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Oxidative stress response of Mycosphaerella fijiensis, the causal agent of black leaf streak disease in banana plants, to hydrogen peroxide and paraquat

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Mycosphaerella fijiensis causes black leaf streak disease in banana and plantain. This fungus is usually attacked by reactive oxygen species secreted by the plant or during exposure to fungicide, however, little is known about the antioxidant response of the fungus. In this study, mycelia were observed to totally decompose 30 mmol/L of hydrogen peroxide (H2O2) within 120 min, liberating oxygen bubbles, and also to survive in concentrations as high as 100 mmol/L H2O2. The oxidative stress responses to H2O2, paraquat, and hydroquinone were characterized in terms of the activities of catalase and superoxide dismutase (SOD). Two active catalase bands were seen in native PAGE induced by H2O2. Band I had monofunctional activity and band II had bifunctional catalase-peroxidase activity. Two isozymes of SOD, distinguishable by their cyanide sensitivity, were found; CuZnSOD was the main one. The combination of H2O2 and 3-aminotriazole reduced the accumulation of biomass up to 40% compared with exposure to H2O2 alone, suggesting that catalase is important for the rapid decomposition of H2O2 and has a direct bearing on cell viability. The results also suggest that the superoxide anion formed through the redox of paraquat and hydroquinone has a greater effect than H2O2 on the cellular viability of M. fijiensis.

Mycosphaerella fijiensis est l’agent responsable de la maladie de la raie noire de la banane et du plantain. Ce champignon est habituellement attaqué par les espèces réactives d’oxygène secrétées par la plante ou pendant une exposition aux fongicides; cependant, on connaît peu de choses de la réponse antioxydante du champignon. Dans cette étude, les mycéliums ont décomposé totalement 30 mmol/L de H2O2 en moins de 120 min, libérant des bulles d’oxygène, et ils étaient capables de survivre à des concentrations aussi élevées que 100 mmol/L de H2O2. La réponse au stress oxydatif produit par le H2O2, le paraquat et l’hydroquinone a été caractérisée en termes d’activité de la catalase et de la superoxyde dismutase (SOD). Deux bandes de catalase active induites par le H2O2 été observées en PAGE natif. La bande I possédait une activité monofonctionnelle et la bande II possédait une activité bifonctionnelle catalase-peroxydase. Deux isozymes de la SOD, caractérisées par leur sensibilité au cyanure, ont été trouvées, la CuZnSOD étant la principale. La combinaison de H2O2 et de 3-aminotriazole réduit l’accumulation de biomasse jusqu’à 40 % comparativement au H2O2 seul, suggérant que la catalase est importante pour la décomposition rapide du H2O2 et qu’elle a un lien direct avec la viabilité cellulaire. Les résultats suggèrent aussi que l’anion superoxyde formé par l’oxydoréduction du paraquat et de l’hydroquinone a un effet plus fort que le H2O2 sur la viabilité cellulaire de M. fijiensis.

Document Type: Research Article

Publication date: 2009-07-01

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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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