Free access article

Issue Environ. Biosafety Res. Volume 4, Number 4, October-December 2005 Page(s) 235 - 242 DOI 10.1051/ebr:2006004 Published online 22 June 2006

Environ. Biosafety Res. 4 (2005) 235-242
DOI: 10.1051/ebr:2006004

Investigation of horizontal gene transfer in poplar/Amanita muscaria ectomycorrhizas

Chi Zhang, Rüdiger Hampp and Uwe Nehls

Universität Tübingen, Botanisches Institut, Physiologische Ökologie der Pflanzen, Auf der Morgenstelle 1, 72076 Tübingen, Germany

(Received March 21, 2005; accepted February 7, 2006; published online: 22 June 2006)

Abstract
Fine roots of forest trees form together with certain soil fungi symbiotic structures (ectomycorrhizas), where fungal hyphae are in intimate contact with plant cells. Due to root cell degeneration, plant DNA is released and could be taken up by the fungus. The possibility that horizontal gene transfer might result in a risk for the environment should be evaluated before a massive release of genetically engineered trees into nature occurs, even though only a few convincing examples of horizontal gene transfer are known. Transgenic poplars containing a construct of the Streptomyces hygroscopicus bar gene under the control of the Cochliobolus heterostrophus GPD (glyceraldehyde-3-phosphate dehydrogenase) promoter were generated by Agrobacterium-mediated transformation. The functionality of this construct in the ectomycorrhizal model fungus Amanita muscaria was previously verified by protoplast-based fungal transformation. 35 000 ectomycorrhizas, formed between transgenic poplars and non-transgenic A. muscaria hyphae, were isolated and transferred to selective agar plates. Putative herbicide-resistant fungal colonies were obtained after the first round of selection. However, none of these colonies survived a transfer onto fresh selection medium, nor did they contain the bar gene, indicating that no horizontal gene transfer from poplar to A. muscaria occurred during symbiosis under axenic conditions. However, since ectomycorrhizas are associated under natural conditions with viruses, bacteria and other fungi, these additional associations should be evaluated in future.

Key words: horizontal gene transfer / poplar / ectomycorrhiza / transformation

Corresponding author: Uwe Nehls uwe.nehls@uni-tuebingen.de

© ISBR, EDP Sciences 2006

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