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Enzyme activities associated with oxidative stress in Metarhizium anisopliae during germination, mycelial growth, and conidiation and in response to near-UV irradiation

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Abstract:

Metarhizium anisopliae isolates have a wide insect host range, but an impediment to their commercial use as a biocontrol agent of above-ground insects is the high susceptibility of spores to the near-UV present in solar irradiation. To understand stress responses in M. anisopliae, we initiated studies of enzymes that protect against oxidative stress in two strains selected because their spores differed in sensitivity to UV-B. Spores of the more near-UV resistant strain in M. anisopliae 324 displayed different isozyme profiles for catalase–peroxidase, glutathione reductase, and superoxide dismutase when compared with the less resistant strain 2575. A transient loss in activity of catalase–peroxidase and glutathione reductase was observed during germination of the spores, whereas the intensity of isozymes displaying superoxide dismutase did not change as the mycelium developed. Isozyme composition for catalase–peroxidases and glutathione reductase in germlings changed with growth phase. UV-B exposure from lamps reduced the activity of isozymes displaying catalase–peroxidase and glutathione reductase activities in 2575 more than in 324. The major effect of solar UV-A plus UV-B also was a reduction in catalase–peroxidases isozyme level, a finding confirmed by measurement of catalase specific activity. Impaired growth of M. anisopliae after near-UV exposure may be related to reduced abilities to handle oxidative stress.Key words: catalase–peroxidase, germination, glutathione reductase, Metarhizium anisopliae, near-UV, protein oxidation, superoxide dismutase.

Les isolats de Metarhizium anisopliae ont un large spectre d'insectes-hôtes, mais un obstacle à leur utilisation commerciale comme agents de biocontrôle d'insectes de surface est la susceptibilité élevée des spores aux proches UV présents dans les radiations solaires. Afin de comprendre les réponses au stress chez M. anisopliae, nous avons entrepris d'étudier les enzymes qui protègent contre le stress oxydatif chez deux souches sélectionnées pour leur spores dont la sensibilité aux UV-B différait. Les spores de la souche 324 qui était plus résistante aux proches UV a démontré des profils différents d'isozymes pour la catalase–peroxydase, la glutathion réductase et la superoxyde dismutase comparativement à la souche 2575 moins résistante. Une perte transitoire de l'activité de la catalase–peroxydase et de la glutathion réductase a été observée lors de la germination des spores, alors que l'intensité des isozymes ayant une activité superoxyde dismutase n'a pas changé au fur et à mesure que le mycélium se développait. La composition des isozymes en catalase–peroxydases et en glutathion réductase chez les spores en germination a changé selon la phase de croissance. Une exposition à des UV-B à partir de lampes a davantage diminué l'activité d'isozymes démontrant des activités catalase–peroxydase et glutathion réductase chez 2575 que chez 324. L'impact majeur des UV-A plus UV-B fut également une diminution des niveaux d'isozymes catalase–peroxydase, une découverte confirmée par la mesure de l'activité spécifique à la catalase. La croissance plus faible de M. anisopliae après une exposition aux proches UV pourrait être reliée a une capacité réduite de faire face au stress oxydatif.Mots clés : catalase–peroxydase, germination, glutathion réductase, Metarhizium anisopliae, proche UV, oxydation des protéines, superoxyde dismutase.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: January 1, 2004

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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