Between Dec 19, 2024 and Jan 2, 2025, datasets can be submitted to DRUM but will not be processed until after the break. Staff will not be available to answer email during this period, and will not be able to provide DOIs until after Jan 2. If you are in need of a DOI during this period, consider Dryad or OpenICPSR. Submission responses to the UDC may also be delayed during this time.
 

Terminal differentiation of symbiotic rhizobia in certain legume species and its implications for legume-rhizobia coevolution.

Loading...
Thumbnail Image

Persistent link to this item

Statistics
View Statistics

Journal Title

Journal ISSN

Volume Title

Title

Terminal differentiation of symbiotic rhizobia in certain legume species and its implications for legume-rhizobia coevolution.

Published Date

2010-08

Publisher

Type

Thesis or Dissertation

Abstract

The symbiotic association between legume plants (Fabaceae) and nitrogen-fixing rhizobia is a classic system of cooperation, but with largely unexplored differences among species in life history traits. Rhizobia transform physiologically and morphologically into nitrogen-fixing bacteroids inside host nodules. The transformation is terminal (bacteroids are swollen and apparently nonreproductive) in some legume host species but not others, regardless of rhizobial genotype. The phylogenetic distribution of this host trait in the Papilionoideae subfamily of legumes suggests that the common ancestor of the papilionoids did not host terminally differentiated bacteroids and there appear to have been at least five independent origins of hosts imposing terminal differentiation on bacteroids. To consider possible advantages of this host trait, I compared the symbiotic efficiency of terminally and non-terminally differentiated bacteroids of a single rhizobial strain with dual-host capabilities. In the two available dual-host cases, I found greater fixation efficiency (N2 fixation per CO2 respiration) as well as plant return (host biomass) on investment per nodule mass in the hosts with terminal bacteroid differentiation than in those without. This suggests that host traits leading to terminal bacteroid differentiation may have been derived multiple times because of increased net symbiotic benefits to the host. Lastly, I tested whether legumes hosting terminally differentiated bacteroids impose sanctions, i.e. reduce benefits to the undifferentiated reproductive clonemates of less-mutualistic bacteroids in the same nodule. Host sanctions could maintain the evolutionary stability of the symbiosis despite "cheaters" - less-mutualistic rhizobia that potentially benefit from the fixation by other rhizobia sharing the same individual plant host. Legume roots were split so that half of each nodulated root system was exposed to nitrogen-free atmosphere (Ar:O2) to simulate cheating and the other half was in normal air (N2:O2). Rhizobial fitness (rhizobia per nodule) was compared between the two halves. A clear host sanctions effect in peas and alfalfa demonstrated that terminal differentiation of bacteroids does not compromise a legume host's ability to sanction. Differences in rhizobial life history suggest various rhizobial symbiotic traits for cooperation and cheating, perhaps leading to different mechanisms in different legume host species that maintain stability of the mutualism.

Description

University of Minnesota Ph.D. dissertation. August 2010. Major: Plant Biological Sciences. Advisor: R. Ford Denison. 1 computer file (PDF); vii, 114 pages.

Related to

Replaces

License

Collections

Series/Report Number

Funding information

Isbn identifier

Doi identifier

Previously Published Citation

Other identifiers

Suggested citation

Oono, Ryoko. (2010). Terminal differentiation of symbiotic rhizobia in certain legume species and its implications for legume-rhizobia coevolution.. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/97812.

Content distributed via the University Digital Conservancy may be subject to additional license and use restrictions applied by the depositor. By using these files, users agree to the Terms of Use. Materials in the UDC may contain content that is disturbing and/or harmful. For more information, please see our statement on harmful content in digital repositories.