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Biotecnologia Aplicada
Elfos Scientiae
ISSN: 0684-4551
Vol. 13, Num. 3, 1996, pp. 216
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Biotecnologia Aplicada 1996 Volume 13 No. 3,
pp.216
EXPRESSION OF MITOCHONDRIAL GENES IN Neurospora
Crassa
Robert Brambl
Department of Plant Biology, University of Minnesota, USA.
Code Number:BA96094
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The germinating asexual spores (conidia) of Neurospora
crassa were employed to study steps in the accumulation of
transcripts of groups of mitochondrial genes, including those for
peptide subunits of cytochrome c oxidase (CO), ATPase (ATP), and
apocytochrome b (COB).
Physically clustered groups of genes were expressed as cohorts:
transcripts of the ATP8-ATP6-mtATP9-CO2 genes were almost
undetectable in the dormant spores, and they accumulated rapidly
as a group immediately after spore activation. Transcripts of COB
and the adjacent CO1 were abundant in the dormant spores; and,
the dormant and germinating spores contained size forms of the
COB transcripts that were not evident in vegetative cells.
Polyribosomes were prepared from mitochondrial lysates, and the
polyribosomal RNA was probed to identify the mRNAs of specific
genes; in several instances polycistronic mRNAs were present in
the polyribosomes as were the smaller end-products of the
inferred transcript processing pathways.
The expression of the physically dispersed genes for subunit
peptides of cytochrome c oxidase appears to be regulated at the
level of translation; these transcripts are accumulated in the
total mitochondrial RNA with sharply different kinetics, but they
appeared in the polyribosomes uniformly, their appearance
correlating with the uniform synthesis of the subunit
peptides.
Transcripts for a previously reported non-functional
mitochondrial gene, homologous to the functional nuclear gene for
ATPase subunit 9, were found in the germinating spores, but were
not detected in vegetative cells. These mtATP9 transcripts were
also present in the polyribosomes and were apparently translated
into a protein in vivo whose synthesis was insensitive to
cycloheximide and detectable with an anti-ATP9 subunit antibody.
Transcripts for two nuclear genes for mitochondrially localized
proteins, ATP9 and CO5, were accumulated in unison and especially
rapidly during spore germination.
Copyright 1996 Elfos Scientiae
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