Kurzbeschreibung
(Englisch)
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Aluminium (Al) is considered an important factor affecting the health of forest trees on acidic soils. The potential risk of Al for trees is mainly assessed by quantification of exchangeable Al concentrations in the soil, but the interpretation of these data in biological terms is often difficult. In the proposed project, we will develop sensitive and efficient biomarkers indicating Al stress, based on information gained from microarray analyses.
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Partner und Internationale Organisationen
(Englisch)
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BE, CH, CZ, DE, EE, ES, FI, FR, GR, IE, IL, IT, LV, NL, NO, PL, PT, SE, SI, SK, TR, UK
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Abstract
(Englisch)
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Forest soils in temperate regions can be very acidic, especially when natural acidification is augmented by acids deposited from atmospheric pollutants. As a result of soil acidification, the rhizotoxic aluminium (Al) can be released into the soil solution to levels that inhibit root growth. Despite the general concern of Al toxicity in forests, biological markers indicating Al exposure and effects are not available. In this project, we aimed to identify genes that are suitable to develop biomarkers. Aspen (Populus tremula) was used as a model tree because of the availability of the genome resources for Populus. Application of the GenChip poplar genome array to roots of aspen treated with Al for 6 h, 2 d, and 10 d revealed 175 induced and 69 suppressed genes. The majority of these genes were regulated at 6 h, presumably reflecting root growth, which was strongly inhibited at 6 h and partially was recovered at 2 d and 10 d. Enrichment analysis identified sets of functionally related genes whose members were statistically over-represented compared to the genes on the genome array. These sets included genes related to cell wall modification, oxidative stress, cell death, and transport processes. Two of the genes involved in transport were related to the Arabidopsis Al tolerance genes AtALS3 (aluminum sensitive 3), possibly mediating the redistribution of Al, and AtMATE (multi-drug and toxin extrusion), facilitating the exudation of citrate. Expression patterns of the two aspen genes in different plant tissues and in response to Al were highly coherent with that of AtALS3 and AtMATE, suggesting that we have isolated homologs of the two Arabidopsis genes. The expression of PtALS3 and PtMATE was further analysed in roots of aspen cultivated in weakly and strongly acidic soils. The analysis showed that the expression of the two genes increases with the Al in the soil solution. PtALS3 and PtMATE are thus valuable candidates to develop easy-to-use biomarkers for testing the Al status of forest soils.
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