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The Mitogen-Activated Protein Kinase Kinase VdPbs2 of Verticillium dahliae Regulates Microsclerotia Formation, Stress Response, and Plant Infection

View Article: PubMed Central - PubMed

ABSTRACT

Verticillium dahliae, a ubiquitous phytopathogenic fungus, forms resting structures, known as microsclerotia that play crucial roles in Verticillium wilt diseases. VdHog1, a mitogen-activated protein kinase (MAPK), controls microsclerotia formation, virulence, and stress response in V. dahliae. In this study, we present detailed evidence that the conserved upstream component of VdHog1, VdPbs2, is a key regulator of microsclerotia formation, oxidative stress and fungicide response and plant virulence in V. dahliae. We identified VdPbs2, homologous to the yeast MAPK kinase Pbs2. Similar to the VdHog1 deletion mutant, VdPbs2 deletion strains exhibited delayed melanin synthesis and reduced formation of microsclerotia. When exposed to stresses, VdPbs2 mutants were more sensitive than the wild type to osmotic agents and peroxide, but more resistant to inhibitors of cell wall synthesis and some fungicides. Finally, VdPbs2 deletion mutants exhibited reduced virulence on smoke tree and tobacco seedlings. When taken together, we implicate that VdPbs2 and VdHog1 function in a cascade that regulates microsclerotia formation and virulence, but not all VdHog1 dependent functions are VdPbs2 regulated. This study thus provides novel insights into the signal transduction mechanisms that regulate microsclerotia formation and pathogenesis in this fungus.

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VdPbs2 deletion mutants exhibit distinct responses to different fungicides. (A) The ΔVdPbs2 and ΔVdHog1 mutants showed enhanced resistance to fludioxonil and iprodione. Conidial suspension (105/ml and 106 /ml) of the wild type, ΔVdPbs2 and ΔVdHog1, and the the ΔVdPbs2/Pbs2 were spotted on CM media with the indicated concentration of fludioxonil and iprodione, respectively. (B) The ΔVdPbs2 and ΔVdHog1 mutants exhibited more sensitivity to chlorothalonil and difenoconazole. Conidial suspension (105/ml and 106 /ml) of the above strains were spotted on CM media with the indicated concentration of chlorothalonil and difenoconazole, respectively. (C) Growth rate of the above strains on CM containing with the indicated concentration of fludioxonil and iprodione, respectively. Error bar represents standard deviation. Asterisk indicates significant difference at P < 0.01.
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Figure 6: VdPbs2 deletion mutants exhibit distinct responses to different fungicides. (A) The ΔVdPbs2 and ΔVdHog1 mutants showed enhanced resistance to fludioxonil and iprodione. Conidial suspension (105/ml and 106 /ml) of the wild type, ΔVdPbs2 and ΔVdHog1, and the the ΔVdPbs2/Pbs2 were spotted on CM media with the indicated concentration of fludioxonil and iprodione, respectively. (B) The ΔVdPbs2 and ΔVdHog1 mutants exhibited more sensitivity to chlorothalonil and difenoconazole. Conidial suspension (105/ml and 106 /ml) of the above strains were spotted on CM media with the indicated concentration of chlorothalonil and difenoconazole, respectively. (C) Growth rate of the above strains on CM containing with the indicated concentration of fludioxonil and iprodione, respectively. Error bar represents standard deviation. Asterisk indicates significant difference at P < 0.01.

Mentions: VdHog1 deletion mutant is highly resistant to the fungicide fludioxonil (Wang et al., 2016). To determine if deletion of VdPbs2 affects the response to fungicides, we tested the sensitivity of the ΔVdPbs2 mutant to various fungicides. Similar to the response of the ΔVdHog1 mutant to fungicides, the ΔVdPbs2 mutant exhibited enhanced resistance to fludioxonil and iprodione and increased sensitivity to chlorothalonil and difenoconazole, respectively, when compared with the wild type and the ΔVdPbs2/Pbs2 strain (Figure 6), suggesting that VdPbs2 is involved in accumulation of osmoprotectant molecules of fungal cell in the response to fungicidal compounds.


