Abstract
The velvet protein, VeA, is involved in the regulation of diverse cellular processes. In this study, we explored functions of FgVeA in the wheat head blight pathogen, Fusarium graminearum,using a gene replacement strategy. The FgVEA deletion mutant exhibited a reduction in aerial hyphae formation, hydrophobicity, and deoxynivalenol (DON) biosynthesis. Deletion of FgVEA gene led to an increase in conidial production, but a delay in conidial germination. Pathogencity assays showed that the mutant was impaired in virulence on flowering wheat head. Sensitivity tests to various stresses exhibited that the FgVEA deletion mutant showed increased resistance to osmotic stress and cell wall-damaging agents, but increased sensitivity to iprodione and fludioxonil fungicides. Ultrastructural and histochemical analyses revealed that conidia of FgVeA deletion mutant contained an unusually high number of large lipid droplets, which is in agreement with the observation that the mutant accumulated a higher basal level of glycerol than the wild-type progenitor. Serial analysis of gene expression (SAGE) in the FgVEA mutant confirmed that FgVeA was involved in various cellular processes. Additionally, six proteins interacting with FgVeA were identified by yeast two hybrid assays in current study. These results indicate that FgVeA plays a critical role in a variety of cellular processes in F. graminearum.
Highlights
Fusarium graminearum Schwabe [teleomorph Gibberella zeae (Schwein.) Petch], a homothallic ascomycete, is the major causal agent of Fusarium head blight (FHB), which is a devastating disease of cereal crops worldwide [1]
Consistent with conserved N-terminal as well as variable C-terminal functions of the velvet proteins, in this study, we found some of the phenotypes in FgVEA mutant were similar to those reported in other fungi, while others were novel and unique to F. graminearum
The first study of VeA ortholog in other fungal species beyond the genus Aspergillus was conducted by Li et al for the plant pathogen F. verticillioides [13]
Summary
Fusarium graminearum Schwabe [teleomorph Gibberella zeae (Schwein.) Petch], a homothallic ascomycete, is the major causal agent of Fusarium head blight (FHB), which is a devastating disease of cereal crops worldwide [1]. A better understanding of regulation mechanisms of fungal development, virulence, and DON biosynthesis in F. graminearum will be essential to facilitate the development of efficient control strategies against FHB. The velvet protein encoded by VEA gene has been shown to be involved in the regulation of diverse cellular processes, including control of asexual and sexual development as well as secondary metabolisms in several fungal species [3,4]. It is interesting that in A. parasiticus, genetically related to A. nidulans, deletion of VEA resulted to a reduction of conidiation [8]. These results indicate that the role of VeA in sexual development varies significantly among different fungal species
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