Submitted to: PLoS One
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/18/2010
Publication Date: 3/24/2011
Citation: Ismail, Y., McCormick, S.P., Hijri, M. 2011. A fungal symbiont of plant-roots modulates mycotoxin gene expression in the pathogen Fusarium sambucinum. PLoS One. 6(3):1-7. Interpretive Summary: In this research, we determined that a mycorrhizal fungus, Glomus irregulare, can affect the genes that control the production of a trichothecene mycotoxin produced by Fusarium sambucinum-infected potato tubers. Mycorrhizal fungi form symbioses with plant roots that improve mineral uptake and protect the plants from soil-borne pathogens. F. sambucinum is the major cause worldwide of dry rot of potato tubers in the field and in storage. The present research found that G. irregulare both inhibited the growth of F. sambucinum and reduced the expression of some of the genes required to make trichothecene toxins. This research shows the potential of using mycorrhizal fungi to reduce mycotoxin contamination of potato crops.
Technical Abstract: Fusarium trichothecenes are fungal toxins that cause disease on infected plants and, more importantly, health problems for humans and animals that consume infected fruits or vegetables. Unfortunately, there are few methods for controlling the growth of mycotoxin production pathogens. In this study, we isolated and characterized sixteen Fusarium strains from naturally infected potato plants in the field. Pathogenicity tests were carried out in the green-house to evaluate the virulence of the trains on potato plants as well as their trichothecene production capacity and the most aggressive stain selected for further study. This strain, identified as F. sambucinum, was used to determine if trichothecene gene expression was affected by the symbiotic arbuscular mycorrhizal (AM) fungus Glomus irregulare. AM fungi form symbioses with plant roots, improving their mineral uptake and protecting plants against soil-borne pathogens. We find that G. irregulare significantly inhibits F. sambucinum growth. We also find, using RT-PCR assays to assess the relative expression of trichothecene genes, that in the presence of the AM fungus G. irregulare, F. sambucinum genes TRI5 and TRI6 were up-regulated, while TRI4, TRI13 and TRI101 were down regulated. We conclude that AM fungi can indeed modulate mycotoxin gene expression of a plant fungal pathogen. This previously undescribed effect may be a mechanism important for biological control and has fascinating implications for advancing our knowledge of plant-microbe interactions and controlling plant pathogens.