Microarray-directed development of biomarkers indicating aluminium stress in trees

Poplar cultivated in a hydroponic system. Photo: Nadine Grisel.

Poplar microarray hybridized with RNA isolated from rooted poplar cuttings treated with Al. Photo: FGCZ.

Mobilization of aluminium in acidic soils is regarded as a health threat to many European forests. In this project, we are developing biomarkers indicating Al exposure and effects by capitalizing on genome resources recently established for forest trees.

Background

Aluminium (Al) is a highly abundant metal which is innocuous at neutral and weakly acidic soil conditions. As soils become more acidic as a result of natural processes or acid deposition, Al is dissolved into toxic Al cations. This form of Al can inhibit root growth at micromolar concentrations resulting in a reduced and damaged root system.
Due to continuing deposition of acidifying compounds, soil acidification and its associated dissolution of Al are regarded as a health threat to many European forests. Because soil acidification not only leads to Al mobilization but also to the depletion of base cations (BC), the molar ratio of BC:Al is widely used as an indicator of soil acidification and potential Al toxicity. However, the utility of this indicator is increasingly questioned, and there is a widespread agreement that biomarkers are needed which reflect physiological changes following Al exposure.

Aims

This project aims at the development of biomarkers indicating Al exposure and effects by capitalizing on genome resources recently established for forest trees. The project is carried out within the frame of the COST Action E38 “Woody Root Processes”.

Methods

As a model tree species, we are using poplar for which the entire genome has been deciphered. Biomarkers will be established based on Al-responsive genes. Such genes will be identified by application of microarrays to poplar treated with Al under controlled conditions. Isolated Al-responsive genes will be used to design easy-to-use biomarkers. The established biomarkers will be validated in greenhouse experiments with poplar cultivated on acidic soils with high concentrations of Al in the soil solution.

Partners

• Nadine Grisel, Ivano Brunner (WSL)
• Jean-Pierre Métraux and Lucien Bovet (University of Fribourg)
• Marzanna Künzli-Gontarczyk and Ulrich Wagner (Functional Genomics Center Zurich, FGCZ)

The project is part of the dissertation of Nadine Grisel.