The Function of TAR1 and the Evolution of the Retrograde Response
Thesis DisciplineBiological Sciences
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
TAR1 is a protein coding gene situated antisense to the 25S rRNA in S. cerevisiae. Tar1p is localized to the mitochondrial inner membrane, and expression is enhanced under conditions of respiratory dysfunction. One common cause of respiratory dysfunction in S. cerevisiae are selfish mitochondrial mutants known as ρ- mitotypes. ρ- mitotypes exhibit drive within the cell following sexual reproduction ; outcompeting host cells and inducing respiratory dysfunction. Respiratory dysfunction activates the Retrograde Response, which involves the expression of genes to compensate for loss of anabolic activity that accompanies respiratory dysfunction. The Retrograde Response also leads to the formation of lifespan shortening Extrachromosomal rDNA circles. Amplification of rDNA circles has the effect of increasing TAR1 at the same time as lifting transcription repression. This observation led to the hypothesis that the formation of rDNA circles was a positive effect of the Retrograde Response, and that TAR1 may serve to ameoleriate the spread of respiratory incompetent mitochondria following sexual reproduction. In this thesis, experiments are conducted that show that TAR1 does suppress the drive of selfish mitochondrial mutants. Additional bioinformatic analyses show that the Retrograde Response may be a recent adaption to selfish mitochondrial mutants.