Alternative oxidase respiration in the mycorrhizal fungus Laccaria bicolor
The temperature on Earth is rising, and one of the main drivers is anthropogen-ic greenhouse gases such as carbon dioxide (CO2). The world’s forests act as carbon sinks, binding carbon into their biomass. The net carbon assimilation is determined by the uptake and release of CO2 through the processe...
| Autor principal: | |
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| Formato: | H2 |
| Lenguaje: | Inglés sueco |
| Publicado: |
SLU/Dept. of Forest Ecology and Management
2019
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| Materias: |
| _version_ | 1855572530514886656 |
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| author | Mikaelsson, Hilda |
| author_browse | Mikaelsson, Hilda |
| author_facet | Mikaelsson, Hilda |
| author_sort | Mikaelsson, Hilda |
| collection | Epsilon Archive for Student Projects |
| description | The temperature on Earth is rising, and one of the main drivers is anthropogen-ic greenhouse gases such as carbon dioxide (CO2). The world’s forests act as carbon sinks, binding carbon into their biomass. The net carbon assimilation is determined by the uptake and release of CO2 through the processes of photo-synthesis and respiration. Respiration in plants and most fungi can proceed via two pathways. The most frequently used pathway ends with the terminal com-plex Cytochrome C oxidase (COX), but it can also follow a less efficient alter-native pathway, which ends with Alternative oxidase (AOX). The rate by which plants and other organisms use the alternative pathway affects their carbon use efficiency.
Both enzymes use atmospheric oxygen as their substrate, but they discrimi-nate differently against the isotope 18O. In this study, the presence of AOX in the mycorrhizal fungus Laccaria bicolor was proven, using isotope ratio mass spectrometry (IRMS). Based on the 18O discrimination of the mycelium in the presence of pathway specific inhibitors, the electron partitioning to each path-way in untreated mycelium (i.e. without inhibitors) was estimated.
As found in previous studies on plants, the discrimination was found to be affected by the water content of the sample. Since this effect was probably derived from diffusion limitation, all discrimination values were normalized to correspond to the mean water content, 94.4%. The 18O discrimination of L. bicolor was found to be 18.8±0.9, which is comparable to COX values previ-ously found in plants and to discrimination values of baker’s yeast, Saccar-omyces cerevisiae, which lacks AOX. This indicated that the use of AOX in young mycelium of L. bicolor was negligible. However, a correlation was dis-covered between AOX contribution and age, suggesting that AOX plays an increasingly important role in ageing mycelium.
The oxygen isotope discrimination method is currently the only reliable way of measuring AOX/COX partitioning during respiration. However, despite numerous studies in various species, this is the first time it has been applied to fungal mycelium, and as such it represents an important step towards a greater understanding of fungal respiration. Further studies of fungal AOX under natu-ral conditions, in combination with estimations of fungal biomass, has a great potential to improve the accuracy of carbon sequestration models. |
| format | H2 |
| id | RepoSLU15145 |
| institution | Swedish University of Agricultural Sciences |
| language | Inglés swe |
| publishDate | 2019 |
| publishDateSort | 2019 |
| publisher | SLU/Dept. of Forest Ecology and Management |
| publisherStr | SLU/Dept. of Forest Ecology and Management |
| record_format | eprints |
| spelling | RepoSLU151452019-10-16T01:02:09Z Alternative oxidase respiration in the mycorrhizal fungus Laccaria bicolor Respiration via alternativt oxidas i mykorrhizasvampen Laccaria bicolor Mikaelsson, Hilda L. bicolor mycel ektomykorrhiza cellandning AOX alternativt oxidas cytokromoxidas cyanid mycelium ectomychorriza respiration alternative oxidase cytochrome oxidase salicylhydroxamic acid n-propyl gallate cyanide The temperature on Earth is rising, and one of the main drivers is anthropogen-ic greenhouse gases such as carbon dioxide (CO2). The world’s forests act as carbon sinks, binding carbon into their biomass. The net carbon assimilation is determined by the uptake and release of CO2 through the processes of photo-synthesis and respiration. Respiration in plants and most fungi can proceed via two pathways. The most frequently used pathway ends with the terminal com-plex Cytochrome C oxidase (COX), but it can also follow a less efficient alter-native pathway, which ends with Alternative oxidase (AOX). The rate by which plants and other organisms use the alternative pathway affects their carbon use efficiency. Both enzymes use atmospheric oxygen as their substrate, but they discrimi-nate differently against the isotope 18O. In this study, the presence of AOX in the mycorrhizal fungus Laccaria bicolor was