|ZHANG, HUILI - Shenyang Agricultural University
|Chang, Perng Kuang
|MENG, XIANJUN - Shenyang Agricultural University
Submitted to: World Mycotoxin Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/19/2014
Publication Date: 2/2/2015
Citation: Zhang, H., Scharfenstein, L.L., Carter Wientjes, C.H., Chang, P., Zhang, D., Meng, X., Yu, J. 2015. Lack of aflatoxin production by Aspergillus flavus on a resistant peanut line is associated with delayed expression of aflatoxin genes. World Mycotoxin Journal. 8(3):335-340.
Interpretive Summary: Aflatoxins contaminate agricultural food commodities such as peanuts and corn. They are produced by two mold species called Aspergillus flavus and A. parasiticus. Aflatoxins are toxic to humans and animals, and also are capable of inducing liver cancer as evidenced in animal tests. Crop breeders are seeking host resistance to fungal infection as a key strategy to solve the problem of aflatoxin contamination on food and grains. In this study, we discovered that on a resistant peanut line infected with Aspergillus the fungus is unable to produce aflatoxins. Moreover, we showed that the block in aflatoxin production resulted from delayed expression of the key genes involved in biosynthesis of the toxic metabolites. This information will be helpful for peanut breeders to identify resistance genes and develop commercial peanut cultivars that are free of aflatoxin contamination.
Technical Abstract: Aflatoxins, produced by Aspergillus flavus and Aspergillus parasiticus, are the most toxic fungal secondary metabolites and the most potent carcinogens that contaminate agricultural commodities such as peanuts, cotton and corn. Understanding the underlying mechanisms of crop resistance to fungal infection is an important step for plant breeders to develop better and improved crop varieties for safe production of human food and animal feed. Infection studies have identified a resistant (R) peanut line, GT-C20, which is able to decrease aflatoxin contamination. The mycelial growth of A. flavus NRRL3357 on the R peanut line was much lower than that on the susceptible (S) peanut line, Tifrunner. Besides reducing fungal growth the R line compared to the S line inhibited aflatoxin production completely. Real-time RT-PCR assays of both the R and S lines infected by A. flavus showed that expression of five aflatoxin biosynthetic pathway genes, the aflR regulatory gene and the aflD, aflM, aflP and aflQ structural genes, was not reduced but was significantly delayed on the R line. The results suggested that resistance factors of the R line acted negatively on A. flavus growth and also altered fungal development. The dysfunction in development changed the timing and the pattern of aflatoxin gene expression, which in part rendered A. flavus unable to produce aflatoxins.