Giles Oldroyd
Home Research Medicago trunculata as a model legume Genetic dissection of the Sym pathway Calcium as a secondary messenger in the Sym pathway Making a nodule The regulation of nodulation by hormones People Publications Contact Us

Infection thread in a wildtype plant

Spontaneous nodules induced by a CCaMK gain of function mutant

Spontaneous nodules induced by a CCaMK gain of function mutant.

Making a nodule

The nodule is a unique structure associated with symbiotic interactions with nitrogen fixing bacteria. The bacteria reside inside cells of the nodule, in an environment suitable for bacterial viability and nitrogen fixation.

Generating a nodule involves two main processes: the reinitiation of mitosis in cortical cells leading to the nodule primordium and the formation of infection threads that allow bacterial invasion into the developing nodule.

Infection threads are plant derived invasive invaginations of the cell that allow the transfer of rhizobial bacteria from the rhizosphere to the cortex of the root.

We have shown that the activation of the Sym pathway is sufficient to induce nodule formation, but is not sufficient to form infection threads. This is most likely due to the additional requirement for perception of exopolysaccarides on the surface of rhizobia for infection thread initiation. We are using genetics in Medicago truncatula to identify the plant components important for infection thread and nodule formation.