proven, using isotope ratio mass spectrometry (IRMS). Based on the 18O discrimination of the mycelium in the presence of pathway specific inhibitors, the electron partitioning to each path-way in untreated mycelium (i.e. without inhibitors) was estimated. As found in previous studies on plants, the discrimination was found to be affected by the water content of the sample. Since this effect was probably derived from diffusion limitation, all discrimination values were normalized to correspond to the mean water content, 94.4%. The 18O discrimination of L. bicolor was found to be 18.8±0.9, which is comparable to COX values previ-ously found in plants and to discrimination values of baker’s yeast, Saccar-omyces cerevisiae, which lacks AOX. This indicated that the use of AOX in young mycelium of L. bicolor was negligible. However, a correlation was dis-covered between AOX contribution and age, suggesting that AOX plays an increasingly important role in ageing mycelium. The oxygen isotope discrimination method is currently the only reliable way of measuring AOX/COX partitioning during respiration. However, despite numerous studies in various species, this is the first time it has been applied to fungal mycelium, and as such it represents an important step towards a greater understanding of fungal respiration. Further studies of fungal AOX under natu-ral conditions, in combination with estimations of fungal biomass, has a great potential to improve the accuracy of carbon sequestration models. Temperaturen på Jorden stiger, och en av de främsta orsakerna är antropogena växthusgaser som koldioxid (CO2). Världens skogar fungerar som kolsänkor, då de binder in kol i sin biomassa. Den totala mängd kol som lagras in bestäms av upptag och avgång av CO2 under fotosyntes och respiration. Respiration i växter och de flesta svampar kan ske via två olika vägar. Den mest använda avslutas med enzymet cytokrom C (COX), medan den alternativa och mindre effektiva vägen slutar med enzymet alternativt oxidas (AOX). Användandet av AOX påverkar hur effektivt organismen använder kolet den tar upp. Båda enzymerna använder sig av syre från atmosfären som substrat, men de diskriminerar olika starkt mot syreisotopen 18O. I den här studien visas att en-zymet AOX finns i mykorrizasvampen Laccaria bicolor, och dess användning mäts med hjälp av masspektrometri av isotopiska förhållanden (IRMS). Dis-krimineringen av syreisotopen 18O uppskattades för varje enzym med hjälp av inhibitorer och användes sedan för att räkna ut elektrondelningen mellan de olika respirationsvägarna i obehandlat mycel, d.v.s. utan tillsatta inhibitorer. Liksom i tidigare studier visade sig diskrimineringen vara påverkad av pro-vets vatteninnehåll. Eftersom denna effekt troligtvis uppkommit på grund av diffusionsbegränsning av substratet normaliserades alla diskrimineringsvärden till det som motsvarade det genomsnittliga vatteninnehållet, 94,4%. Diskrimi-neringen av 18O i L. bicolor var 18,8±0,9, vilket är jämförbart med de värden som presenterats för växter och jästsvampen Saccaromyces cerevisiae, vilken saknar AOX. Detta indikerade att användandet av AOX är försumbart i ungt mycel. Dock kunde ett samband påvisas mellan AOX-användning och ålder, vilket antyder att AOX spelar en allt viktigare roll allt eftersom mycelet åldras. IRMS är den enda tillförlitliga metoden för mätning av elektronfördelning mellan AOX och COX. Ändå, trots otaliga studier i olika arter, är detta första gången som denna metod används i svampmycel. Arbetet som sådant utgör därför ett viktigt steg mot en större förståelse av svampars respiration. Vidare studier av AOX i svamp under naturliga förhållanden, i kombination med uppskattningar av svampars biomassa, har stor potential att ytterligare förbättra säkerheten i kolinlagringsmodeller. SLU/Dept. of Forest Ecology and Management 2019 H2 eng swe https://stud.epsilon.slu.se/15145/ |
| spellingShingle | L. bicolor mycel ektomykorrhiza cellandning AOX alternativt oxidas cytokromoxidas cyanid mycelium ectomychorriza respiration alternative oxidase cytochrome oxidase salicylhydroxamic acid n-propyl gallate cyanide Mikaelsson, Hilda Alternative oxidase respiration in the mycorrhizal fungus Laccaria bicolor |
| title | Alternative oxidase respiration in the mycorrhizal fungus Laccaria bicolor |
| title_full | Alternative oxidase respiration in the mycorrhizal fungus Laccaria bicolor |
| title_fullStr | Alternative oxidase respiration in the mycorrhizal fungus Laccaria bicolor |
| title_full_unstemmed | Alternative oxidase respiration in the mycorrhizal fungus Laccaria bicolor |
| title_short | Alternative oxidase respiration in the mycorrhizal fungus Laccaria bicolor |
| title_sort | alternative oxidase respiration in the mycorrhizal fungus laccaria bicolor |
| topic | L. bicolor mycel ektomykorrhiza cellandning AOX alternativt oxidas cytokromoxidas cyanid mycelium ectomychorriza respiration alternative oxidase cytochrome oxidase salicylhydroxamic acid n-propyl gallate cyanide |