The Ultrastructure of Aphanomyces euteiches During Asexual Spore Formation

Zoosporogenesis in Aphanomyces euteiches was inhibited by increasing the osmotic water potential (ψπ) of the wash solution used to induce asexual reproduction. Mycelial protoplasm did not differentiate into primary spores when exposed to osmotica of glucose, mannose, fructose, sorbitol, sucrose, KCl, CaCl2, and polyethylene glycol (PEG) 4000 of ψπ ≤ −5.0 bars. Primary spores were formed in these osmotica at ψπ ≥ −4.0 bars, but they were not extruded from the sporangia until the ψπ ≥ −3.0 bars. Active zoospores were observed only at ψπ ≥ −2.0 bars and were most abundant at ψπ ≥ −0.5 bars. Osmotica of mannitol, i-erythritol, glycerol, and i-inositol did not completely suppress zoospore formation until the ψπ ≤ −7.0 bars, and primary spore cleavage occurred at ψπ as low as −11.0 bars. PEG-6000 and PEG-20 000 prevented primary spore formation at ψπ below −3.0 bars and −0.5 bars, respectively. The ψπ and turgor pressure (ψp) of mycelia exposed to various water potentials were also determined and found not to differ greatly between the various osmotica. The ψπ of vegetative mycelia was found to be about −8.0 bars, while that activated to form primary spores in the basal salt wash solution was −3.0 bars. As the ψπ of the solution decreased, so did the ψπ of the mycelia until the two were equal to about −14.0 bars, thus creating a zero ψp of the mycelia. Mechanisms for asexual spore formation and discharge are also discussed.

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Label-Free Quantitative Proteomics of Lysine Acetylome Identifies Substrates of Gcn5 in Magnaporthe oryzae Autophagy and Epigenetic Regulation

mSystems ◽

10.1128/msystems.00270-18 ◽

2018 ◽

Vol 3 (6) ◽

Cited By ~ 4

Author(s):

Meiling Liang ◽

Shulin Zhang ◽

Lihong Dong ◽

Yanjun Kou ◽

Chaoxiang Lin ◽

...

Keyword(s):

Epigenetic Regulation ◽

Magnaporthe Oryzae ◽

Posttranslational Modification ◽

Rice Blast ◽

Histone Acetyltransferase ◽

Rice Blast Fungus ◽

Spore Formation ◽

Content Type ◽

Autophagy Induction ◽

Asexual Spore

ABSTRACT The rice blast fungus Magnaporthe oryzae poses a great threat to global food security. During its conidiation (asexual spore formation) and appressorium (infecting structure) formation, autophagy is induced, serving glycogen breakdown or programmed cell death function, both essential for M. oryzae pathogenicity. Recently, we identified an M. oryzae histone acetyltransferase (HAT) Gcn5 as a key regulator in phototropic induction of autophagy and asexual spore formation while serving a cellular function other than autophagy induction during M. oryzae infection. To further understand the regulatory mechanism of Gcn5 on M. oryzae pathogenicity, we set out to identify more Gcn5 substrates by comparative acetylome between the wild-type (WT) and GCN5 overexpression (OX) mutant and between OX mutant and GCN5 deletion (knockout [KO]) mutant. Our results showed that Gcn5 regulates autophagy induction and other important aspects of fungal pathogenicity, including energy metabolism, stress response, cell toxicity and death, likely via both epigenetic regulation (histone acetylation) and posttranslational modification (nonhistone protein acetylation). IMPORTANCE Gcn5 is a histone acetyltransferase that was previously shown to regulate phototropic and starvation-induced autophagy in the rice blast fungus Magnaporthe oryzae, likely via modification on autophagy protein Atg7. In this study, we identified more potential substrates of Gcn5-mediated acetylation by quantitative and comparative acetylome analyses. By epifluorescence microscopy and biochemistry experiments, we verified that Gcn5 may regulate autophagy induction at both the epigenetic and posttranslational levels and regulate autophagic degradation of a critical metabolic enzyme pyruvate kinase (Pk) likely via acetylation. Overall, our findings reveal comprehensive posttranslational modification executed by Gcn5, in response to various external stimuli, to synergistically promote cellular differentiation in a fungal pathogen.

