Geosiphon and arbuscular mycorrhiza symbioses (Schüßler)
"
A clever person solves a problem. A wise person avoids it." Albert Einstein
Which are the main challenges for humankind in the next decades?
Problems in food production will become one of these, perhaps the most critical one. Within the next 50-100 years, global rock phosphate reserves will deplete.
The global peak P (the time point production will start to decrease due to resource depletion) is forecasted for 2040-2050 and the reserves of one of the biggest producers, the USA, is calculated to be already depleted in 2040. Rock phosphate is the primary, but limited source for large scale P-fertilization in agriculture, it is non-renewable, and currently without any practical or theoretical alternative. Despite this, as applied in high input agricultural systems in the USA and Europe, >60-80% of the P is just wasted. The situation is even more serious because fertile soil resources globally start to decline very soon - the 'peak soil' and 'peak phosphorous' will most likely happen earlier than the 'peak oil'. Each of these factors alone already might be disastrous for food-safety.
How to solve the problems? This is matter of debates, but it becomes increasingly evident that better understanding the arbuscular mycorrhiza (AM) symbiosis will play a large role in (urgently needed) sustainable agricultural practices: the AM is a key symbiosis for efficient P-uptake by plants. More than 80% of the land plants take up most of their needed P (and other nutrients) via an indirect uptake through the symbiotic AM fungi, efficiently exploring the soil, not by the roots themselves. In exchange, the plants supply large amounts of photosynthates (as sugars) to the fungi (which are a globally relevant CO2 sink). The nutrient exchange within plant root cells mainly takes place at the fungus-plant symbiotic interface formed around the finely branched fungal arbuscules (picture above), the name giving structure of the symbiosis.
Our group works on the arbuscular mycorrhiza (AM) and the Geosiphon symbiosis, with a focus on the fungal symbiosis-partners.
News: Press release (German) March 2012.
With the background of the fundamental role of the AM symbiosis in plant nutrition, we study the molecular base for the fungal nutrient transport. This regards the uptake as well as the release of inorganic nutrients, and sugars, by the fungi. The arbuscular mycorrhiza (AM) symbiosis is formed by plants and the obligate symbiotic, asexual, multinucleated AM fungi. These fungi (Glomeromycota) are difficult to study, but of enourmous importance in nearly all terrestrial ecosystems.
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The Geosiphon-Nostoc symbiosis is the only known endosymbiosis of a fungus with cyanobacteria. Intriguingly, the fungal partner belongs to the Glomeromycota, the AM forming fungi. This gives, on the one hand, important insights in the possible early evolution of the AM symbiosis. On the other hand, the Geosiphon-Nostoc symbiosis is used in our lab as a model system for the AM. This symbiosis of an AM fungus with a photosynthetically active prokaryote (cyanobacteria) is a worldwide unique tool to study the symbiotically expressed transcriptome of an AM fungus, the development of the symbiosis, and the nutrient uptake by the fungus.
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We also study the (molecular) biodiversity of AM fungi. DNA sequence data are used to develop molecular tools, including 454GS-FLX Titanium pyrosequencing approaches, for the 'molecular tracing' of AM fungi, which are otherwise hidden in the soil and in plant roots. The aim is to uncover possible functional preferences in plant-fungus associations and to identify suitable plant-fungus combinations for future sustainable agricultural management systems.
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The very first land plants already were associated with arbuscular mycorrhizal (AM) fungi. This symbiosis already existed before roots evolved! Therefore, this 'mycorrhiza' (fungus-root association) did not originate in the plant root, but in thalli of lower plants. Evolutionary, the AM fungi are much older than land plants. For land plants, including bryophytes, very basic mechanisms must exist to trigger their association with fungi of the Glomeromycota.
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Arbuscular mycorrhizal (AM) fungi harbour obligate symbiotic endobacteria related to Mycoplasma-containing clades of biotrophic bacteria. Intriguingly, AM fungal (AMF) andobacteria possess a Gram-positive appearing cell wall - as their ancestors, the Firmicutes - whereas the Mollicutes or Tenericutes (containing the mycoplasms) are characterized by lacking a cell wall.
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Up to date publications list from our group
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International project groups and consortia, individual projects
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Open PhD and students positions
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