NX trichothecenes are required for Fusarium graminearum infection of wheat

Authors: Hao, Guixia; McCormick, Susan; TILEY, HELENE; GUTIERREZ, SANTIAGO - UNIVERSITY OF LEON; YULFO-SOTO, GABDIEL - OAK RIDGE INSTITUTE FOR SCIENCE AND EDUCATION (ORISE); Vaughan, Martha; Ward, Todd

Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/2023
Publication Date: 5/17/2023
Citation: Hao, G., McCormick, S., Tiley, H., Gutierrez, S., Yulfo-Soto, G., Vaughan, M.M., Ward, T.J. 2023. NX trichothecenes are required for Fusarium graminearum infection of wheat. Molecular Plant-Microbe Interactions. 36(5):294-304. https://doi.org/10.1094/MPMI-08-22-0164-R.
DOI: https://doi.org/10.1094/MPMI-08-22-0164-R

Interpretive Summary: Fusarium Head Blight (FHB) is a disease on wheat and other cereal crops that reduces yield and contaminates grain with deoxynivalenol (DON), a mycotoxin that can cause serious health problems in humans and animals. DON helps the fungus spread within the wheat plant. Control of FHB and mycotoxin contamination remains a challenge due to a lack of resistant plant varieties and emerging Fusarium strains. Recently, a new emerging Fusarium graminearum population was identified that produces a novel mycotoxin named NX. ARS researchers in Peoria, Illinois, investigated the role of NX toxin in Fusarium Head Blight. They deleted a gene that Fusarium needs to produce NX and performed multiple disease tests using the strains that cannot produce toxin. They found that NX toxin is critical for F. graminearum to infect the plant and spread disease. This research provides targets for biotechnology strategies such as RNA interference (RNAi) to reduce FHB and mycotoxin contamination simultaneously.

Technical Abstract: Fusarium graminearum causes Fusarium head blight (FHB) on wheat and barley and contaminates grains with various mycotoxins that are toxic to humans and animals. Deoxynivalenol (DON) is an essential virulence factor that is required for F. graminearum to spread within a wheat head. Recently, a novel type A trichothecene NX produced by F. graminearum has been characterized. NX shares a similar structure with DON but lacks a keto group at C8 position. To determine if the NX trichothecenes play a role similar to that of DON during F. graminearum infection, deletion mutants of TRI5, the first gene for trichothecene biosynthesis, were generated from strains (PH-1, NRRL 46422=46422, and NRRL 44211=44211) representing each of the major trichothecene chemotypes (15-ADON, 3-ADON, and NX). No trichothecene production was detected in any of the 'tri5 mutants in cultures or inoculated wheat heads. FHB symptoms were restricted to the inoculated wheat florets when point-inoculated with the 'tri5 mutants, confirming the necessity of NX and DON for FHB spread. Furthermore, whole head dip inoculations revealed significant reductions in disease and fungal biomass in wheat heads inoculated with 44211'tri5 compared to 44211. The function of 44211'tri5 did not complement by 44211 TRI5. Surprisingly, the function of 44211'tri5 was restored by introducing a TRI5 ortholog from Trichoderma arundinaceum. Our results demonstrate that NX type trichothecenes are critical for Fusarium graminearum initial infection and FHB spread and suggests TRI5 may serve as an ideal target to control plant infection, FHB spread and mycotoxin production simultaneously.