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Faculty Opinions recommendation of Septins are important for cell polarity, septation and asexual spore formation in Neurospora crassa and show different patterns of localisation at germ tube tips.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.724136257.793525622 ◽

2016 ◽

Author(s):

Meritxell Riquelme

Keyword(s):

Neurospora Crassa ◽

Cell Polarity ◽

Germ Tube ◽

Spore Formation ◽

Asexual Spore

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Septins Are Important for Cell Polarity, Septation and Asexual Spore Formation in Neurospora crassa and Show Different Patterns of Localisation at Germ Tube Tips

PLoS ONE ◽

10.1371/journal.pone.0063843 ◽

2013 ◽

Vol 8 (5) ◽

pp. e63843 ◽

Cited By ~ 30

Author(s):

Adokiye Berepiki ◽

Nick D. Read

Keyword(s):

Neurospora Crassa ◽

Cell Polarity ◽

Germ Tube ◽

Spore Formation ◽

Asexual Spore

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Mechanism for the Suppression of pea (Pisum sativum) Root Rot by Dinitroaniline Herbicides

Weed Science ◽

10.1017/s0043174500043812 ◽

1979 ◽

Vol 27 (2) ◽

pp. 195-201 ◽

Cited By ~ 2

Author(s):

J. R. Teasdale ◽

R. G. Harvey ◽

D. J. Hagedorn

Keyword(s):

Pisum Sativum ◽

Root Rot ◽

Solution Culture ◽

Spore Production ◽

Aphanomyces Euteiches ◽

Sensitive Stage ◽

Zoospore Production ◽

Asexual Spore ◽

Pea Roots ◽

Dinitroaniline Herbicides

Pea (Pisum sativumL. ‘Elf’) root rot suppression by dinitroaniline herbicides could not be explained by a direct effect on the host. Pre-incubation of pea roots with 0.1 ppmw of oryzalin (3,5-dinitro-N4,N4-dipropylsulfanilamide) or trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) in solution culture did not alter their resistance to root rot. Furthermore, 0.1 ppmw of oryzalin or trifluralin did not alter the exudation of electrolytes or α-amino compounds from pea roots. Most of the dinitroaniline herbicides significantly inhibited mycelial radial growth of pathogen,Aphanomyces euteichesDrechs., at 1.0 ppmw and inhibited asexual spore production at 0.1 to 1.0 ppmw. Dinitramine (N4,N4-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine), fluchloralin [N-(2-chloroethyl)-2,6-dinitro-N-propyl-4-(trifluoromethyl)aniline], and oryzalin inhibitedA. euteichesmycelial growth and asexual reproduction more effectively than the other dinitroaniline herbicides studied. The production of motile zoospores, the infecting propagule of the pathogen, was the most sensitive stage in the life cycle and was completely inhibited by 0.01 ppmw of all dinitroaniline herbicides tested. Since this concentration is below that estimated in the soil solution at registered rates of application, inhibition of motile zoospore production is sufficient to explain root rot suppression. Inhibition of pathogen motility resulted in a 2-week delay in the infection of pea roots. This delay allowed sufficient additional plant growth that the peas could better withstand the effects of subsequent disease development.

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A continuous flow system for inducing and observing asexual spore formation in Aphanomyces euteiches

Canadian Journal of Botany ◽

10.1139/b72-082 ◽

1972 ◽

Vol 50 (3) ◽

pp. 681-682 ◽

Cited By ~ 4

Author(s):

H. C. Hoch ◽

J. E. Mitchell

Keyword(s):

Liquid Medium ◽

Microscopic Observation ◽

Continuous Flow ◽

Flow System ◽

Vegetative State ◽

Extended Period ◽

Aphanomyces Euteiches ◽

Light Microscopic Observation ◽

Asexual Spore ◽

Cytological Changes

A technique is described that permits light microscopic observation of living hyphae in a liquid medium for an extended period of time. The procedure described was used to study cytological changes in hyphae of Aphanomyces euteiches during the transition from the vegetative state through the delineation of asexual spores and their extrusion from the sporangium apex.

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