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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Disease and Pest Management Research Unit » Research » Publications at this Location » Publication #383101
Research Project: Integrated Disease Management of Exotic and Emerging Plant Diseases of Horticultural Crops

Location: Horticultural Crops Disease and Pest Management Research Unit

Title: Diversification of plasmids in a genus of pathogenic and nitrogen-fixing bacteria

Author
item WEISBERG, ALEX - Oregon State University
item MILLER, MARILYN - Oregon State University
item REAM, WALTER - Oregon State University
item Grunwald, Niklaus - Nik
item CHANG, JEFF - Oregon State University

Submitted to: Proceedings of the Royal Society. B. Biological Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2021
Publication Date: 11/29/2021
Citation: Weisberg, A.J., Miller, M., Ream, W., Grunwald, N.J., Chang, J.H. 2021. Diversification of plasmids in a genus of pathogenic and nitrogen-fixing bacteria. Proceedings of the Philosophical Transactions of The Royal Society B: Biological Sciences. 377(1842). Article 20200466. https://doi.org/10.1098/rstb.2020.0466.
DOI: https://doi.org/10.1098/rstb.2020.0466

Interpretive Summary: Two closely related genera of bacteria include Agrobacterium and Rhizobium. Rhizobia are asscoaited with plants facilitating symbiotic nitrogen fixation. In contrast, Agrobacterium are pahtogens causing galls on plants. Both species rely on small DNA elements called plasmids to engineer galls or nitrogen fixing root nodules. The extent to which these plasmids are shared and the consequences of their interactions on symbiosis phenotypes and bacterial evolution are not well understood. We extracted over 4,000 plasmid sequences from thousands of genome sequences of agrobacteria and rhizobia, including 14 newly sequenced. We used different scales of relatedness to construct a large network of these plasmids.In general, most groups of related plasmids are restricted to one or few genetic lineages of bacteria. Gall-inducing plasmids, in contrast, tend to have much broader ranges. We discuss the singificance of plasmid in this group.

Technical Abstract: Members of the agrobacteria-rhizobia complex have multiple and diverse plasmids, including those necessary for virulence and symbiotic nitrogen fixation. The extent to which these plasmids are shared and the consequences of their interactions on symbiosis phenotypes and bacterial evolution are not well understood. We extracted over 4,000 oncogenic, Sym, and accessory plasmid sequences from thousands of genome sequences of agrobacteria and rhizobia, including 14 newly sequenced. We used different scales of relatedness to construct a large network of these plasmids. In general, most groups of related plasmids are restricted to one or few bacterial lineages. Oncogenic plasmids, in contrast, tend to have much broader ranges. The network also revealed interactions that contributed to diversifying plasmids. Two new types of large mosaic oncogenic plasmids have incomplete virulence loci derived from three other types of oncogenic plasmids. The virulence loci in one of these types have both complementary and redundant sets of genes, suggesting the type emerged recently. Some of the newly discovered types emerged by recombining with accessory plasmids. The modularity and capacity for some plasmids to be transmitted broadly allow them to rapidly diversify and shape the evolution of plasmids and genomes across much of the agrobacteria-rhizobia complex.