Marilyn Ehrenshaft

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■ Abstract Plant pathogenic fungi in eight genera produce light-activated perylenequinone toxins that are toxic to plants via the generation of activated oxygen species, particularly singlet oxygen. Studies on the cercosporin toxin produced by Cercospora species have documented an important role for this toxin in pathogenesis of host plants.(More)
Many species of the fungal genus Cercospora, including the soybean pathogen C. kikuchii, produce the phytotoxic polyketide cercosporin. Cercosporin production is induced by light. Previously, we identified several cDNA clones of mRNA transcripts that exhibited light-enhanced accumulation in C. kikuchii. Targeted disruption of the genomic copy of one of(More)
Reactive oxygen species (ROS) are both signal molecules and direct participants in plant defense against pathogens. Many fungi synthesize mannitol, a potent quencher of ROS, and there is growing evidence that at least some phytopathogenic fungi use mannitol to suppress ROS-mediated plant defenses. Here we show induction of mannitol production and secretion(More)
The Cercospora nicotianae SOR1 (singlet oxygen resistance) gene was identified previously as a gene involved in resistance of this fungus to singlet-oxygen-generating phototoxins. Although homologues to SOR1 occur in organisms in four kingdoms and encode one of the most highly conserved proteins yet identified, the precise function of this protein has,(More)
Cercosporin, a photosensitizing perylenequinone toxin produced by the plant pathogenic Cercospora fungi, generates the highly toxic singlet oxygen (1O2) upon exposure to light. Cercosporin shows broad toxicity against a wide range of organisms, including bacteria, fungi, plants, and animals; however, Cercospora fungi are resistant to its effects. A novel(More)
Vitamin B6 (pyridoxine, 1) and its derivatives: pyridoxal (2), pyridoxal 5-phosphate (3) and pyridoxamine (4) are important natural compounds involved in numerous biological functions. Pyridoxine appears to play a role in the resistance of the filamentous fungus Cercospora nicotianae to its own abundantly produced strong photosensitizer of singlet molecular(More)
Function of the cyanide-sensitive mitochondrial electron transport system was required for germination of the Zea mays embryo. Respiration of the standard electron transport system (rather than the alternate oxidase) began immediately upon initiation of imbibition. This respiration depended upon cytochrome c oxidase and ATPase that were conserved in an(More)
Filamentous Cercospora fungi are resistant to photosensitizing compounds that generate singlet oxygen. C. nicotianae photosensitizer-sensitive mutants were restored to full resistance by transformation with SOR1 (Singlet Oxygen Resistance 1), a gene recovered from a wild-type genomic library. SOR1 null mutants generated via targeted gene replacement(More)
We have successfully adapted plasmid insertion and restriction enzyme-mediated integration (REMI) to produce cercosporin toxin-deficient mutants in the asexual phytopathogenic fungus Cercospora nicotianae. The use of pre-linearized plasmid or restriction enzymes in the transformation procedure significantly decreased the transformation frequency, but(More)
Nano-sized titanium dioxide (TiO(2)) is among the top five widely used nanomaterials for various applications. In this study, we determine the phototoxicity of TiO(2) nanoparticles (nano-TiO(2)) with different molecular sizes and crystal forms (anatase and rutile) in human skin keratinocytes under UVA irradiation. Our results show that all nano-TiO(2)(More)