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Hexokinase plays a critical role in deoxynivalenol (DON) production and fungal development in Fusarium graminearum

Zhang, Leigang, Li, Baicun, Zhang, Yu, Jia, Xiaojing, Zhou, Mingguo
Molecular plant pathology 2016 v.17 no.1 pp. 16-28
Fusarium graminearum, Fusarium head blight, biosynthesis, carbendazim, conidiation, corn, deoxynivalenol, fungi, gene expression regulation, gene overexpression, gene targeting, genes, hexokinase, mutants, pathogens, phylogeny, pyruvic acid, sexual reproduction, stigma, transcription (genetics), vegetative growth, virulence, wheat
Fusarium graminearum, the causal agent of Fusarium head blight, is a common pathogen on small grain cereals worldwide and produces various trichothecenes [deoxynivalenol (DON) is predominant] during infection. A previous study has revealed that DON production is positively correlated with the occurrence of carbendazim (MBC) resistance. Here, we identified and characterized two putative genes encoding hexokinase in F. graminearum (FgHXK1 and FgHXK2), which is a rate‐limiting enzyme in DON biosynthesis. The expression level of hexokinase genes and the production of pyruvate, which is the precursor of DON, were up‐regulated in the MBC‐resistant strain, indicating that hexokinase genes might be involved in increased DON production. Phylogenetic and comparative analyses indicated that FgHXK1 was the predominant hexokinase gene. Gene disruption showed that ΔFgHXK1 severely affected DON production, indicating that FgHXK1 played a role in the regulation of DON biosynthesis. Morphological characterization showed that ΔFgHXK1 led to inhibited vegetative growth and conidiation. Sensitivity tests to MBC and various stresses indicated that both ΔFgHXK1 and ΔFgHXK2 mutants showed no significant difference from parental strains. Pathogencity assays showed that ΔFgHXK1 mutants lost virulence on wheat head and corn stigma; however, they showed no change in sexual reproduction. The FgHXK1‐overexpressing transformants were obtained subsequently. Their pyruvate and DON production was confirmed to be increased, indicating that FgHXK1 positively regulated DON biosynthesis. Although additional defects appeared in overexpression mutants, MBC sensitivity showed no change. All of the results indicated that the transcriptional level of FgHXK1 regulated DON biosynthesis, but showed no direct relationship with MBC resistance.