Phosphate metabolism in arbuscular mycorrhizal fungi: a molecular approach
Arbuscular mycorrhizal (AM) fungi form symbiotic associations with most land plants and promote the growth of the host through enhanced uptake of phosphorus. Once the association is established, the fungi take up inorganic phosphate (Pi) from the soil through extraradical hyphae, accumulate Pi into vacuoles as polyphosphates (polyP) and translocate polyP to intraradical hyphae. This is assumed to be followed by hydrolysis of polyP and subsequent release of Pi into the plant-fungus interfacial apoplast (Ezawa et al., 2001). The molecular basis of these processes are not completely known as, up to now, just two Pi transporter genes has been isolated from AM fungi (M. Harrison & van Buuren, 1995; I.E. Maldonado Mendoza et al., 2001). In this work we used different approaches to identify genes involved in P metabolism in AM fungi. Degenerate primers were designed on conserved amino acid domains of Pi transporter and used in PCR experiments to amplify genomic DNA from AM spores. A fragment of 846 bp showing high similarity with Pi transporters was identified from the fungus Glomus mosseae (BEG12). Then the fragment was extended to 1186 bp using RACE experiments on G. mosseae external mycelium cDNA. In parallel experiments, a screening of a genomic library from Gigaspora margarita (BEG34) with a heterologous probe led to the isolation of a positive plaque which is currently under analysis. In addition, a clone showing high similarity with polyphosphate synthases was identified from an EST collection from germinated spores of Gigaspora margarita (BEG34). Taken in their whole, the results demonstrate that a number of PT transporter genes are present in AM fungi belonging to different taxa (Schubler et al., 2001) and some of them are surely expressed in presymbiotic and/or extraradical fungal structures. (Texte intégral)
| Main Authors: | , , |
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| Format: | conference_item biblioteca |
| Language: | eng |
| Published: |
CIRAD
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| Subjects: | P34 - Biologie du sol, mycorhizé à vésicule et arbuscule, métabolisme, phosphate, relation hôte pathogène, http://aims.fao.org/aos/agrovoc/c_24415, http://aims.fao.org/aos/agrovoc/c_4769, http://aims.fao.org/aos/agrovoc/c_35986, http://aims.fao.org/aos/agrovoc/c_34017, |
| Online Access: | http://agritrop.cirad.fr/490733/ |
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| Summary: | Arbuscular mycorrhizal (AM) fungi form symbiotic associations with most land plants and promote the growth of the host through enhanced uptake of phosphorus. Once the association is established, the fungi take up inorganic phosphate (Pi) from the soil through extraradical hyphae, accumulate Pi into vacuoles as polyphosphates (polyP) and translocate polyP to intraradical hyphae. This is assumed to be followed by hydrolysis of polyP and subsequent release of Pi into the plant-fungus interfacial apoplast (Ezawa et al., 2001). The molecular basis of these processes are not completely known as, up to now, just two Pi transporter genes has been isolated from AM fungi (M. Harrison & van Buuren, 1995; I.E. Maldonado Mendoza et al., 2001). In this work we used different approaches to identify genes involved in P metabolism in AM fungi. Degenerate primers were designed on conserved amino acid domains of Pi transporter and used in PCR experiments to amplify genomic DNA from AM spores. A fragment of 846 bp showing high similarity with Pi transporters was identified from the fungus Glomus mosseae (BEG12). Then the fragment was extended to 1186 bp using RACE experiments on G. mosseae external mycelium cDNA. In parallel experiments, a screening of a genomic library from Gigaspora margarita (BEG34) with a heterologous probe led to the isolation of a positive plaque which is currently under analysis. In addition, a clone showing high similarity with polyphosphate synthases was identified from an EST collection from germinated spores of Gigaspora margarita (BEG34). Taken in their whole, the results demonstrate that a number of PT transporter genes are present in AM fungi belonging to different taxa (Schubler et al., 2001) and some of them are surely expressed in presymbiotic and/or extraradical fungal structures. (Texte intégral) |
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