Abstract
The homothallic ascomycete fungus Gibberella zeae is a plant pathogen that is found worldwide, causing Fusarium head blight (FHB) in cereal crops and ear rot of maize. Ascospores formed in fruiting bodies (i.e., perithecia) are hypothesized to be the primary inocula for FHB disease. Perithecium development is a complex cellular differentiation process controlled by many developmentally regulated genes. In this study, we selected a previously reported putative transcription factor containing the Myb DNA-binding domain MYT2 for an in-depth study on sexual development. The deletion of MYT2 resulted in a larger perithecium, while its overexpression resulted in a smaller perithecium when compared to the wild-type strain. These data suggest that MYT2 regulates perithecium size differentiation. MYT2 overexpression affected pleiotropic phenotypes including vegetative growth, conidia production, virulence, and mycotoxin production. Nuclear localization of the MYT2 protein supports its role as a transcriptional regulator. Transcriptional analyses of trichothecene synthetic genes suggest that MYT2 additionally functions as a suppressor for trichothecene production. This is the first study characterizing a transcription factor required for perithecium size differentiation in G. zeae, and it provides a novel angle for understanding sexual development in filamentous fungi.
Highlights
The homothallic ascomycete fungus Gibberella zeae is a worldwide plant pathogen that causes Fusarium head blight (FHB) in cereal crops and ear rot of maize [1]
After overwintering as perithecia or perithecia-associated hyphae formed on plant debris, the ascospores are forcibly discharge from mature perithecia during flowering season and are considered primary inocula [3,4,5,6]
Myb DNA-binding domain-containing transcription factor 2 (MYT2) has no orthologs in the species of the phyla Oomycota and Basidiomycota, but it is conserved in species of the subphylum Pezizomycotina of the Ascomycota, in Sordariomycetes (Figure 1A and B)
Summary
The homothallic ascomycete fungus Gibberella zeae (anamorph: Fusarium graminearum) is a worldwide plant pathogen that causes Fusarium head blight (FHB) in cereal crops and ear rot of maize [1]. This fungal infection leads to severe yield losses and the accumulation of mycotoxins, such as trichothecenes and zearalenone, which are harmful to humans and livestock [2]. The tips of ascogenous hyphae contain two nuclei that pair to form the dikaryotic state This dikaryotic mycelial phase is followed by karyogamy of two haploid nuclei, resulting in a diploid nucleus. The binucleate condition was eventually established in the ascogenous hyphae and first observed in the crosiers [4]
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