Biological nitrogen fixation
Martin Parniske obtains ERC grant
LMU geneticist Professor Martin Parniske has been awarded an Advanced Investigator Grant worth up to 2.5 million euros by the European Research Council (ERC) to carry out a study of nitrogen fixation in plants. ERC Advanced Grants enable European researchers who have already made a mark in their respective fields to undertake innovative and high-risk projects.
In almost all terrestrial ecosystems, plant growth is limited by a lack of nitrogen. The atmosphere is rich in nitrogen gas, but plants cannot assimilate the element in this form. Instead, crop plants are fed nitrate (NO3) or ammonium (NH4) fertilizers to maintain yields. This in turn must be produced industrially by an energy-intensive and fossil fuel consuming chemical process that links fertilizer prices directly and food prices indirectly to the oil price. However, some of the species belonging to the related plant orders Fabales (legumes), Fagales (beeches), Cucurbitales (gourds) and Rosales (which includes the rose family) can form symbioses with soil bacteria that are able to fix atmospheric nitrogen and convert it enzymatically into ammonia. Successful symbiosis is preceded by an exchange of molecular signals between the bacteria and the roots of their prospective hosts, which induce the plant to form new plant organs, so-called root nodules that are colonized by the symbiotic bacteria and provide ideal conditions for nitrogen fixation.
A genetic predisposition to form such symbioses was probably present in the common ancestor of the four orders, but the actual ability to form root nodules developed independently in each. In his ERC project Martin Parniske plans to identify the genetic factors that enable representatives of the order Rosales to form a symbiosis with nitrogen-fixing bacteria of the genus Frankia because it infects a wide range of host species and can fix nitrogen in the presence of atmospheric concentrations of oxygen. These features discriminate Frankia from most rhizobia, the well known symbionts of legumes.
The order Rosales includes many well-known and economically important species, but contains very few that are capable of forming root nodules. Once the genes necessary for nodule formation have been identified, Parniske intends to introduce them into related species, such as the strawberry, which do not naturally produce nodules. This approach appears promising, because the strawberry genome, like those of apple and peach, has been sequenced completely. So Parniske and his colleagues can easily ascertain which of the genes necessary for symbiosis with Frankia are already present in these species by interrogating readily available genome databases. “Given that these species are considered genetically predisposed to form root nodules, they presumably lack only a few of the genes needed to establish a functional symbiosis,” Parniske explains. If he and his team manage to activate the signal relays that can unlock this potential, they will have taken a major step toward the ultimate goal of making agriculture more sustainable by reducing its dependence on artificial fertilizers.
Martin Parniske studied Microbiology, Botany, Biochemistry and Genetics in Konstanz and in Marburg, and obtained his PhD at Marburg University. After a postdoctoral stay at the Max Planck Institute for Plant Breeding Research in Cologne, he moved to the Sainsbury Laboratory in Norwich (UK), where he set up an independent research group in 1999. In 2004 he was appointed Professor of Genetics at LMU. göd