Abstract
We previously characterized members of the Myb protein family, MYT1 and MYT2, in Fusarium graminearum. MYT1 and MYT2 are involved in female fertility and perithecium size, respectively. To expand knowledge of Myb proteins in F. graminearum, in this study, we characterized the functions of the MYT3 gene, which encodes a putative Myb-like transcription factor containing two Myb DNA-binding domains and is conserved in the subphylum Pezizomycotina of Ascomycota. MYT3 proteins were localized in nuclei during most developmental stages, suggesting the role of MYT3 as a transcriptional regulator. Deletion of MYT3 resulted in impairment of conidiation, germination, and vegetative growth compared to the wild type, whereas complementation of MYT3 restored the wild-type phenotype. Additionally, the Δmyt3 strain grew poorly on nitrogen-limited media; however, the mutant grew robustly on minimal media supplemented with ammonium. Moreover, expression level of nitrate reductase gene in the Δmyt3 strain was decreased in comparison to the wild type and complemented strain. On flowering wheat heads, the Δmyt3 strain exhibited reduced pathogenicity, which corresponded with significant reductions in trichothecene production and transcript levels of trichothecene biosynthetic genes. When the mutant was selfed, mated as a female, or mated as a male for sexual development, perithecia were not observed on the cultures, indicating that the Δmyt3 strain lost both male and female fertility. Taken together, these results demonstrate that MYT3 is required for pathogenesis and sexual development in F. graminearum, and will provide a robust foundation to establish the regulatory networks for all Myb-like proteins in F. graminearum.
Highlights
The homothallic ascomycete fungus Fusarium graminearum is a prominent plant pathogen that causes Fusarium head blight (FHB) on cereal crops and ear rot on maize [1,2], resulting in a severe reduction of crop yield and production of mycotoxins that are dangerous to animals and humans [3]
Of these Myb-like proteins, we found that MYT1 and MYT2 transcription factors are involved in female fertility and perithecium size, respectively [12,13]
As a series of MYT1 and MYT2, we aimed to expand the current knowledge of how Myb transcription factors regulate sexual development of F. graminearum, with an emphasis on the characterization of the gene involved in the formation of perithecia and ascospores
Summary
The homothallic ascomycete fungus Fusarium graminearum is a prominent plant pathogen that causes Fusarium head blight (FHB) on cereal crops and ear rot on maize [1,2], resulting in a severe reduction of crop yield and production of mycotoxins (e.g., trichothecenes and zearalenone) that are dangerous to animals and humans [3]. In the F. graminearum genome, 19 transcription factors encoding Myb-like proteins were identified at a previous work [11]. Of these Myb-like proteins, we found that MYT1 and MYT2 transcription factors are involved in female fertility and perithecium size, respectively [12,13]. Several deletion mutants of putative Myb transcription factors, including FGSG_01915, FGSG_02719, and FGSG_12781, in F. graminearum exhibited abnormality in sexual development [11]. These data suggest that the Myb transcription factors are required for normal sexual development of F. graminearum
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