Desert plant microbiome

Microbes do not exist in seclusion but form complex interactions within- and among-microbial kingdoms. Among these, symbiotic associations with mycorrhizal fungi and nitrogen-fixing bacteria are known to improve plant health, and provide resources to other microbial members. However, how these symbionts interact between each other and their impact on the extended microbiota remains elusive. Using an extensive co-occurrence network approach on 689 rhizosphere and roots samples of six species in a natural desert environment, we described how these symbionts were structural to the plant microbiota. We found that the plant species was a strong driver of its microbiota composition and on the specificity of its interactions at the OTU or ASV level. Despite this specificity, a covariance structure was conserved across all networks: mycorrhizal fungi strongly covaried with fungi other mycorrhizal fungi, especially in plant roots, a pattern known as assortativity. This structural property, already described in the gut microbiota but not in plants reflects their ecological niche preference. On the other side, Rhizobiales and Frankiales covaried with other bacteria and fungi, and were highly structural to the single- and multi-kingdoms networks. Through this extensive cooccurence network analysis of plant microbiota, and the study of symbiont assortativity, we provide further evidence of the importance of fungal symbionts in structuring the global plant microbiota.