Trichothecene NX-3 is required for Fusarium graminearum initial infection and disease spread

Authors: Hao, Guixia; Usgaard, Thomas; Tiley, Helene; McCormick, Susan; Vaughan, Martha; Ward, Todd

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/6/2021
Publication Date: 8/2/2021
Citation: Hao, G., Usgaard, T.R., Tiley, H.C., McCormick, S.P., Vaughan, M.M., Ward, T.J. 2021. Trichothecene NX-3 is required for Fusarium graminearum initial infection and disease spread [abstract].

Interpretive Summary:

Technical Abstract: The fungal pathogen Fusarium graminearum causes Fusarium head blight (FHB) on wheat, barley and other small grains. During infection, F. graminearum produces various mycotoxins that contaminate grains and result in unhealthy food and feed. In North America, three genetically distinct populations of F. graminearum have been identified and a different trichothecene chemotype predominates in each of these populations. 15-acetyldeoxynivalenol (15-ADON) predominates among NA1, 3-acetyldeoxynivalenol (3-ADON) predominates among NA2, and 3a-acetoxy, 7,15-dihydroxy-12,13-epoxytrichothec-9-ene (NX-2) is predominant among NA3. In planta both 3-ADON and 15-ADON are converted into DON, and NX-2 is converted into NX-3. Although it has been demonstrated that DON plays a critical role in the ability of F. graminearum to spread throughout the wheat head, it is unclear if NX-3 serves a similar function in FHB development. Therefore, we investigated the role of the trichothecene NX-3 during FHB development. Deletion mutants of Tri5, the first enzyme involved in trichothecene biosynthesis, were generated from representative strains of the three different North American populations (NA1 strain PH-1, NA2 strain 46422 and NA3 strain 44211). No trichothecene production was observed in any of the 'tri5 mutants. FHB symptoms were restricted to the inoculated wheat florets when point-inoculated with the 'tri5 mutants, confirming the necessity of DON and NX-3 for FHB spread. However, whole head dip inoculations which evaluate initial infection revealed a unique role of NX-3. Significant reductions in number of diseased florets and fungal biomass were observed in 44211'tri5 mutants compared to its parent strain 44211. Whereas no significant disease difference was observed between PH-1'tri5 and 46422'tri5 deletion mutants and their respective parent strains. Further experiments comparing barley infection by 44211'tri5 mutants and its parent are underway. Additionally, while 44211 displayed less FHB spread by point inoculation, it caused infection comparable to PH1 and 46422 when evaluated by whole head dip inoculation. Our results demonstrate that NX-3 is important for FHB development, and silencing the TRI5 gene in NA3 population may provide an effective tool to reduce FHB and mycotoxin contamination caused by this newly recognized population.