The STUDIA UNIVERSITATIS BABEŞ-BOLYAI issue article summary

The summary of the selected article appears at the bottom of the page. In order to get back to the contents of the issue this article belongs to you have to access the link from the title. In order to see all the articles of the archive which have as author/co-author one of the authors mentioned below, you have to access the link from the author's name.

  
       
         
    STUDIA BIOLOGIA - Issue no. 1 / 2019  
         
  Article:   POLYPLOIDY IN HALOPHILIC ARCHAEA: REGULATION, EVOLUTIONARY ADVANTAGES, AND GENE CONVERSION.

Authors:  JÖRG SOPPA. 		 
       
         
  Abstract:  Halophilic archaea are typically polyploid and contain more than 20 copies of the major chromosome. The chromosome copy number is regulated within the growth curve and in response to environmental conditions. Haloferax volcanii encodes 14 paralogs of a protein that is called Origin Recognition Complex (ORC) protein. A deletion analysis of orc genes revealed that three genes are essential and that all ORC proteins are involved in genome copy number regulation. Origins 1 and 2 of the major chromosome have been analyzed and showed very different strengths and regulatory features. Various potential evolutionary advantages for polyploidy in haloarchaea exist, and several advantages have been addressed experimentally. Examples are a high resistance against conditions that induce DNA double strand breaks (e.g. desiccation) and the usage of genomic DNA as a phosphate storage polymer. It has been hypothesized that the function of DNA as a phosphate storage polymer might have predated the function of DNA as genetic material in evolution. It was also suggested that polyploidy might explain the survival of haloarchaea in salt deposits over geological times, and indeed new isolates from an ancient salt deposit were found to be polyploid. At least under laboratory conditions heterozygous cells can easily be selected, which contain more than one type of chromosome. In the absence of selection it has been shown that intermolecular gene conversion leads to the equalization of genome copies. Gene conversion explains how haloarchaea can escape Muller’s ratchet and why homozygous mutants can easily be isolated or constructed.

Keywords: double strand break repair, gene conversion, Haloferax volcanii, origin recognition proteins, polyploidy. 		 
         
     
         
         
      Back to previous page