|Wipfler, Rebecca - Former ARS Employee|
|Alexander, Nancy - Retired ARS Employee|
Submitted to: Toxins
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/20/2019
Publication Date: 9/20/2019
Citation: Wipfler, R., McCormick, S.P., Proctor, R., Teresi, J., Hao, G., Ward, T., Alexander, N., Vaughan, M.M. 2019. Synergistic phytotoxic effects of culmorin and trichothecene mycotoxins. Toxins. 11(10):555. https://doi.org/10.3390/toxins11100555.
Interpretive Summary: Fusarium graminearum infects cereal crops and contaminates grain with the harmful toxin vomitoxin and other trichothecenes. The role of trichothecene toxins in plant disease development is well characterized, but less is known about other chemicals produced by F. graminearum and if they contribute to the toxicity or aid the fungus during plant infection This study tested the toxicity of culmorin, a chemical produced by F. graminearum, and culmorin-trichothecene mixtures on the model single cellular plant Chlamydomonas reinhardtii and on plant roots. By itself, culmorin did not affect plant cell growth. However, mixtures of culmorin with some trichothecenes resulted in a combined toxic effect that was greater than the additive effect of the individual compounds on roots of wheat, barley and corn. A study with 15 strains of F. graminearum found that the severity of Fusarium Head Blight disease was correlated with the sum of culmorin and vomitoxin produced by the isolates. Genomic analysis of Fusarium species found that genes for culmorin production and trichothecene production co-occur in other fungal species closely related to F. graminearum. These findings show that culmorin production provides an advantage to the pathogen by increasing toxicity and that reducing culmorin production could aid in the control of disease development and toxin contamination in grain.
Technical Abstract: Species of the fungus Fusarium cause Fusarium head blight (FHB) of cereal crops and contaminate grain with sesquiterpenoid mycotoxins including culmorin (CUL) and trichothecenes. While the phytotoxicity of trichothecenes, such as deoxynivalenol (DON), and their role in virulence are well characterized, less is known about the phytotoxicity of CUL and its role in development of FHB. Herein, we evaluated the phytotoxic effects of purified CUL and CUL-trichothecene mixtures using Chlamydomonas reinhardtii growth and plant root elongation assays. By itself, CUL did not affect growth in either system. However, mixtures of CUL with DON, 3-acetyldeoxynivalenol, 15-acetyldeoxynivalenol, or NX3, but not with nivalenol, inhibited growth in a synergistic manner. Synergistic phytotoxic effects of CUL and DON were also observed on multiple plant varieties and species. The severity of wheat FHB cause by 15 isolates of F. graminearum was negatively correlated with the CUL/DON ratio, but positively correlated with the sum of both CUL and DON. Additionally, during the first week of infection, CUL biosynthetic genes were more highly expressed than the TRI5 trichothecene biosynthetic gene. Furthermore, genomic analysis of Fusarium species revealed that CUL and trichothecene biosynthetic genes consistently co-occur among species closely related to F. graminearum.