|LOHMAR, JESSICA - Northern Illinois University|
|Harris Coward, Pamela|
|DHINGRA, SOURABH - Northern Illinois University|
|CALVO, ANA - Northern Illinois University|
Submitted to: Applied Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2016
Publication Date: 3/28/2016
Citation: Lohmar, J.M., Harris-Coward, P.Y., Cary, J.W., Dhingra, S., Calvo, A.M. 2016. rtfA, a putative RNA-Pol II transcription elongation factor gene, is necessary for normal morphological and chemical development in Aspergillus flavus. Applied Microbiology and Biotechnology. 100(11):5029-5041. doi:10.1007/s00253-016-7418-7.
Interpretive Summary: This work describes experiments that have been conducted in an effort to better understand the genetic mechanisms that control aflatoxin production and growth and development in Aspergillus flavus. Aflatoxins are toxic and carcinogenic compounds often produced by the fungi, Aspergillus flavus during growth on crops such as corn, peanuts, cottonseed, and treenuts. Because of the potential health risks, aflatoxin contamination of food and feed crops is also of great economic importance to farmers who cannot sell their crops due to strict domestic and international regulatory guidelines with regards to aflatoxin contamination. We have succeeded identifying a gene, designated rtfA, from A. flavus that when inactivated significantly reduces the ability of the fungus to produce aflatoxin and also reduces the numbers of structures known as conidia and sclerotia that help the fungus to spread and survive in the field under adverse conditions. In addition, this study showed that rtfA controls the production of other secondary metabolites produced by A. flavus. Identification of rtfA will add to our knowledge of regulation of growth and toxin production in A. flavus and this in turn will help in devising strategies for eliminating fungal toxin contamination of food and feed crops.
Technical Abstract: The filamentous fungus Aspergillus flavus is an agriculturally important opportunistic plant pathogen that produces potent carcinogenic compounds called aflatoxins. We identified the A. flavus rtfA gene, the ortholog of rtf1 in S. cerevisiae and rtfA in A. nidulans. Interestingly, rtfA has multiple cellular roles in this mycotoxin-producing fungus. In this study, we show that rtfA regulates conidiation. The rtfA deletion mutant presented smaller conidiophores with significantly reduced conidial production compared to the wild-type strain. The absence of rtfA also resulted in a significant decrease or lack of sclerotial production under conditions that allowed abundant production of these resistance structures in the wild type. Importantly, the deletion of rtfA notably reduced the production of aflatoxin B1, indicating that rtfA is a regulator of mycotoxin biosynthesis in A. flavus. In addition, the deletion rtfA also altered the production of several unknown secondary metabolites indicating a broader regulatory scope. Furthermore, our study revealed that rtfA controls the expression of the global regulators veA and laeA, which further influence morphogenesis and secondary metabolism in A. flavus.