S. pombe petites

Maria C.Costanzo mcc at proteome.com
Sun Feb 6 09:50:10 EST 2000

Dear Susan,

>I have a question regarding the respiratory pathway in fission yeast.  I
>seem to recall that there is evidence that the respiratory chain is
>essential for viability in fission yeast, not just for growth on
>non-fermentable carbon sources, but I don't recall for sure. This
>be in contrast to budding yeast where respiratory genes are not
>essential for growth on YPD. Am I remembering this correctly??  Can
>someone with a better memory refresh me on this subject? 

You do remember correctly.  Yeasts are classified as "petite-positive"
(i.e., they can survive the loss of their mitochondrial genome) or
"petite-negative" (loss of the mitochondrial genome is lethal). S.
pombe is petite-negative, while S. cerevisiae is petite-positive. It's
not respiration per se that is required for viability, though; S. pombe
can tolerate mutations in either the nuclear or mitochondrial genomes
that block respiration. It seems that in petite-negative yeasts loss of
the mitochondrial genome leads to leakiness of the inner membrane, and
this is lethal.  Des Clark-Walker has done elegant work on the
mechanism of this phenomenon, mostly in K. lactis, and there's a recent
review from his lab on the subject:

Chen XJ, Clark-Walker GD  The petite mutation in yeasts: 50 years on.
Int Rev Cytol 2000;194:197-238.


	Pascal Haffter found some years ago that mutations in two nuclear
genes of S. pombe allow it to survive loss of the mitochondrial genome
(Haffter P, Fox TD. Nuclear mutations in the petite-negative yeast
Schizosaccharomyces pombe allow growth of cells lacking mitochondrial
DNA. Genetics. 1992 Jun;131(2):255-60), but to my knowledge these genes
have not been molecularly identified.

Hope this is helpful!



Maria C. Costanzo, Ph.D.			

Editor, Fungal Knowledge Systems 		


100 Cummings Center, Suite 435M			

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