mitochondria, plastids and DNA inheritance

Elizabeth Harris chlamy at
Tue Feb 22 10:05:42 EST 1994

In article <2kbt1n$ie8 at>,
pw at (Paul Wakenight) wrote:
> I have a few questions.  What is the fate of paternal plastid DNA?
> If it is transmitted into the egg (as mentionned earlier) is it able
> to enter the respective plastid?  How does it know which plastid to enter?
> It seems to me that PCR could be applied to fractionated eggs immediately 
> following fertilization to answer these questions.
> Also, wouldn't diploidy in plastids and the adaptive advantages of recombi-
> nation require mitotic machinery similar to that in the nucleus?  Also, what
> selective advantage could arise from dipl. - is it wrong to assume that      
> plastids have approached maximal effectiveness for their given function?

In the land plants that have biparental inheritance of plastid DNA, whole
plastids seem to be transmitted through the pollen, and recombination of
plastid DNA is rare.  During mitotic division, the plastids are apportioned
between the daughter cells.  There doesn't seem to be any specific mitotic
machinery that ensures a certain number go to each daughter cell, however. 

In the green alga Chlamydomonas reinhardtii, which has only a single
chloroplast and has a simple sexual cycle involving fusion of two similar
gametes of opposite mating types, the chloroplasts fuse within a few hours
of cellular fusion.  In most cells, chloroplast DNA from the one parent is
then degraded.  However, in exceptional cases (which can be increased
experimentally), it is maintained, and recombination does occur between
chloroplast DNA molecules.

Some additional references:

Coleman, A.W. (1982).  Sex is dangerous in a world of potential symbionts
or the basis of selection for uniparental inheritance.  J. Theor. Biol. 97,

Goodenough, U.W. (1985).  An essay on the origins and evolution of
eukaryotic sex.  In: The Origin and Evolution of Sex, ed. H.O. Halvorson
and A. Monroy, MBL Lectures in Biology, Vol. 7, Alan R. Liss, New York. 
pp. 123-140.

Gillham, N.W., J.E. Boynton, and E.H. Harris (1991).  Transmission of
Plastid Genes.  In: The Molecular Biology of Plastids.  Cell Culture and
Somatic Cell Genetics of Plants, Vol. 7A.  eds. L. Bogorad and I.K. Vasil,
Academic Press, San Diego.  pp. 55-92.

Elizabeth Harris
chlamy at

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