Title page for ETD etd-10022009-140919

Type of Document Dissertation
Author Brumfield, Kristy Marie
Author's Email Address kbrumf4@tigers.lsu.edu
URN etd-10022009-140919
Title Investigations of Chlamydomonas reinhardtii Ergosterol Biosynthesis
Degree Doctor of Philosophy (Ph.D.)
Department Biological Sciences
Advisory Committee
Advisor Name Title
Moroney, James V. Committee Chair
Bartlett, Sue Committee Member
Donze, David Committee Member
Longstreth, David J. Committee Member
Moore, Thomas S. Committee Member
Cooper, Richard Dean's Representative
  • lipid
  • sterol
  • Chlamydomonas reinhardtii
  • ergosterol
Date of Defense 2009-08-14
Availability unrestricted
Ergosterol is the major sterol found in the membranes of Chlamydomonas reinhardtii. While past studies have identified some ergosterol mutants in C. reinhardtii, very little is

known about sterol biosynthesis pathways in this species. With the elucidation of the Chlamydomonas genome, bioinformatics analysis has allowed us to determine potential genes involved in ergosterol biosynthesis. With this knowledge, a working model of the pathway was designed for future analysis. Several of the ergosterol biosynthetic genes were analyzed in respect to their role and involvement in flagellar regeneration. These genes were upregulated during the regrowth of the flagella. Also Chlamydomonas strains lacking flagella were analyzed by Q-RT PCR to determine what role ergosterol biosynthetic genes played in the absence of their flagella. Finally, one of the genes with

homology to the yeast sterol C-5 desaturase, ERG3, was chosen for further analysis. To test whether ERG3 of C. reinhardtii had a similar function, yeast Saccharomyces cerevisiae ERG3 knockout strains were created to assess whether a plasmid expressing the Chlamydomonas ERG3 could complement the deletion. These erg3 null mutants were transformed with a vector expressing ERG3 cDNA from C. reinhardtii driven by the yeast ADH1 promoter, and this expression was able to restore ergosterol biosynthesis and reverse phenotypes associated with lack of ERG3 function. Complementation of these erg3 null phenotypes strongly suggests that ERG3 in C. reinhardtii functions as a sterol C-5 desaturase. Results from this dissertation provides the groundwork for future experimentation in the field of sterol lipid research in Chlamydomonas reinhardtii.

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