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miami1132247140.pdf (3.72 MB)
ETD Abstract Container
Abstract Header
Evolution, Variation, and Excision of Developmentally Regulated DNA Elements in the Heterocystous Cyanobacteria
Author Info
Henson, Brian Junior
Permalink:
http://rave.ohiolink.edu/etdc/view?acc_num=miami1132247140
Abstract Details
Year and Degree
2005, Doctor of Philosophy, Miami University, Botany.
Abstract
In some cyanobacteria, heterocyst differentiation is accompanied by developmentally regulated DNA rearrangements that occur within the
nif
D,
fdx
N, and
hup
L genes, referred to as the
nif
D,
fdx
N, and
hup
L elements. These elements are excised from the genome by site-specific recombination during the latter stages of heterocyst differentiation. In this dissertation, two major questions are addressed: 1) what is the evolutionary history of the
nif
D and
hup
L elements and 2) how is the
nif
D element excised? To answer the first question, full length
nif
D and
hup
L element sequences were characterized and compared; and
xis
A and
xis
C sequences (which encode the recombinases that excise the
nif
D and
hup
L elements, respectively) were phylogenetically analyzed. Results indicated extensive structural and compositional variation within the
nif
D and
hup
L elements. The data suggests that the
nif
D and
hup
L elements are of viral origin and that they have variable patterns of evolution in the cyanobacteria. To answer the second question, a recombination system was devised where the ability of XisA to excise or recombine variants of the
nif
D element (substrate plasmids) was tested. Using PCR directed mutagenesis, specific nucleotides within the flanking regions of the
nif
D element were altered and the effects on recombination determined. Results indicate that nucleotides within and outside of the direct repeats are involved in excision, and that not all nucleotides within the direct repeats are required. In certain nucleotide positions, the presence of a purine versus a pyrimidine greatly affected recombination. Although excision was inhibited when certain nucleotides were mutated, PCR analyses revealed that excision occurred at a low level. The data also indicate that the site of excision occurs within the direct repeats. The results presented here suggest that the elements may be variable in size, composition, and excision.
Committee
Susan Barnum (Advisor)
Pages
126 p.
Keywords
Cyanobacteria
;
nifD element
;
hupL element
;
heterocyst differentiation
;
developmentally regulated DNA rearrangement
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Refworks
EndNote
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Citations
Henson, B. J. (2005).
Evolution, Variation, and Excision of Developmentally Regulated DNA Elements in the Heterocystous Cyanobacteria
[Doctoral dissertation, Miami University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=miami1132247140
APA Style (7th edition)
Henson, Brian.
Evolution, Variation, and Excision of Developmentally Regulated DNA Elements in the Heterocystous Cyanobacteria.
2005. Miami University, Doctoral dissertation.
OhioLINK Electronic Theses and Dissertations Center
, http://rave.ohiolink.edu/etdc/view?acc_num=miami1132247140.
MLA Style (8th edition)
Henson, Brian. "Evolution, Variation, and Excision of Developmentally Regulated DNA Elements in the Heterocystous Cyanobacteria." Doctoral dissertation, Miami University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=miami1132247140
Chicago Manual of Style (17th edition)
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Document number:
miami1132247140
Download Count:
598
Copyright Info
© 2005, all rights reserved.
This open access ETD is published by Miami University and OhioLINK.