Yingzi Yun

Zhejiang University, Hang-hsien, Zhejiang Sheng, China

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Publications (9)35.54 Total impact

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    ABSTRACT: The ergosterol biosynthesis pathway is well characterized in Saccharomyces cerevisiae, while little is known about the pathway in filamentous fungi. In this study, we isolated and genetically documented biological functions of FgErg3 and FgErg5, which are located upstream of FgErg4, the enzyme catalyzing the final step of ergosterol synthesis in Fusarium graminearum. Our results demonstrated that F. graminearum contains two paralogous FgERG3 and two FgERG5 genes. FgErg3, but not FgErg5, is involved in ergosterol biosynthesis. Double deletion mutants of FgERG3 alleles or the double deletion mutants of FgERG5 alleles showed decreased conidiation and produced abnormal conidia. Fungicide susceptibility tests revealed that FgERG3 and FgERG5 mutants have increased resistance towards triadimefon. However, FgERG3 mutants exhibited increased susceptibility to tebuconazole as well as increased susceptibility to oxidative stress, paraquat and to Mg(2+). Pathogenicity tests showed that the FgERG3 and FgERG5 double deletion mutant displayed dramatically attenuated virulence although they were able to successfully colonize flowering wheat head. In addition, complementation of FgERG3 and FgERG5 genes into S. cerevisiae partially rescued the susceptibility of S. cerevisiae ERG3 and ERG5 deletion mutants towards hydroxyurea and caffeine. Taken together, our results indicate that FgERG3 and FgERG5 play a crucial role in vegetative differentiation, resistance to fungicides and virulence in F. graminearum. FgErg3 alleles, but not FgErg5 alleles, are required for ergosterol biosynthesis in the filamentous fungus F. graminearum.
    Fungal Genetics and Biology 04/2014; · 3.26 Impact Factor
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    ABSTRACT: The target of rapamycin (TOR) signaling pathway plays critical roles in controlling cell growth in a variety of eukaryotes. However, the contribution of this pathway in regulating virulence of plant pathogenic fungi is unknown.We identified and characterized nine genes encoding components of the TOR pathway in Fusarium graminearum. Biological, genetic and biochemical functions of each component were investigated.The FgFkbp12-rapamycin complex binds to the FgTor kinase. The type 2A phosphatases FgPp2A, FgSit4 and FgPpg1 were found to interact with FgTap42, a downstream component of FgTor. Among these, we determined that FgPp2A is likely to be essential for F. graminearum survival, and FgSit4 and FgPpg1 play important roles in cell wall integrity by positively regulating the phosphorylation of FgMgv1, a key MAP kinase in the cell wall integrity pathway. In addition, the FgPpg1 interacting protein, FgTip41, is involved in regulating mycelial growth and virulence. Notably, FgTip41 does not interact with FgTap42 but with FgPpg1, suggesting the existence of FgTap42:FgPpg1:FgTip41 heterotrimer in F. graminearum, a complex not observed in the yeast model.Collectively, we defined a genetic regulatory framework that elucidates how the TOR pathway regulates virulence and vegetative development in F. graminearum.
    New Phytologist 03/2014; · 6.74 Impact Factor
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    ABSTRACT: The ergosterol biosynthesis pathway is well characterized in Saccharomyces cerevisiae, while little is known about the pathway in filamentous fungi. In this study, we isolated and genetically documented biological functions of FgErg3 and FgErg5, which are located upstream of FgErg4, the enzyme catalyzing the final step of ergosterol synthesis in Fusarium graminearum. Our results demonstrated that F. graminearum contains two paralogous FgERG3 and two FgERG5 genes. FgErg3, but not FgErg5, is involved in ergosterol biosynthesis. Double deletion mutants of FgERG3 alleles or the double deletion mutants of FgERG5 alleles showed decreased conidiation and produced abnormal conidia. Fungicide susceptibility tests revealed that FgERG3 and FgERG5 mutants have increased resistance towards triadimefon. However, FgERG3 mutants exhibited increased susceptibility to tebuconazole as well as increased susceptibility to oxidative stress, paraquat and to Mg2+. Pathogenicity tests showed that the FgERG3 and FgERG5 double deletion mutant displayed dramatically attenuated virulence although they were able to successfully colonize flowering wheat head. In addition, complementation of FgERG3 and FgERG5 genes into S. cerevisiae partially rescued the susceptibility of S. cerevisiae ERG3 and ERG5 deletion mutants towards hydroxyurea and caffeine. Taken together, our results indicate that FgERG3 and FgERG5 play a crucial role in vegetative differentiation, resistance to fungicides and virulence in F. graminearum. FgErg3 alleles, but not FgErg5 alleles, are required for ergosterol biosynthesis in the filamentous fungus F. graminearum.
