Mannitol metabolism in the phytopathogenic fungus Alternaria alternata

The phytopathogenic fungus Alternaria alternata f. sp. lycopersici produces AAL toxins required to colonize susceptible tomato (Lycopersicon esculentum) plants. AAL toxins and fumonisins of the unrelated fungus Fusarium moniliforme are sphinganine-analog mycotoxins (SAMs), which are toxic for some plant species and mammalian cell lines. Insensitivity of tomato to SAMs is determined by the Alternaria stem canker gene 1 (Asc-1), and sensitivity is associated with a mutated Asc-1. We show that SAM-sensitive species occur at a low frequency in the Nicotiana genus and that candidate Asc-1 homologs are still present in those species. In Nicotiana spp., SAM-sensitivity and insensitivity also is mediated by a single codominant locus, suggesting that SAM-sensitive genotypes are host for A. alternata f. sp. lycopersici. Nicotiana umbratica plants homozygous for SAM-sensitivity are indeed susceptible to A. alternata f. sp. lycopersici. In contrast, SAM-sensitive genotypes of Nicotiana spegazzinii, Nicotiana acuminata var. acuminata, Nicotiana bonariensis, and Nicotiana langsdorffii are resistant to A. alternata f. sp. lycopersici infection concomitant with localized cell death. Additional (nonhost) resistance mechanisms to A. alternata f. sp. lycopersici that are not based on an insensitivity to SAMs are proposed to be present in Nicotiana species.

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Copper tolerance, protein and catalytic activity in phytopathogenic fungus Alternaria alternata

Global NEST Journal ◽

10.30955/gnj.001513 ◽

2015 ◽

Vol 17 (4) ◽

pp. 664-672 ◽

Cited By ~ 5

Keyword(s):

Alternaria Alternata ◽

Catalase Activity ◽

Metal Accumulation ◽

Metal Tolerance ◽

Copper Tolerance ◽

Phytopathogenic Fungus ◽

Copper Salts ◽

Growth Physiology ◽

Maximum Inhibition

<div> In vitro tolerance of soil borne phytopathogenic fungus i.e. Alternaria alternata in terms of growth, physiology and metal uptake capacity against different doses of copper [Cu(II)] metal was assessed. In preliminary growth experiments, nitrate, chloride and sulphate of Cu(II) were amended in seven different concentrations viz. 25, 50, 75, 80, 85, 90 and 100 ppm in nutritive agar medium along with fungus inoculum. Amongst three salts, the maximum inhibition in radial growth of the fungus was observed with increasing concentrations of copper salts in order of: CuSO4> CuNO3> CuCl2. Further trials were conducted in nutritive broth with four different concentrations (25, 50, 75 and 100 ppm) of copper sulphate to assess growth inhibition, metal accumulation, protein and catalase activity in the fungus biomass. It was found that fungus dry biomass was significantly declined by 70-99% along with net metal accumulation of 40% with increasing metal concentrations. Total protein contents and catalase activity was considerably increased up to 2-5 and 2-3 folds, respectively with increase in metal concentration from 25-100 ppm and incubation period from 48, 72 and 96 hours over control. Present study concludes that A. alternata was able to tolerate up to 90 ppm of copper, therefore it is imperative to consider fungus metal tolerance range during fungicide formulations. </div>

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Circular DNA Plasmid in the Phytopathogenic Fungus Alternaria alternata: Its Temperature-Dependent Curing and Association with Pathogenicity

Genetics ◽

10.1093/genetics/146.1.111 ◽

1997 ◽

Vol 146 (1) ◽

pp. 111-120

Author(s):

Satoshi Katsuya ◽

Isao Kaneko ◽

Makiko Owaki ◽

Kouichi Ishikawa ◽

Takashi Tsujimoto ◽

...

Keyword(s):

Blot Analysis ◽

Alternaria Alternata ◽

Black Spot ◽

Electron Microscopic Observation ◽

Toxin Production ◽

Japanese Pear ◽

Phytopathogenic Fungus ◽

Temperature Dependent ◽

Electron Microscopic ◽

Endonuclease Mapping

We found the presence of plasmid DNA in strain T88-56 of the Japanese pear pathotype of Alternaria alternata, which causes black spot of certain cultivars of Japanese pear by producing host-specific AK-toxin. The plasmid, designated pAAT56, was identified to be an ∼5.4-kilobase (kb) circular molecule by electron microscopic observation and restriction endonuclease mapping. Southern blot analysis showed that pAAT56 DNA had no homology with either nuclear or mitochondrial DNA. Cultures of strain T88-56 grown at 26° showed markedly reduced plasmid levels relative to those grown at lower temperatures. The strain was completely cured of pAAT56 during growth at 29°. Temperature-dependent curing of pAAT56 was confirmed by using single-protoplast isolates from mycelia grown at 23°, most of which maintained the plasmid, and from mycelia grown at 29°, most of which had lost the plasmid. Northern blot analysis detected the presence of three RNA species (∼1.7, 2.7 and 5.4 kb) transcribed from pAAT56. The biological function of pAAT56 was observed using single-protoplast isolates from mycelia that either contained or had been cured of pAAT56. The plasmid-containing isolates tended to be reduced in AK-toxin production and pathogenicity compared with the plasmid-cured isolates.

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