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Crosstalk between SNF1 pathway and the peroxisome-mediated lipid metabolism in Magnaporthe oryzae.

Zeng XQ, Chen GQ, Liu XH, Dong B, Shi HB, Lu JP, Lin F - PLoS ONE (2014)

Bottom Line: And the upstream kinases, MoSak1 and MoTos3, play unequal roles in SNF1 activation with a clear preference to MoSak1 over MoTos3.Meanwhile, the mutant lacking both of them exhibited a severe phenotype comparable to ΔMosnf1, uncovering a cooperative relationship between MoSak1 and MoTos3.Taken together, our data indicate that the SNF1 pathway is required for fungal development and facilitates pathogenicity by its contribution to peroxisomal maintenance and lipid metabolism in M. oryzae.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory for Rice Biology, Biotechnology Institute, Zhejiang University, Hangzhou, China.

ABSTRACT
The SNF1/AMPK pathway has a central role in response to nutrient stress in yeast and mammals. Previous studies on SNF1 function in phytopathogenic fungi mostly focused on the catalytic subunit Snf1 and its contribution to the derepression of cell wall degrading enzymes (CWDEs). However, the MoSnf1 in Magnaporthe oryzae was reported not to be involved in CWDEs regulation. The mechanism how MoSnf1 functions as a virulence determinant remains unclear. In this report, we demonstrate that MoSnf1 retains the ability to respond to nutrient-free environment via its participation in peroxisomal maintenance and lipid metabolism. Observation of GFP-tagged peroxisomal targeting signal-1 (PTS1) revealed that the peroxisomes of ΔMosnf1 were enlarged in mycelia and tended to be degraded before conidial germination, leading to the sharp decline of peroxisomal amount during appressorial development, which might impart the mutant great retard in lipid droplets mobilization and degradation. Consequently, ΔMosnf1 exhibited inability to maintain normal appressorial cell wall porosity and turgor pressure, which are key players in epidermal infection process. Exogenous glucose could partially restore the appressorial function and virulence of ΔMosnf1. Toward a further understanding of SNF1 pathway, the β-subunit MoSip2, γ-subunit MoSnf4, and two putative Snf1-activating kinases, MoSak1 and MoTos3, were additionally identified and characterized. Here we show the mutants ΔMosip2 and ΔMosnf4 performed multiple disorders as ΔMosnf1 did, suggesting the complex integrity is essential for M. oryzae SNF1 kinase function. And the upstream kinases, MoSak1 and MoTos3, play unequal roles in SNF1 activation with a clear preference to MoSak1 over MoTos3. Meanwhile, the mutant lacking both of them exhibited a severe phenotype comparable to ΔMosnf1, uncovering a cooperative relationship between MoSak1 and MoTos3. Taken together, our data indicate that the SNF1 pathway is required for fungal development and facilitates pathogenicity by its contribution to peroxisomal maintenance and lipid metabolism in M. oryzae.

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Penetration assay on barley epidermal cells.Barley leaves were inoculated with conidial suspensions supplemented without (A) or with (B) 2.5% glucose for 48 h, and then decolored by methanol before observation. A, appressorium; C, conidium; IH, invasive hyphae. Bars  = 15 µm. (C) Percentage of appressoria capable of penetration was counted at 48 hpi, and the results were presented as means and standard deviations.
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pone-0103124-g010: Penetration assay on barley epidermal cells.Barley leaves were inoculated with conidial suspensions supplemented without (A) or with (B) 2.5% glucose for 48 h, and then decolored by methanol before observation. A, appressorium; C, conidium; IH, invasive hyphae. Bars  = 15 µm. (C) Percentage of appressoria capable of penetration was counted at 48 hpi, and the results were presented as means and standard deviations.

Mentions: To further test the appressorial function, penetration and invasive growth were microscopically observed after inoculating barley leaves with conidial suspensions from WT and the mutants. Consistent with the pathogenicity assay, the penetration rates of ΔMosnf4 and ΔMosak1 (11.4% and 39.8%, respectively) were strongly compromised when compared to Guy11 (77.0%) at 48 hpi (Figure 10C), although some mutant appressoria developed aggressive invasive hyphae (Figure 10A). The rate of appressoria forming infectious hyphae in ΔMotos3 (70.8%) was comparable to WT (Figure 10C). Whereas ΔMosnf1, ΔMosak1ΔMotos3, and the majority of ΔMosip2 (98.3%) appressoria were incapable of penetrating barley epidermal cells at 48 hpi (Figure 10A and 10C), revealing that their reduced virulence was the result of perturbed appressorial function.