    Fungal Genetics and Biology 01/2014; · 3.26 Impact Factor
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    ABSTRACT: Mitogen-activated protein (MAP) kinases play crucial roles in regulating fungal development, growth, and pathogenicity, and in responses to the environment. In this study, we characterized a MAP kinase kinase FgMkk1 in Fusarium graminearum, the causal agent of wheat head blight. Phenotypic analyses of the FgMKK1 mutant (ΔFgMKK1) showed that FgMkk1 is involved in the regulation of hyphal growth, pigmentation, conidiation, deoxynivalenol biosynthesis, and virulence of F. graminearum. ΔFgMKK1 also showed increased sensitivity to cell wall-damaging agents, and to osmotic and oxidative stresses, but exhibited decreased sensitivity to the fungicides iprodione and fludioxonil. In addition, the mutant revealed increased sensitivity to a biocontrol agent, Trichoderma atroviride. Western blot assays revealed that FgMkk1 positively regulates phosphorylation of the MAK kinases Mgv1 and FgOs-2, the key component in the cell wall integrity (CWI) and high-osmolarity glycerol (HOG) signaling pathway, respectively. Yeast two-hybrid assay indicated that Mgv1 interacts with a transcription factor FgRlm1. The FgRLM1 mutant (ΔFgRLM1) showed increased sensitivity to cell wall-damaging agents, and exhibited decreased virulence. Taken together, our data indicated that FgMkk1 is an upstream component of Mgv1 and FgOs-2, and regulates vegetative differentiation, multiple stress response and virulence via the CWI and HOG signaling pathways. FgRlm1 may be a downstream component of Mgv1 in the CWI pathway in F. graminearum.
    Environmental Microbiology 11/2013; · 5.76 Impact Factor
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    ABSTRACT: The velvet complex containing VeA, VelB and LaeA has been showed to play critical roles in the regulation of secondary metabolism and diverse cellular processes in Aspergillus spp. In this study, we identified FgVelB, a homolog of Aspergillus nidulans VelB, from Fusarium graminearum using the BLASTP program. Disruption of FgVELB gene led to several phenotypic defects, including suppression of aerial hyphae formation, reduced hyphal hydrophobicity and highly increased conidiation. The mutant showed increased resistance to osmotic stress and cell wall-damaging agents, which may be related to a high level of glycerol accumulation in the mutant. Additionally, the mutant exhibited increased sensitivity to the phenylpyrrole fungicide fludioxonil. Ultrastructural and histochemical analyses revealed that conidia of FgVELB deletion mutant contained numerous lipid droplets. Pathogenicity assays showed FgVELB deletion mutant was impaired in virulence on flowering wheat head, which is consistent with the observation that FgVelB is involved in the regulation of deoxynivalenol biosynthesis in F. graminearum. All of the defects were restored by genetic complementation of the mutant with wild-type FgVELB gene. Yeast two hybrid assays showed that FgVelB does not interact with FgVeA. Taken together, results of this study indicated that FgVelB plays a critical role in the regulation of various cellular processes in F. graminearum.
    Fungal Genetics and Biology 06/2012; 49(8):653-62. · 3.26 Impact Factor
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    ABSTRACT: Wheat take-all caused by Gaeumannomyces graminis var. tritici (Ggt) has become an emerging threat to wheat production in the last few years. Silthiofam is very effective against Ggt, and recently it has been widely used for the control of take-all in China. However, farmers have noted a decline in control efficacy with this compound in some wheat fields, suggesting that the pathogen may have developed resistance to silthiofam. Of the 66 Ggt isolates collected from different locations in China, 27 were resistant to silthiofam. There was no cross-resistance between silthiofam and tecuconazole or difenoconazole. The effectiveness of silthiofam in controlling take-all was compromised on wheat inoculated with silthiofam-resistant isolates. Based on the DNA fingerprinting generated by microsatellite PCR, two predominant genetic clusters were found among these isolates and were clearly associated with the sensitivity to silthiofam. Silthiofam has a high risk in the development of resistance in Ggt. Tebuconazole and difenoconazole show great potential for control of take-all on wheat. Results from this study provide useful information for take-all control and the management of fungicide resistance.