The Mitogen-Activated Protein Kinase Kinase VdPbs2 of Verticillium dahliae Regulates Microsclerotia Formation, Stress Response, and Plant Infection
VdPbs2 deletion mutants exhibit distinct responses to different fungicides. (A) The ΔVdPbs2 and ΔVdHog1 mutants showed enhanced resistance to fludioxonil and iprodione. Conidial suspension (105/ml and 106 /ml) of the wild type, ΔVdPbs2 and ΔVdHog1, and the the ΔVdPbs2/Pbs2 were spotted on CM media with the indicated concentration of fludioxonil and iprodione, respectively. (B) The ΔVdPbs2 and ΔVdHog1 mutants exhibited more sensitivity to chlorothalonil and difenoconazole. Conidial suspension (105/ml and 106 /ml) of the above strains were spotted on CM media with the indicated concentration of chlorothalonil and difenoconazole, respectively. (C) Growth rate of the above strains on CM containing with the indicated concentration of fludioxonil and iprodione, respectively. Error bar represents standard deviation. Asterisk indicates significant difference at P < 0.01.
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Figure 6: VdPbs2 deletion mutants exhibit distinct responses to different fungicides. (A) The ΔVdPbs2 and ΔVdHog1 mutants showed enhanced resistance to fludioxonil and iprodione. Conidial suspension (105/ml and 106 /ml) of the wild type, ΔVdPbs2 and ΔVdHog1, and the the ΔVdPbs2/Pbs2 were spotted on CM media with the indicated concentration of fludioxonil and iprodione, respectively. (B) The ΔVdPbs2 and ΔVdHog1 mutants exhibited more sensitivity to chlorothalonil and difenoconazole. Conidial suspension (105/ml and 106 /ml) of the above strains were spotted on CM media with the indicated concentration of chlorothalonil and difenoconazole, respectively. (C) Growth rate of the above strains on CM containing with the indicated concentration of fludioxonil and iprodione, respectively. Error bar represents standard deviation. Asterisk indicates significant difference at P < 0.01.
Mentions: VdHog1 deletion mutant is highly resistant to the fungicide fludioxonil (Wang et al., 2016). To determine if deletion of VdPbs2 affects the response to fungicides, we tested the sensitivity of the ΔVdPbs2 mutant to various fungicides. Similar to the response of the ΔVdHog1 mutant to fungicides, the ΔVdPbs2 mutant exhibited enhanced resistance to fludioxonil and iprodione and increased sensitivity to chlorothalonil and difenoconazole, respectively, when compared with the wild type and the ΔVdPbs2/Pbs2 strain (Figure 6), suggesting that VdPbs2 is involved in accumulation of osmoprotectant molecules of fungal cell in the response to fungicidal compounds.

View Article: PubMed Central - PubMed

ABSTRACT

Verticillium dahliae, a ubiquitous phytopathogenic fungus, forms resting structures, known as microsclerotia that play crucial roles in Verticillium wilt diseases. VdHog1, a mitogen-activated protein kinase (MAPK), controls microsclerotia formation, virulence, and stress response in V. dahliae. In this study, we present detailed evidence that the conserved upstream component of VdHog1, VdPbs2, is a key regulator of microsclerotia formation, oxidative stress and fungicide response and plant virulence in V. dahliae. We identified VdPbs2, homologous to the yeast MAPK kinase Pbs2. Similar to the VdHog1 deletion mutant, VdPbs2 deletion strains exhibited delayed melanin synthesis and reduced formation of microsclerotia. When exposed to stresses, VdPbs2 mutants were more sensitive than the wild type to osmotic agents and peroxide, but more resistant to inhibitors of cell wall synthesis and some fungicides. Finally, VdPbs2 deletion mutants exhibited reduced virulence on smoke tree and tobacco seedlings. When taken together, we implicate that VdPbs2 and VdHog1 function in a cascade that regulates microsclerotia formation and virulence, but not all VdHog1 dependent functions are VdPbs2 regulated. This study thus provides novel insights into the signal transduction mechanisms that regulate microsclerotia formation and pathogenesis in this fungus.

No MeSH data available.