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Specialized Replication Operons Control Rhizobial Plasmid Copy Number in Developing Symbiotic Cells

The rhizobium – legume symbiosis is a complex process that involves genetic cooperation from both bacteria and plants. Previously, our lab described naturally occurring accessory plasmids in rhizobia that inhibit this cooperation. A transposon mutagenesis was performed on the plasmids to detect the genetic factor that blocked nitrogen fixation. Several of the plasmids were found to possess a replication operon that when disrupted by transposon insertion, restored symbiotic function. This study describes an in-depth investigation into one of those plasmids, pHRC377, and into its replication operon. The operon, which we have called repA2C2, comes from the repABC family of replication and partitioning systems commonly found in alphaproteobacteria. In this study we show that this operon is not necessary for pHRC377 replication in LB culture or free living cells, but is necessary for plasmid amplification in the plant, specifically during rhizobial differentiation into nitrogen fixing bacteroids. We also show how the other repABC type operons on pHRC377 function in relation to plasmid maintenance and copy number during endoreduplication and how they do not have the same phenotypic effect as repA2C2.

Identiferoai:union.ndltd.org:BGMYU2/oai:scholarsarchive.byu.edu:etd-7167
Date01 December 2015
CreatorsPerry, Clarice Lorraine
PublisherBYU ScholarsArchive
Source SetsBrigham Young University
Detected LanguageEnglish
Typetext
Formatapplication/pdf
SourceAll Theses and Dissertations
Rightshttp://lib.byu.edu/about/copyright/

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