Comparative hormone profiling to underpin rhizobium symbiosis
In the legume-rhizobium symbiosis, formation of nitrogen-fixing root nodules is initiated upon perception of bacterial secreted lipo-chitooligosaccharides (LCOs). These so-called Nod-factors trigger the initiation of nodule primordia only in a specific zone of the root: the susceptible zone. The aim of my VENI project is to identify the hormonal landscape required for the creation of this susceptible zone.
Legumes evolved the rhizobium root nodule symbiosis ~60 million years ago (mya), followed by immediate massive evolutionary radiation. As a consequence the hormonal landscape of todays species may display variation that cannot be causally linked to Nod factor permissiveness. To identify such I will define the hormonal landscape of the model legume Medicago truncatula. Next, I will investigate constraints on this hormonal landscape by comparing the hormonal landscape of Medicago truncatula to the hormonal landscape of carefully selected other legume species, including some that cannot form root nodules. Despite evolutionary divergence, I hypothesize the occurrence of conservation in hormonal balances is relevant for establishing the susceptible zone. By identifying such conserved modules, I aim to deduce a conceptual hormonal landscape essential for the creation of the root susceptible zone in legumes.