Phylogenetic and population genetic evidence for positive selection in rapidly evolving plastid-nuclear enzyme complexes
| dc.contributor.author | Rockenbach, Kate, author | |
| dc.contributor.author | Sloan, Daniel, advisor | |
| dc.contributor.author | Argueso, Cris, committee member | |
| dc.contributor.author | Pilon, Marinus, committee member | |
| dc.contributor.author | Mueller, Rachel, committee member | |
| dc.date.accessioned | 2017-01-04T22:59:11Z | |
| dc.date.available | 2017-01-04T22:59:11Z | |
| dc.date.issued | 2016 | |
| dc.description.abstract | Rates of sequence evolution in plastid genomes are generally low, but numerous angiosperm lineages exhibit accelerated evolutionary rates in similar subsets of plastid genes. These genes include clpP1 and accD, which encode components of the caseinolytic protease (CLP) and acetyl-coA carboxylase (ACCase) complexes, respectively. Whether these extreme and repeated accelerations in rates of plastid genome evolution result from adaptive change in proteins (i.e., positive selection) or simply a loss of functional constraint (i.e., relaxed purifying selection) is a source of ongoing controversy. To address this, we have taken advantage of the multiple independent accelerations that have occurred within the genus Silene (Caryophyllaceae) by examining phylogenetic and population genetic variation in the nuclear genes that encode subunits of the CLP and ACCase complexes. We found that, in species with accelerated plastid genome evolution, the nuclear-encoded subunits in the CLP and ACCase complexes are also evolving rapidly, especially those involved in direct physical interactions with plastid-encoded proteins. A massive excess of nonsynonymous substitutions between species relative to levels of intraspecific polymorphism indicated a history of strong positive selection (particularly in CLP genes). Interestingly, however, some species are likely undergoing loss of the native (heteromeric) plastid ACCase and putative functional replacement by a duplicated cytosolic (homomeric) ACCase. Overall, the patterns of molecular evolution in these plastid-nuclear complexes are unusual for anciently conserved enzymes. They instead resemble cases of antagonistic co-evolution between pathogens and host immune genes. We discuss a possible role of plastid-nuclear conflict as a novel cause of accelerated evolution. | |
| dc.format.medium | born digital | |
| dc.format.medium | masters theses | |
| dc.identifier | Rockenbach_colostate_0053N_13912.pdf | |
| dc.identifier.uri | http://hdl.handle.net/10217/178872 | |
| dc.language | English | |
| dc.language.iso | eng | |
| dc.publisher | Colorado State University. Libraries | |
| dc.relation.ispartof | 2000-2019 | |
| dc.rights | Copyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright. | |
| dc.title | Phylogenetic and population genetic evidence for positive selection in rapidly evolving plastid-nuclear enzyme complexes | |
| dc.type | Text | |
| dcterms.rights.dpla | This Item is protected by copyright and/or related rights (https://rightsstatements.org/vocab/InC/1.0/). You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). | |
| thesis.degree.discipline | Cell and Molecular Biology | |
| thesis.degree.grantor | Colorado State University | |
| thesis.degree.level | Masters | |
| thesis.degree.name | Master of Science (M.S.) |
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