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Research Support, Non-U.S. Gov'ts
- Involvement of Alternative Oxidase in the Regulation of Sensitivity of Sclerotinia sclerotiorum to the Fungicides Azoxystrobin and Procymidone
- Ting Xu , Ya-Ting Wang , Wu-Sheng Liang , Fei Yao , Yong-Hong Li , Dian-Rong Li , Hao Wang , Zheng-Yi Wang
- J. Microbiol. 2013;51(3):352-358. Published online April 26, 2013
- DOI: https://doi.org/10.1007/s12275-013-2534-x
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- 29 Scopus
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Abstract
- Sclerotinia sclerotiorum is a filamentous fungal pathogen that can infect many economically important crops and vegetables. Alternative oxidase is the terminal oxidase of the alternative respiratory pathway in fungal mitochondria. The function of alternative oxidase was investigated in the regulation of sensitivity of S. sclerotiorum to two commercial fungicides, azoxystrobin and procymidone which have different fungitoxic mechanisms. Two isolates of S. sclerotiorum were sensitive to both fungicides. Application of salicylhydroxamic acid, a specific inhibitor of alternative oxidase, significantly increased the values of effective concentration causing 50% mycelial growth inhibition (EC50) of azoxystrobin to both S. sclerotiorum isolates, whereas notably decreased the EC50 values of procymidone. In mycelial respiration assay azoxystrobin displayed immediate inhibitory effect on cytochrome pathway capacity, but had no immediate effect on alternative pathway capacity. In contrast, procymidone showed no immediate impact on capacities of both cytochrome and alternative pathways in the mycelia. However, alternative oxidase encoding gene (aox) transcript and protein levels, alternative respiration pathway capacity of the mycelia were obviously increased by pre-treatment for 24 h with both azoxystrobin and procymidone. These results indicate that alternative oxidase was involved in the regulation of sensitivity of S. sclerotiorum to the fungicides azoxystrobin and procymidone, and that both fungicides could affect aox gene expression and the alternative respiration pathway capacity development in mycelia of this fungal pathogen.
- Selection of a Streptomyces Strain Able to Produce Cell Wall Degrading Enzymes and Active against Sclerotinia sclerotiorum
- Adriana Fróes , Andrew Macrae , Juliana Rosa , Marcella Franco , Rodrigo Souza , Rosângela Soares , Rosalie Coelho
- J. Microbiol. 2012;50(5):798-806. Published online November 4, 2012
- DOI: https://doi.org/10.1007/s12275-012-2060-2
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- 19 Scopus
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Abstract
- Control of plant pathogen Sclerotinia sclerotiorum is an ongoing challenge because of its wide host range and the persistence of its sclerotia in soil. Fungicides are the most commonly used method to control this fungus but these can have ecotoxicity impacts. Chitinolytic Streptomyces strains isolated from Brazilian tropical soils were capable of inhibiting S. sclerotiorum growth in vitro, offering new possibilities for integrated pest management and biocontrol, with a new approach to dealing with an old problem. Strain Streptomyces sp. 80 was capable of irreversibly inhibiting fungal growth. Compared to other strains, its crude enzymes had the highest chitinolytic levels when measured at 25°C and strongly inhibited sclerotia from S. sclerotiorum. It produced four hydrolytic enzymes involved in fungal cell wall degradation when cultured in presence of the fungal mycelium. The best production, obtained after three days, was 0.75 U/ml for exochitinase, 0.9 U/ml for endochitinase, 0.16 U/ml for glucanase, and 1.78 U/ml for peptidase. Zymogram analysis confirmed two hydrolytic bands of chitinolytic activity with apparent molecular masses of 45.8 and 206.8 kDa. One glucanase activity with an apparent molecular mass of 55 kDa was also recorded, as well as seven bands of peptidase activity with apparent molecular masses ranging from 15.5 to 108.4 kDa. Differential interference contrast microscopy also showed alterations of hyphal morphology after co-culture. Streptomyces sp. 80 seems to be promising as a biocontrol agent against S. sclerotiorum, contributing to the development of new methods for controlling plant diseases and reducing the negative impact of using fungicides.
- Involvement of Alternative Oxidase in the Regulation of Growth, Development, and Resistance to Oxidative Stress of Sclerotinia sclerotiorum
- Ting Xu , Fei Yao , Wu-Sheng Liang , Yong-Hong Li , Dian-Rong Li , Hao Wang , Zheng-Yi Wang
- J. Microbiol. 2012;50(4):594-602. Published online August 25, 2012
- DOI: https://doi.org/10.1007/s12275-012-2015-7
- 48 View
- 0 Download
- 37 Scopus
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Abstract
- Sclerotinia sclerotiorum is a cosmopolitan, filamentous, fungal pathogen that can cause serious disease in many kinds of crops. Alternative oxidase is the terminal oxidase of the alternative mitochondrial respiratory pathway in fungi and higher plants. We report the presence of this alternative pathway respiration and demonstrate its expression in two isolates of S. sclerotiorum under unstressed, normal culture conditions. Application of salicylhydroxamic acid, a specific inhibitor of alternative oxidase, severely inhibited the mycelial growth of S. sclerotiorum both on potato dextrose agar plates and in liquid culture media. Inhibition of alternative oxidase could influence the growth pattern of S. sclerotiorum, as salicylhydroxamic acid treatment induced obvious aerial mycelia growing on potato dextrose agar plates. Under the treatment with salicylhydroxamic acid, S. sclerotiorum formed sclerotia much more slowly than the control. Treatment with hydrogen peroxide in millimolar concentrations greatly decreased the growth rate of mycelia and delayed the formation of sclerotia in both tested S. sclerotiorum isolates. As well, this treatment obviously increased their alternative pathway respiration and the levels of both mRNA and protein of the alternative oxidase. These results indicate that alternative oxidase is involved in the regulation of growth, development, and resistance to oxidative stress of S. sclerotiorum.
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