Abstract
Fusarium mycotoxins, deoxynivalenol (DON) and nivalenol (NIV) act as virulence factors and are essential for symptom development after initial infection in wheat. To date, 16 genes have been identified in the DON biosynthesis pathway. However, a comparative gene expression analysis in different chemotypes of Fusarium graminearum in response to Fusarium head blight infection remains to be explored. Therefore, in this study, nine genes that involved in trichothecene biosynthesis were analyzed among 3-acetyldeoxynivalenol (3-ADON), 15-acetyldeoxynivalenol (15-ADON) and nivalenol producing F. graminearum strains in a time course study. Quantitative reverse transcription polymerase chain reaction revealed that the expression of all examined TRI gene transcripts initiated at 2 days post-inoculation (dpi), peaked at three to four dpi and gradually decreased at seven dpi. The early induction of TRI genes indicates that presence of high levels of TRI gene transcripts at early stages is important to initiate the biosynthetic pathway of DON and NIV. Comparison of gene expression among the three chemotypes showed that relative expression of TRI genes was higher in 3-ADON producing strains compared with 15-ADON and NIV strains. Comparatively higher levels of gene expression may contribute to the higher levels of DON produced by 3-ADON strains in infected grains.
Highlights
Fusarium head blight (FHB) is one of the major economically important fungal diseases in wheat, barley, corn, and other small grains worldwide
A similar transcript accumulation pattern was observed in the susceptible (S) cultivar Roblin, at 10 dpi there was a slight increase in transcript accumulation in 3-ADON1, 3-ADON2 and 15-ADON1 strains and gradually decreased at 14 dpi (Figure 1B)
The expression of most TRI genes required for trichothecene production in F. graminearum were strongly induced at early time points after infection (i.e., 2–4 dpi) and the expression levels gradually decreased at 7 dpi
Summary
Fusarium head blight (FHB) is one of the major economically important fungal diseases in wheat, barley, corn, and other small grains worldwide. Fusarium mycotoxins represent the largest group of mycotoxins, which contains more than 140 known metabolites such as trichothecenes, zearalenone and fumonisins (Yazar and Omurtag, 2008; Sobrova et al, 2010). Among these mycotoxins, trichothecenes are one of the major Fusarium mycotoxins synthesized mainly by the members in the Fusarium graminearum species complex (FGSC), F. culmorum, F. sprotrichioides and F. poae (Desjardins et al, 1993; Foroud and Eudes, 2009; Wang et al, 2011).
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