Unlocking a high bacterial diversity in the coralloid root microbiome from the cycad genus Dioon

• Published in: PloS one Vol. 14; no. 2; p. e0211271
• Main Authors: Suárez-Moo, Pablo de Jesús, Vovides, Andrew P., Griffith, M. Patrick, Barona-Gómez, Francisco, Cibrián-Jaramillo, Angélica
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 06.02.2019; Public Library of Science (PLoS)
• Subjects: Analysis; Bacteria; Biodiversity; Biological evolution; Biology and Life Sciences; Botanical gardens; Composition; Cyanobacteria; Cycads; Cycas; Divergence; DNA, Ribosomal - genetics; Earth Sciences; Ecology and Environmental Sciences; Endophytes; Endophytes - classification; Endophytes - genetics; Endophytes - isolation & purification; Gene sequencing; Genera; Genes; Genomics; Laboratories; Legumes; Microbiological assay; Microbiomes; Morphology; Natural populations; Nitrogen fixation; Nitrogen-fixing bacteria; Nitrogen-Fixing Bacteria - classification; Nitrogen-Fixing Bacteria - genetics; Nitrogen-Fixing Bacteria - isolation & purification; Nostoc; Phylogenetics; Phylogeny; Plant growth; Plant Roots - microbiology; Population; Populations; Rhizosphere; RNA; RNA, Ribosomal, 16S - genetics; Roots; rRNA 16S; Sequence Analysis, DNA - methods; Soil sciences; Species diversity; Studies; Zamiaceae - classification; Zamiaceae - microbiology; Mexico
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0211271

Cycads are among the few plants that have developed specialized roots to host nitrogen-fixing bacteria. We describe the bacterial diversity of the coralloid roots from seven Dioon species and their surrounding rhizosphere and soil. Using 16S rRNA gene amplicon sequencing, we found that all coralloid roots are inhabited by a broad diversity of bacterial groups, including cyanobacteria and Rhizobiales among the most abundant groups. The diversity and composition of the endophytes are similar in the six Mexican species of Dioon that we evaluated, suggesting a recent divergence of Dioon populations and/or similar plant-driven restrictions in maintaining the coralloid root microbiome. Botanical garden samples and natural populations have a similar taxonomic composition, although the beta diversity differed between these populations. The rhizosphere surrounding the coralloid root serves as a reservoir and source of mostly diazotroph and plant growth-promoting groups that colonize the coralloid endosphere. In the case of cyanobacteria, the endosphere is enriched with Nostoc spp and Calothrix spp that are closely related to previously reported symbiont genera in cycads and other early divergent plants. The data reported here provide an in-depth taxonomic characterization of the bacterial community associated with coralloid root microbiome. The functional aspects of the endophytes, their biological interactions, and their evolutionary history are the next research step in this recently discovered diversity within the cycad coralloid root microbiome.