Nodules and clocks: communication underground

Abstract:

Legumes house nitrogen-fixing endosymbiotic rhizobia in root nodules that are factories of metabolic activity whose activity is shaped by the plant, bacteria and environment. Our recent work has approached each of these components to understand how nodulation efficiency is shaped and controlled.

Nodules: By characterising microbial communities in Medicago truncatula inoculated with different rhizobial strains in three distinct soil types, we found that the rhizobial strain and symbiotic state can shape endosphere composition and plant nutrition. We also identified endosphere-located microbes whose abundance is associated with more efficient symbiosis and we are currently characterising interactions of these strains with both nodulating and non-nodulating plants.

Clocks: We found that the efficiency of symbiosis is affected by the plant circadian clock via LATE ELONGATED HYPOCOTYL (LHY) activity. Rhythmic LHY-regulated transcripts in root nodules include a subset of Nodule-specific Cysteine Rich peptides that may coordinate of bacterial activity with the rhythms of the plant host to ensure optimal symbiosis.

References:

Lagunas et al (2023) Rhizobial nitrogen fixation-efficiency shapes endosphere bacterial communities and Medicago truncatula host growth. Microbiome 11: 146.

Parkinson et al (2022) Polymer nanoparticles pass the plant interface. Nature Commun. 13: 7385.

Achom et al (2022) Plant clock control of Medicago truncatula nodulation involving regulation of Nodule Cysteine-Rich genes. Journal of Experimental Botany. 73: 2142-56.