    Pest Management Science 01/2012; 68(8):1156-63. · 2.59 Impact Factor
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    ABSTRACT: Response regulator (RR) proteins are core elements of the high-osmolarity glycerol (HOG) pathway, which plays an important role in the adaptation of fungi to a variety of environmental stresses. In this study, we constructed deletion mutants of two putative RR genes, FgRRG-1 and FgRRG-2, which are orthologues of Neurospora crassa RRG-1 and RRG-2, respectively. The FgRRG-1 deletion mutant (ΔFgRrg1-6) showed increased sensitivity to osmotic stress mediated by NaCl, KCl, sorbitol or glucose, and to metal cations Li(+) , Ca(2+) and Mg(2+) . The mutant, however, was more resistant than the parent isolate to dicarboximide and phenylpyrrole fungicides. Inoculation tests showed that the mutant exhibited decreased virulence on wheat heads. Quantitative real-time polymerase chain reaction assays indicated that the expression of FgOS-2, the putative downstream gene of FgRRG-1, was decreased significantly in ΔFgRrg1-6. All of the defects were restored by genetic complementation of ΔFgRrg1-6 with the wild-type FgRRG-1 gene. Different from the FgRRG-1 deletion mutant, FgRRG-2 deletion mutants were morphologically indistinguishable from the wild-type progenitor in virulence and in sensitivity to the dicarboximide fungicide iprodione and osmotic stresses. These results indicate that the RR FgRrg-1 of F. graminearum is involved in the osmotic stress response, pathogenicity and sensitivity to dicarboximide and phenylpyrrole fungicides and metal cations.
    Molecular Plant Pathology 06/2011; 12(5):425-36. · 3.88 Impact Factor
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    ABSTRACT: Fusarium graminearum, the causal agent of wheat head blight, shows intrinsic resistance to amine fungicides. It is commonly accepted that the amines target sterol C-14 reductase and sterol Δ(8)-Δ(7) isomerase of ergosterol biosynthesis, encoded by the genes ERG24 and ERG2, respectively. Analysis of the genome sequence of F. graminearum revealed that the fungus contains two paralogous FgERG24 genes (FgERG24A and FgERG24B), which are homologous to the ERG24 of Saccharomyces cerevisiae. In this study, we disrupted FgERG24A and FgERG24B in F. graminearum. Compared to the wild-type strain HN9-1, FgERG24A and FgERG24B deletion mutants did not show recognizable phenotypic changes in mycelial growth on potato dextrose agar or in virulence on wheat heads. HPLC analysis showed that the amount of ergosterol in FgERG24A or FgERG24B deletion mutants was not significantly different from that in the wild-type strain. These results indicate that neither of the two genes is essential for growth, pathogenicity or ergosterol biosynthesis in F. graminearum. FgERG24B deletion mutants exhibited significantly increased sensitivity to amine fungicides, including tridemorph, fenpropidin and spiroxamine, but not to non-amine fungicides. In contrast, FgERG24A deletion mutants did not show changed sensitivity to any amine tested. The resistance of the FgERG24B deletion mutant to amines was restored by genetic complementation of the mutant with wild-type FgERG24B. These results indicate that FgERG24B controls the intrinsic resistance of F. graminearum to amines. The finding of this study provides new insights into amine resistance in filamentous fungi.
    Microbiology 03/2011; 157(Pt 6):1665-75. · 3.06 Impact Factor
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    ABSTRACT: Type 2C protein phosphatases (PP2Cs) play important roles in regulating many biological processes in eukaryotes. Currently, little is known about functions of PP2Cs in filamentous fungi. The causal agent of wheat head blight, Fusarium graminearum, contains seven putative PP2C genes, FgPTC1, -3, -5, -5R, -6, -7 and -7R. In order to investigate roles of these PP2Cs, we constructed deletion mutants for all seven PP2C genes in this study. The FgPTC3 deletion mutant (ΔFgPtc3-8) exhibited reduced aerial hyphae formation and deoxynivalenol (DON) production, but increased production of conidia. The mutant showed increased resistance to osmotic stress and cell wall-damaging agents on potato dextrose agar plates. Pathogencity assays showed that ΔFgPtc3-8 is unable to infect flowering wheat head. All of the defects were restored when ΔFgPtc3-8 was complemented with the wild-type FgPTC3 gene. Additionally, the FgPTC3 partially rescued growth defect of a yeast PTC1 deletion mutant under various stress conditions. Ultrastructural and histochemical analyses showed that conidia of ΔFgPtc3-8 contained an unusually high number of large lipid droplets. Furthermore, the mutant accumulated a higher basal level of glycerol than the wild-type progenitor. Quantitative real-time PCR assays showed that basal expression of FgOS2, FgSLT2 and FgMKK1 in the mutant was significantly higher than that in the wild-type strain. Serial analysis of gene expression in ΔFgPtc3-8 revealed that FgPTC3 is associated with various metabolic pathways. In contrast to the FgPTC3 mutant, the deletion mutants of FgPTC1, FgPTC5, FgPTC5R, FgPTC6, FgPTC7 or FgPTC7R did not show aberrant phenotypic features when grown on PDA medium or inoculated on wheat head. These results indicate FgPtc3 is the key PP2C that plays a critical role in a variety of cellular and biological functions, including cell wall integrity, lipid and secondary metabolisms, and virulence in F. graminearum.
    PLoS ONE 01/2011; 6(9):e25311. · 3.73 Impact Factor