Importance of the SYM pathway in plant microbiomes

This BBSRC-funded project ran from Jan 2019-Dec 2022.

The common symbiosis (SYM) signalling pathway is shared between rhizobia and arbuscular mycorrhizal fungi. It controls the two most important symbiotic interactions between plants and microorganisms and is a critical factor in plant and agricultural yields. However, it is not understood how this pathway controls the wider microbiota of plant roots. Therefore, the role of SYM in determining the microbiota of M. truncatula will be assessed and whether this is controlled by the nitrogen or phosphorous status of the plant. Next the wider importance of the SYM pathway on microbiota composition will be determined by comparing the results from M. truncatula with that determined in a second legume (pea) and a cereal (rice). To move beyond cataloguing of microbiota composition to determine mechanisms of action a representative synthetic community of bacteria (SynCom) library of strains from the microbiota of M. truncatula will be assembled. This will enable the colonisation and stability of the SynCom to be determined. Members of the SynCom with altered colonisation of SYM mutants will be rigorously tested for their localisation on roots, initial adhesion, colonisation and chemoattraction to roots. Finally, the influence of SynCom members on plant growth will be assessed to facilitate future analysis.

Our specific work objectives are as follows:

I. Determine the role of the common SYM, Nod-specific and AM-specific pathways in selection of the root microbiota of M. truncatula, pea and rice.
II. Assemble a synthetic community (SynCom) from the main bacterial microbiota members of M. truncatula.
III. Determine the mechanism of SYM control of bacterial colonisation of M. truncatula roots.

Dr Andrzej Tkacz is the post-doctoral scientist working on this project.