Sanders Group - Ecology and Evolution of Symbiotic Organisms

For more information about mycorrhizas, our research projects in Lausanne and in the field in Colombia, with lots of photos and animations please visit:

http://people.unil.ch/iansanders/

© Dr. Zigmunds Orlovskis

Symbiotic interactions between different species are extremely common in nature and have evolved many times independently throughout the history of life. The abundance of symbiotic interactions indicates that this is clearly a very successful life strategy. Some symbioses are very important for the functioning of ecosystems. The interaction between plants and mycorrhizal fungi is necessary for plants to obtain sufficient phosphorus and other nutrients and it plays a key role in global carbon and phosphorus cycles.

Most of our work is carried out on the mycorrhizal symbiosis, and particularly the fungal side of the partnership. At least 60% of the world's plant species and all our globally important crops form this symbiosis. Global phosphate reserves are likely to become critically low in the next decades and prices are will escalate, along with the rapid growth of the world's human population.
It is essential to understand the biology of this symbiosis because of it's ubiquity in nature and it's importance for plant growth, agriculture, plant biodiversity and ecosystem stability and productivity. This is essential for conserving phosphate and for feeding people in the future.

In recent years, our group has focussed on furthering the basic understanding of the genetics, ecology and molecular biology of the mycorrhizal symbiosis. This particularly concerns the unusual genetics of the fungal partner in this symbiosis. We then apply this scientific knowledge in developing countries (especially Colombia), using mycorrhizal fungi to increase agricultural production of globally important crops and, at the same time, reduce fertiliser inputs. The ultimate goal of the applied part of our research is to reduce poverty and hunger. Because the mycorrhizal symbiosis is also important for healthy functioning of ecosystems, we also conduct ecological experiments aimed at understanding the mechanisms by which mycorrhizal fungal genetics contributes to plant diversity in ecosystems.

The genetics of arbuscular mycorrhizal fungi is unusual (see Sanders & Croll, 2010, Annual Review of Genetics). The fungi are coenocytic meaning that there are no membranes separating one nucleus from another. We have demonstrated that the nuclei are genetically different from each other within the same fungus/individual (see Kuhn et al., 2001, Nature and Hijri & Sanders, 2005, Nature). We study the consequences of this among-nucleus genetic diversity on the symbiosis and on how plants grow (see below).

It was thought that mycorrhizal fungi are completely clonal, exhibiting no genetic exchange and segregation. One of the most exciting findings in our group is that these two genetic processes indeed occur in mycorrhizal fungi and that they can have very large effects on plant growth. In the greenhouse, we can increase rice growth by up to five times by inoculating the plants with genetically novel fungi created in our lab using the completely natural processes of genetic exchange and segregation (see Angelard et al. 2010).

Plants have an enormous difficulty obtaining phosphorus. This is especially the case in most tropical soils, where farmers have to apply huge amounts of phosphate fertiliser. In the tropics, mycorrhizal fungi can make a major impact in agriculture and reduce fertiliser costs. Our research has taken an exciting turn in the last couple of years, allowing us to apply our technological developments in improving mycorrhizal fungi and using them to reduce farmers costs in the tropics. We have teamed up with Prof. Alia Rodriguez's group at the National University of Colombia and with the Spanish biotechnology company Mycovitro S.L. to develop biotechnologically in-vitro produced mycorrhizal fungal lines for use with globally important crops. Our applied work in the field is mostly on cassava as globally it is one of the most important food security crops.