Examining the Effects of the Nitrogen Environment on Growth and N(2)-Fixation of Endophytic Herbaspirillum seropedicae in Maize Seedlings by Applying (11)C Radiotracing
Herbaspirillum seropedicae, as an endophyte and prolific root colonizer of numerous cereal crops, occupies an important ecological niche in agriculture because of its ability to promote plant growth and potentially improve crop yield. More importantly, there exists the untapped potential to harness...
Autores principales: | , , , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
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MDPI
2021
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8401641/ https://www.ncbi.nlm.nih.gov/pubmed/34442661 http://dx.doi.org/10.3390/microorganisms9081582 |
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author | Waller, Spenser Wilder, Stacy L. Schueller, Michael J. Housh, Alexandra B. Scott, Stephanie Benoit, Mary Powell, Avery Powell, Garren Ferrieri, Richard A. |
author_facet | Waller, Spenser Wilder, Stacy L. Schueller, Michael J. Housh, Alexandra B. Scott, Stephanie Benoit, Mary Powell, Avery Powell, Garren Ferrieri, Richard A. |
author_sort | Waller, Spenser |
collection | PubMed |
description | Herbaspirillum seropedicae, as an endophyte and prolific root colonizer of numerous cereal crops, occupies an important ecological niche in agriculture because of its ability to promote plant growth and potentially improve crop yield. More importantly, there exists the untapped potential to harness its ability, as a diazotroph, to fix atmospheric N(2) as an alternative nitrogen resource to synthetic fertilizers. While mechanisms for plant growth promotion remain controversial, especially in cereal crops, one irrefutable fact is these microorganisms rely heavily on plant-borne carbon as their main energy source in support of their own growth and biological functions. Biological nitrogen fixation (BNF), a microbial function that is reliant on nitrogenase enzyme activity, is extremely sensitive to the localized nitrogen environment of the microorganism. However, whether internal root colonization can serve to shield the microorganisms and de-sensitize nitrogenase activity to changes in the soil nitrogen status remains unanswered. We used RAM10, a GFP-reporting strain of H. seropedicae, and administered radioactive (11)CO(2) tracer to intact 3-week-old maize leaves and followed (11)C-photosynthates to sites within intact roots where actively fluorescing microbial colonies assimilated the tracer. We examined the influence of administering either 1 mM or 10 mM nitrate during plant growth on microbial demands for plant-borne (11)C. Nitrogenase activity was also examined under the same growth conditions using the acetylene reduction assay. We found that plant growth under low nitrate resulted in higher nitrogenase activity as well as higher microbial demands for plant-borne carbon than plant growth under high nitrate. However, carbon availability was significantly diminished under low nitrate growth due to reduced host CO(2) fixation and reduced allocation of carbon resources to the roots. This response of the host caused significant inhibition of microbial growth. In summary, internal root colonization did little to shield these endophytic microorganisms from the nitrogen environment. |
format | Online Article Text |
id | pubmed-8401641 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2021 |
publisher | MDPI |
record_format | MEDLINE/PubMed |
spelling | pubmed-84016412021-08-29 Examining the Effects of the Nitrogen Environment on Growth and N(2)-Fixation of Endophytic Herbaspirillum seropedicae in Maize Seedlings by Applying (11)C Radiotracing Waller, Spenser Wilder, Stacy L. Schueller, Michael J. Housh, Alexandra B. Scott, Stephanie Benoit, Mary Powell, Avery Powell, Garren Ferrieri, Richard A. Microorganisms Article Herbaspirillum seropedicae, as an endophyte and prolific root colonizer of numerous cereal crops, occupies an important ecological niche in agriculture because of its ability to promote plant growth and potentially improve crop yield. More importantly, there exists the untapped potential to harness its ability, as a diazotroph, to fix atmospheric N(2) as an alternative nitrogen resource to synthetic fertilizers. While mechanisms for plant growth promotion remain controversial, especially in cereal crops, one irrefutable fact is these microorganisms rely heavily on plant-borne carbon as their main energy source in support of their own growth and biological functions. Biological nitrogen fixation (BNF), a microbial function that is reliant on nitrogenase enzyme activity, is extremely sensitive to the localized nitrogen environment of the microorganism. However, whether internal root colonization can serve to shield the microorganisms and de-sensitize nitrogenase activity to changes in the soil nitrogen status remains unanswered. We used RAM10, a GFP-reporting strain of H. seropedicae, and administered radioactive (11)CO(2) tracer to intact 3-week-old maize leaves and followed (11)C-photosynthates to sites within intact roots where actively fluorescing microbial colonies assimilated the tracer. We examined the influence of administering either 1 mM or 10 mM nitrate during plant growth on microbial demands for plant-borne (11)C. Nitrogenase activity was also examined under the same growth conditions using the acetylene reduction assay. We found that plant growth under low nitrate resulted in higher nitrogenase activity as well as higher microbial demands for plant-borne carbon than plant growth under high nitrate. However, carbon availability was significantly diminished under low nitrate growth due to reduced host CO(2) fixation and reduced allocation of carbon resources to the roots. This response of the host caused significant inhibition of microbial growth. In summary, internal root colonization did little to shield these endophytic microorganisms from the nitrogen environment. MDPI 2021-07-25 /pmc/articles/PMC8401641/ /pubmed/34442661 http://dx.doi.org/10.3390/microorganisms9081582 Text en © 2021 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). |
spellingShingle | Article Waller, Spenser Wilder, Stacy L. Schueller, Michael J. Housh, Alexandra B. Scott, Stephanie Benoit, Mary Powell, Avery Powell, Garren Ferrieri, Richard A. Examining the Effects of the Nitrogen Environment on Growth and N(2)-Fixation of Endophytic Herbaspirillum seropedicae in Maize Seedlings by Applying (11)C Radiotracing |
title | Examining the Effects of the Nitrogen Environment on Growth and N(2)-Fixation of Endophytic Herbaspirillum seropedicae in Maize Seedlings by Applying (11)C Radiotracing |
title_full | Examining the Effects of the Nitrogen Environment on Growth and N(2)-Fixation of Endophytic Herbaspirillum seropedicae in Maize Seedlings by Applying (11)C Radiotracing |
title_fullStr | Examining the Effects of the Nitrogen Environment on Growth and N(2)-Fixation of Endophytic Herbaspirillum seropedicae in Maize Seedlings by Applying (11)C Radiotracing |
title_full_unstemmed | Examining the Effects of the Nitrogen Environment on Growth and N(2)-Fixation of Endophytic Herbaspirillum seropedicae in Maize Seedlings by Applying (11)C Radiotracing |
title_short | Examining the Effects of the Nitrogen Environment on Growth and N(2)-Fixation of Endophytic Herbaspirillum seropedicae in Maize Seedlings by Applying (11)C Radiotracing |
title_sort | examining the effects of the nitrogen environment on growth and n(2)-fixation of endophytic herbaspirillum seropedicae in maize seedlings by applying (11)c radiotracing |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8401641/ https://www.ncbi.nlm.nih.gov/pubmed/34442661 http://dx.doi.org/10.3390/microorganisms9081582 |
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