mitochondria, plastids and DNA inheritance

Mon Feb 14 22:40:07 EST 1994

>Subject: Mitochondria, Plastids and DNA inheritance

>" Direct evidence of plastid DNA and mitochondrial DNA in sperm cells
>in relation to biparental inheritance of organelle DNA in Pelargonium
>zonale by fluorescence electron microscopy" A Kuroiwa,et al  Eur J 
>Cell Biol  (1993) 62: 307-313
>According to this paper's abstract both plastids and mitochondria
>contain DNA and may show  biparental inheritance. 

>Two questions
>(1) Is there any other evidence that plastids contain unique DNA?
>(2) Is there any other evidence of biparental inheritance of
>non-nuclear DNA?  I thought maternal inheritance was obligatory. 

  Hurst and Hamilton (see Science 257:324 for a discussion) have
proposed on theoretical grounds that in order to avoid
intragenomic conflict (e.g. drive elements, killer factors)
between the two organelle genomes, evolutionary pressure would
lead to uniparental inheritance. Thus the organelle DNA from one
parent would always be eliminated and conflict avoided. Usually
the maternal contribution survives, but not always (conifers have
paternal inheritance). In protozoa, matings are often between two
similar cells (so neither is really "maternal"). However,
organelle DNA is usually inherited from only one parent. In
Chlamydomonas reinhardtii, the mitochondrial and the chloroplast
DNAs are each inherited from only one parent. The chloroplast DNA
is transmitted from the so called plus parent, but the
mitochondrial DNA is transmitted by the minus parent. 
  So Hurst and Hamilton would predict that biparental inheritance
of organelle DNA would be a rarity, which seems to be true.
I think inheritance of mitochondrial DNA in yeast is biparental
but my boss disagrees with me. Can anyone settle this?
  A further prediction of the model is that there should be a 
tendency to have only two sexes -- one that transmits and one
that does not.

>PS (I'm sure not to be alone in this :^)) What is a plastid?
>Jim Cummins                   

As in chloro-plastid.

Patrick Ferris

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