Inhibition of Aflatoxin Production by Paraquat and External Superoxide Dismutase in <i>Aspergillus flavus</i>
Aflatoxin contamination of crops is a worldwide problem, and elucidation of the regulatory mechanism of aflatoxin production, for example relative to the oxidative⁻antioxidative system, is needed. Studies have shown that oxidative stress induced by reactive oxygen species promotes aflatoxi...
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doaj-c3c6e44fae664db38dda2c1fe1ed6cd72020-11-24T21:16:00ZengMDPI AGToxins2072-66512019-02-0111210710.3390/toxins11020107toxins11020107Inhibition of Aflatoxin Production by Paraquat and External Superoxide Dismutase in <i>Aspergillus flavus</i>Tomohiro Furukawa0Shohei Sakuda1Department of Biosciences, Teikyo University, 1-1 Toyosatodai, Utsunomiya 320-8551, JapanDepartment of Biosciences, Teikyo University, 1-1 Toyosatodai, Utsunomiya 320-8551, JapanAflatoxin contamination of crops is a worldwide problem, and elucidation of the regulatory mechanism of aflatoxin production, for example relative to the oxidative⁻antioxidative system, is needed. Studies have shown that oxidative stress induced by reactive oxygen species promotes aflatoxin production. However, superoxide has been suggested to have the opposite effect. Here, we investigated the effects of the superoxide generator, paraquat, and externally added superoxide dismutase (SOD) on aflatoxin production in <i>Aspergillus flavus</i>. Paraquat with an IC<sub>50</sub> value of 54.9 µM inhibited aflatoxin production without affecting fungal growth. It increased cytosolic and mitochondrial superoxide levels and downregulated the transcription of aflatoxin biosynthetic cluster genes, including <i>aflR</i>, a key regulatory protein. The addition of bovine Cu/ZnSOD to the culture medium suppressed the paraquat-induced increase in superoxide levels, but it did not fully restore paraquat-inhibited aflatoxin production because bovine Cu/ZnSOD with an IC<sub>50</sub> value of 17.9 µg/mL itself inhibited aflatoxin production. Externally added bovine Cu/ZnSOD increased the SOD activity in fungal cell extracts and upregulated the transcription of genes encoding Cu/ZnSOD and alcohol dehydrogenase. These results suggest that intracellular accumulation of superoxide impairs aflatoxin production by downregulating <i>aflR</i> expression, and that externally added Cu/ZnSOD also suppresses aflatoxin production by a mechanism other than canonical superoxide elimination activity.https://www.mdpi.com/2072-6651/11/2/107aflatoxin production<i>Aspergillus flavus</i>superoxideparaquatsuperoxide dismutase |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Tomohiro Furukawa Shohei Sakuda |
spellingShingle |
Tomohiro Furukawa Shohei Sakuda Inhibition of Aflatoxin Production by Paraquat and External Superoxide Dismutase in <i>Aspergillus flavus</i> Toxins aflatoxin production <i>Aspergillus flavus</i> superoxide paraquat superoxide dismutase |
author_facet |
Tomohiro Furukawa Shohei Sakuda |
author_sort |
Tomohiro Furukawa |
title |
Inhibition of Aflatoxin Production by Paraquat and External Superoxide Dismutase in <i>Aspergillus flavus</i> |
title_short |
Inhibition of Aflatoxin Production by Paraquat and External Superoxide Dismutase in <i>Aspergillus flavus</i> |
title_full |
Inhibition of Aflatoxin Production by Paraquat and External Superoxide Dismutase in <i>Aspergillus flavus</i> |
title_fullStr |
Inhibition of Aflatoxin Production by Paraquat and External Superoxide Dismutase in <i>Aspergillus flavus</i> |
title_full_unstemmed |
Inhibition of Aflatoxin Production by Paraquat and External Superoxide Dismutase in <i>Aspergillus flavus</i> |
title_sort |
inhibition of aflatoxin production by paraquat and external superoxide dismutase in <i>aspergillus flavus</i> |
publisher |
MDPI AG |
series |
Toxins |
issn |
2072-6651 |
publishDate |
2019-02-01 |
description |
Aflatoxin contamination of crops is a worldwide problem, and elucidation of the regulatory mechanism of aflatoxin production, for example relative to the oxidative⁻antioxidative system, is needed. Studies have shown that oxidative stress induced by reactive oxygen species promotes aflatoxin production. However, superoxide has been suggested to have the opposite effect. Here, we investigated the effects of the superoxide generator, paraquat, and externally added superoxide dismutase (SOD) on aflatoxin production in <i>Aspergillus flavus</i>. Paraquat with an IC<sub>50</sub> value of 54.9 µM inhibited aflatoxin production without affecting fungal growth. It increased cytosolic and mitochondrial superoxide levels and downregulated the transcription of aflatoxin biosynthetic cluster genes, including <i>aflR</i>, a key regulatory protein. The addition of bovine Cu/ZnSOD to the culture medium suppressed the paraquat-induced increase in superoxide levels, but it did not fully restore paraquat-inhibited aflatoxin production because bovine Cu/ZnSOD with an IC<sub>50</sub> value of 17.9 µg/mL itself inhibited aflatoxin production. Externally added bovine Cu/ZnSOD increased the SOD activity in fungal cell extracts and upregulated the transcription of genes encoding Cu/ZnSOD and alcohol dehydrogenase. These results suggest that intracellular accumulation of superoxide impairs aflatoxin production by downregulating <i>aflR</i> expression, and that externally added Cu/ZnSOD also suppresses aflatoxin production by a mechanism other than canonical superoxide elimination activity. |
topic |
aflatoxin production <i>Aspergillus flavus</i> superoxide paraquat superoxide dismutase |
url |
https://www.mdpi.com/2072-6651/11/2/107 |
work_keys_str_mv |
AT tomohirofurukawa inhibitionofaflatoxinproductionbyparaquatandexternalsuperoxidedismutaseiniaspergillusflavusi AT shoheisakuda inhibitionofaflatoxinproductionbyparaquatandexternalsuperoxidedismutaseiniaspergillusflavusi |
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