Understanding of the evolution of cooperation behavior of plant symbionts in the aim of the ecological intensification of agriculture – ECS

‘Mutualisms’ – cooperative interactions between different species – are central to the survival and reproduction of most organisms on earth, providing essential ecosystem services and playing a fundamental role in the creation and maintenance of biological diversity. Mutualistic symbioses have driven major evolutionary innovations, for example, the emergence of eukaryotes, likely an intracellular symbiosis between an archaeon and an alpha-proteobacterium. A huge diversity of mutualisms have emerged and evolved - many forms of symbioses have been described, but many remain a mystery.
The 450-million-year-old Arbuscular Mycorrhizal Fungal (AMF) mutualism is arguably the world’s most abundant mutualism. The AMF symbiosis is responsible for massive global nutrient transfer. Along with the nitrogen-fixing root nodule symbiosis, these relationships are considered to be the most important terrestrial symbioses ‘that help feed the world’ (Marx, Science 2004). Despite their ubiquity, these tremendous symbioses follow none of the constraints thought to select for the evolution of mutualism. In particular, horizontal transmission of symbionts among unrelated hosts and multiple symbiont genotypes per host facilitates ‘tragedy of the commons’ which refers to a dilemma described in an important article written by Hardin in Science (1968). The tragedy is that cooperative partners that supply their hosts with resources indirectly aid competing (non-cooperative) strains colonizing the same individual. As a result, cheaters are predicted to spread at the expense of cooperators, therein destabilizing the mutualism (West et al., 2002). Observations from agricultural systems demonstrate the persistence of less-mutualistic symbionts for both Rhizobia and AM fungi. Building upon this work, our ECS project will explore cooperation in plant symbioses, specifically exploring how plant-microbe interactions shape the ecological processes and evolutionary trajectories of natural and agricultural ecosystems. This work will also focus on possible novel symbioses. This work is anticipated to have tremendous importance for designing a more ecologically intensive agriculture (Kiers et al. Science 2008). The project submitted will provide new knowledge and perspectives on the erosion of plant diversity, and its consequences for consortiums of symbiotic microorganisms.
As root symbionts are crucial components of ecosystem functioning and in the maintenance of global soil fertility, our work is likely to lead to broader impacts in soil protection policy, plant breeding research and the design of sustainable agricultural systems.

Our proposed work is supported by established collaborations with leading international scientists. The French laboratories will collaborate with one laboratory in Netherlands (Vrije Universiteit, Amsterdam), one in Germany and two laboratories in the USA.
The ECS project is subdivided onto 5 tasks (Cooperative behaviour evolution & diversity of microorganisms colonising plant-roots; Plant development behaviour, endophyte and other symbionts; Toward a better understanding of the symbiotic interactions in roots; Modelling the dynamics of root-associated microorganisms & the evolution of cooperative behaviour by a constraint programming approach; Toward a better use of ecological functions of symbionts in agriculture to maintain soil fertility).

The aims of this project fit perfectly to the call ‘SYSTERRA’ especially within the thematic axis ‘intensification écologique des systèmes de production' sub axis ‘concevoir le pilotage des fonctions écologiques des sols' but also sub-axis 'élaborer de nouvelles techniques d'agriculture de précision concourant à une gestion écologiquement intensive de la production agricole'.