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Evolution and ecology of the Ceanothus-Frankia symbiosis

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dc.contributor.advisor Myrold, David D.
dc.creator Jeong, Soon-Chun
dc.date.accessioned 2012-10-01T19:28:45Z
dc.date.available 2012-10-01T19:28:45Z
dc.date.copyright 1997-09-25
dc.date.issued 1997-09-25
dc.identifier.uri http://hdl.handle.net/1957/34006
dc.description Graduation date: 1998 en_US
dc.description.abstract The evolutionary relationship between Frankia and actinorhizal plants was evaluated by reconstructing molecular phylogenetic trees from nifH, 16S rDNA, and rbcL nucleotide sequences. Subgroupings in Frankia phylogenetic trees reconstructed from nifH and from 16S rDNA sequences were consistent in terms of plant origins of Frankia strains. Although the branching order of Frankia 16S rDNA and plant rbcL trees were different, subgroupings of Frankia and of plants correlated well in terms of symbiotic partnership. Tree matching, estimated divergence times, and molecular clock hypothesis tests indicated that Frankia clades diverged more recently than plant clades and that actinorhizal symbioses originated more than three times after the plant clades diverged. A phylogenetic tree of Ceanothus species, which are symbiotic partners of Frankia, was reconstructed using ndhF gene sequences. The analysis identified two main clades corresponding to two subgenera: Ceanothus and Cerastes. The analysis also suggested that three monophyletic clades within the subgenus ceanothus can be delimited on the basis of vegetative characters. Based on rbcL sequences, the two subgenera diverged 18-39 million years ago whereas species within each subgenus diverged more recently. These results support the current division of Ceanothus into two monophyletic subgenera and agree with the postulated recent divergence of many species within each subgenus. Specificity between Ceanothus species and their Frankia microsymbionts was evaluated by analysis of DNA in nodules collected from three copopulations of Ceanothus species. Sequencing of the intergenic spacer region between 16S and 23S rRNA genes suggested that Ceanothus-microsymbiont Frankia are closely related. Nodules were further analyzed by genomic fingerprinting using repetitive sequences and PCR (rep-PCR). A newly designed, direct repeat sequence and a BOX sequence showed that Ceanothus-microsymbiont Frankia exhibited less diversity within each copopulation than among copopulations. Furthermore, geographic separation was a more important factor for divergence of Ceanothus-microsymbiont Frankia than host plant. The population of Ceanothus-infective Frankia in soils under stands of Ceanothus velutinus and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), a non-host plant, were compared. The population sizes were measured using plant bioassay methods with C. velutinus, C. sanguineus, and C. integerrimus as trap plants. Population size in soil under C. velutinus was about 10 times higher than that under the Douglas-fir. Nodulation capacities of the three trap plants were not significantly different. The diversity of Frankia nodulating trap plants was examined using rep-PCR. Results suggested that infective Frankia is not species-specific with regard to the three Ceanothus species used as trap plants and that although the degree of diversity was similar in both soils, the two populations consisted of different Frankia. en_US
dc.language.iso en_US en_US
dc.subject.lcsh Ceanothus -- Evolution en_US
dc.subject.lcsh Ceanothus -- Ecology en_US
dc.subject.lcsh Frankia -- Evolution en_US
dc.subject.lcsh Frankia -- Ecology en_US
dc.subject.lcsh Actinorhizas en_US
dc.title Evolution and ecology of the Ceanothus-Frankia symbiosis en_US
dc.type Thesis/Dissertation en_US
dc.degree.name Doctor of Philosophy (Ph. D.) in Plant Pathology en_US
dc.degree.level Doctoral en_US
dc.degree.discipline Science en_US
dc.degree.grantor Oregon State University en_US
dc.contributor.committeemember Arp, Daniel
dc.contributor.committeemember Breen, Patrick
dc.contributor.committeemember Daeschel, Mark
dc.contributor.committeemember Steiner, Jeffrey
dc.description.digitization File scanned at 300 ppi (Monochrome, 256 Grayscale) using Capture Perfect 3.0 on a Canon DR-9050C in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR. en_US
dc.description.peerreview no en_us

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