Effect of azoxystrobin on activities of antioxidant enzymes and alternative oxidase in wheat head blight pathogens Fusarium graminearum and Microdochium nivale
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Wheat head blight pathogens Fusarium graminearum and Microdochium nivale have distinct sensitivities to strobilurin fungicides, which inhibit activity of complex III in the mitochondrial electron transport chain. When mycelia were cultured in medium with the strobilurin fungicide azoxystrobin (AZ), F. graminearum increased its oxygen-consumption, but M. nivale, which is more sensitive than Fusarium species to strobilurins, did not. There was no increase in oxygen consumption in F. graminearum by the treatment with AZ and alternative oxidase (AOX) inhibitor n-propyl gallate. AZ enhanced the generation of intracellular H2O2 in both fungi. Activities of antioxidant enzymes in M. nivale were consistently higher than in F. graminearum. Quantification of AOX transcripts by real-time PCR indicated that transcription of AOX in F. graminearum and M. nivale was induced by AZ, suggesting that AOX activities in both fungi are regulated at the transcriptional level. AOX transcription in F. graminearum was rapidly induced by AZ and reached a maximum by 60 min after treatment. On the contrary, induction in M. nivale was low and slow. These results suggest that differential ability of F. graminearum and M. nivale to activate AOX transcription is involved in the difference in their sensitivity to AZ.
KeywordsAzoxystrobin Antioxidant enzymes Alternative oxidase Fusarium head blight Fusarium graminearum Microdochium nivale
We thank Dr. Hatsuo Saitoh, National Agricultural Research Center and Dr. Takashi Nakajima, National Agricultural Research Center for Kyushu Okinawa Region and Microorganisms Section of the MAFF Genebank in National Institute of Agrobiological Sciences for providing fungal strains; and Syngenta Japan and BASF Agro for providing AZ and KM, respectively. We extend special thanks to Dr. Tsung-Chun Lin, Graduate School of Life and Environmental Sciences, University of Tsukuba, for statistical analyses. This research was supported by a grant for Integrated Research Program for Functionality and Safety of Food Toward an Establishment of Healthy Diet from Ministry of Agriculture, Forestry & Fisheries.
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