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Sci Total Environ. 2016 May 15;553:32-41. doi: 10.1016/j.scitotenv.2016.02.078. Epub 2016 Feb 21.

Changes in rhizosphere bacterial gene expression following glyphosate treatment.

Author information

1
Department of Entomology and Plant Pathology, Auburn University, CASIC Building, Auburn, AL 36849, USA. Electronic address: ramsemm@auburn.edu.
2
School of Environment and Natural Resources, The Ohio State University, 2021 Coffey Road, Columbus, OH 43210, USA.
3
School of Agricultural Sciences, Northwest Missouri State University, 800 University Drive, Maryville, MO 64468, USA.
4
Department of Biological Sciences, Auburn University, CASIC Building, Auburn, AL 36849, USA.
5
Ag Spectrum, 428 East 11th Street, DeWitt, IA 52742, USA.
6
Department of Entomology and Plant Pathology, Auburn University, CASIC Building, Auburn, AL 36849, USA.

Abstract

In commercial agriculture, populations and interactions of rhizosphere microflora are potentially affected by the use of specific agrichemicals, possibly by affecting gene expression in these organisms. To investigate this, we examined changes in bacterial gene expression within the rhizosphere of glyphosate-tolerant corn (Zea mays) and soybean (Glycine max) in response to long-term glyphosate (PowerMAX™, Monsanto Company, MO, USA) treatment. A long-term glyphosate application study was carried out using rhizoboxes under greenhouse conditions with soil previously having no history of glyphosate exposure. Rhizosphere soil was collected from the rhizoboxes after four growing periods. Soil microbial community composition was analyzed using microbial phospholipid fatty acid (PLFA) analysis. Total RNA was extracted from rhizosphere soil, and samples were analyzed using RNA-Seq analysis. A total of 20-28 million bacterial sequences were obtained for each sample. Transcript abundance was compared between control and glyphosate-treated samples using edgeR. Overall rhizosphere bacterial metatranscriptomes were dominated by transcripts related to RNA and carbohydrate metabolism. We identified 67 differentially expressed bacterial transcripts from the rhizosphere. Transcripts downregulated following glyphosate treatment involved carbohydrate and amino acid metabolism, and upregulated transcripts involved protein metabolism and respiration. Additionally, bacterial transcripts involving nutrients, including iron, nitrogen, phosphorus, and potassium, were also affected by long-term glyphosate application. Overall, most bacterial and all fungal PLFA biomarkers decreased after glyphosate treatment compared to the control. These results demonstrate that long-term glyphosate use can affect rhizosphere bacterial activities and potentially shift bacterial community composition favoring more glyphosate-tolerant bacteria.

KEYWORDS:

Glyphosate; Metatranscriptome; Microbial community; RNA sequencing; Rhizosphere

PMID:
26901800
DOI:
10.1016/j.scitotenv.2016.02.078
[Indexed for MEDLINE]
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