immaturity did not accumulate FB₁. Quantitative polymerase chain reaction analysis indicated that kernel development also affected the expression of fungal genes involved in FB₁ biosynthesis, starch metabolism, and nitrogen regulation. A mutant strain of F. verticillioides with a disrupted α-amylase gene was impaired in its ability to produce FB₁ on starchy kernels, and both the wild-type and mutant strains produced significantly less FB₁ on a high-amylose kernel mutant of maize. When grown on a defined medium with amylose as the sole carbon source, the wild-type strain produced only trace amounts of FB₁, but it produced large amounts of FB₁ when grown on amylopectin or dextrin, a product of amylopectin hydrolysis. We conclude that amylopectin induces FB₁ production in F. verticillioides. This study provides new insight regarding the interaction between the fungus and maize kernel during pathogenesis and highlights important areas that need further study.

The genus Fusarium comprises a diverse group of fungi including several species that produce mycotoxins in food commodities. In this study, a multiplex polymerase chain reaction (PCR) assay was dev...

Some species of Fusarium can produce mycotoxins during food processing procedures that facilitate fungal growth, such as the malting of barley. The objectives of this study were to develop a 5′ flu...