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Rhizosheath microbial community assembly of sympatric desert speargrasses is independent of the plant host

Marasco, Ramona; Mosqueira, Mar�a J.; Fusi, Marco; Ramond, Jean-Baptiste; Merlino, Giuseppe; Booth, Jenny M.; Maggs-K�lling, Gillian; Cowan, Don A.; Daffonchio, Daniele

Authors

Ramona Marasco

Mar�a J. Mosqueira

Marco Fusi

Jean-Baptiste Ramond

Giuseppe Merlino

Jenny M. Booth

Gillian Maggs-K�lling

Don A. Cowan

Daniele Daffonchio



Abstract

Background
The rhizosheath-root system is an adaptive trait of sandy-desert speargrasses in response to unfavourable moisture and nutritional conditions. Under the deserts’ polyextreme conditions, plants interact with edaphic microorganisms that positively affect their fitness and resistance. However, the trophic simplicity and environmental harshness of desert ecosystems have previously been shown to strongly influence soil microbial community assembly. We hypothesize that sand-driven ecological filtering constrains the microbial recruitment processes in the speargrass rhizosheath-root niche, prevailing over the plant-induced selection.

Methods
Bacterial and fungal communities from the rhizosheath-root compartments (endosphere root tissues, rhizosheath and rhizosphere) of three Namib Desert speargrass species (Stipagrostis sabulicola, S. seelyae and Cladoraphis spinosa) along with bulk sand have been studied to test our hypothesis. To minimize the variability determined by edaphic and climatic factors, plants living in a single dune were studied. We assessed the role of plant species vs the sandy substrate on the recruitment and selection, phylogenetic diversity and co-occurrence microbial networks of the rhizosheath-root system microbial communities.

Results
Microorganisms associated with the speargrass rhizosheath-root system were recruited from the surrounding bulk sand population and were significantly enriched in the rhizosheath compartments (105 and 104 of bacterial 16S rRNA and fungal ITS copies per gram of sand to up to 108 and 107 copies per gram, respectively). Furthermore, each rhizosheath-root system compartment hosted a specific microbial community demonstrating strong niche-partitioning. The rhizosheath-root systems of the three speargrass species studied were dominated by desert-adapted Actinobacteria and Alphaproteobacteria (e.g. Lechevalieria, Streptomyces and Microvirga) as well as saprophytic Ascomycota fungi (e.g. Curvularia, Aspergillus and Thielavia). Our results clearly showed a random phylogenetic turnover of rhizosheath-root system associated microbial communities, independent of the plant species, where stochastic factors drive neutral assembly. Co-occurrence network analyses also indicated that the bacterial and fungal community members of the rhizosheath-root systems established a higher number of interactions than those in the barren bulk sand, suggesting that the former are more stable and functional than the latter.

Conclusion
Our study demonstrates that the rhizosheath-root system microbial communities of desert dune speargrasses are stochastically assembled and host-independent. This finding supports the concept that the selection determined by the desert sand prevails over that imposed by the genotype of the different plant species.

Citation

Marasco, R., Mosqueira, M. J., Fusi, M., Ramond, J., Merlino, G., Booth, J. M., Maggs-Kölling, G., Cowan, D. A., & Daffonchio, D. (2018). Rhizosheath microbial community assembly of sympatric desert speargrasses is independent of the plant host. Microbiome, 6(1), https://doi.org/10.1186/s40168-018-0597-y

Journal Article Type Article
Acceptance Date Nov 16, 2018
Online Publication Date Dec 4, 2018
Publication Date 2018-12
Deposit Date Apr 22, 2020
Publicly Available Date Apr 23, 2020
Journal Microbiome
Publisher BMC
Peer Reviewed Peer Reviewed
Volume 6
Issue 1
DOI https://doi.org/10.1186/s40168-018-0597-y
Keywords Rhizosheath-root system, Plant-microbe interactions, Speargrasses, Stochastic assembly, Holobiont, Desert environment, Microbiome
Public URL http://researchrepository.napier.ac.uk/Output/2654928

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Publisher Licence URL
http://creativecommons.org/licenses/by/4.0/

Copyright Statement
This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.





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