Crosstalk between SNF1 pathway and the peroxisome-mediated lipid metabolism in Magnaporthe oryzae.

Zeng XQ, Chen GQ, Liu XH, Dong B, Shi HB, Lu JP, Lin F - PLoS ONE (2014)

Penetration assay on barley epidermal cells.Barley leaves were inoculated with conidial suspensions supplemented without (A) or with (B) 2.5% glucose for 48 h, and then decolored by methanol before observation. A, appressorium; C, conidium; IH, invasive hyphae. Bars  = 15 µm. (C) Percentage of appressoria capable of penetration was counted at 48 hpi, and the results were presented as means and standard deviations.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4121083&req=5

pone-0103124-g010: Penetration assay on barley epidermal cells.Barley leaves were inoculated with conidial suspensions supplemented without (A) or with (B) 2.5% glucose for 48 h, and then decolored by methanol before observation. A, appressorium; C, conidium; IH, invasive hyphae. Bars  = 15 µm. (C) Percentage of appressoria capable of penetration was counted at 48 hpi, and the results were presented as means and standard deviations.
Mentions: To further test the appressorial function, penetration and invasive growth were microscopically observed after inoculating barley leaves with conidial suspensions from WT and the mutants. Consistent with the pathogenicity assay, the penetration rates of ΔMosnf4 and ΔMosak1 (11.4% and 39.8%, respectively) were strongly compromised when compared to Guy11 (77.0%) at 48 hpi (Figure 10C), although some mutant appressoria developed aggressive invasive hyphae (Figure 10A). The rate of appressoria forming infectious hyphae in ΔMotos3 (70.8%) was comparable to WT (Figure 10C). Whereas ΔMosnf1, ΔMosak1ΔMotos3, and the majority of ΔMosip2 (98.3%) appressoria were incapable of penetrating barley epidermal cells at 48 hpi (Figure 10A and 10C), revealing that their reduced virulence was the result of perturbed appressorial function.

Bottom Line: And the upstream kinases, MoSak1 and MoTos3, play unequal roles in SNF1 activation with a clear preference to MoSak1 over MoTos3.Meanwhile, the mutant lacking both of them exhibited a severe phenotype comparable to ΔMosnf1, uncovering a cooperative relationship between MoSak1 and MoTos3.Taken together, our data indicate that the SNF1 pathway is required for fungal development and facilitates pathogenicity by its contribution to peroxisomal maintenance and lipid metabolism in M. oryzae.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory for Rice Biology, Biotechnology Institute, Zhejiang University, Hangzhou, China.

ABSTRACT
The SNF1/AMPK pathway has a central role in response to nutrient stress in yeast and mammals. Previous studies on SNF1 function in phytopathogenic fungi mostly focused on the catalytic subunit Snf1 and its contribution to the derepression of cell wall degrading enzymes (CWDEs). However, the MoSnf1 in Magnaporthe oryzae was reported not to be involved in CWDEs regulation. The mechanism how MoSnf1 functions as a virulence determinant remains unclear. In this report, we demonstrate that MoSnf1 retains the ability to respond to nutrient-free environment via its participation in peroxisomal maintenance and lipid metabolism. Observation of GFP-tagged peroxisomal targeting signal-1 (PTS1) revealed that the peroxisomes of ΔMosnf1 were enlarged in mycelia and tended to be degraded before conidial germination, leading to the sharp decline of peroxisomal amount during appressorial development, which might impart the mutant great retard in lipid droplets mobilization and degradation. Consequently, ΔMosnf1 exhibited inability to maintain normal appressorial cell wall porosity and turgor pressure, which are key players in epidermal infection process. Exogenous glucose could partially restore the appressorial function and virulence of ΔMosnf1. Toward a further understanding of SNF1 pathway, the β-subunit MoSip2, γ-subunit MoSnf4, and two putative Snf1-activating kinases, MoSak1 and MoTos3, were additionally identified and characterized. Here we show the mutants ΔMosip2 and ΔMosnf4 performed multiple disorders as ΔMosnf1 did, suggesting the complex integrity is essential for M. oryzae SNF1 kinase function. And the upstream kinases, MoSak1 and MoTos3, play unequal roles in SNF1 activation with a clear preference to MoSak1 over MoTos3. Meanwhile, the mutant lacking both of them exhibited a severe phenotype comparable to ΔMosnf1, uncovering a cooperative relationship between MoSak1 and MoTos3. Taken together, our data indicate that the SNF1 pathway is required for fungal development and facilitates pathogenicity by its contribution to peroxisomal maintenance and lipid metabolism in M. oryzae.

Show MeSH
Related in: MedlinePlus