Irregular Replication of Substoichiometric Mt DNA Copies

In contrast to the plastome, the hybrid chondriomes could also show patterns, which deviate from the parental types by a very high amplification of distinct mt genome regions. This was the case for an additional atp6-homologous sequence. By hybridization with the homologous probe containing atp6 the prominent additional fragment becomes visible in 10% of the somatic hybrids but not in their parents. Hybrids affected from this unregulated replication were found in the combinations of population II [a (+) g] and population IV [a (+) e]. An example for this occurence is given in the upper autoradiography. The same organisation was also found in the far related wild species S. polytrichon and S. verrucosum. The duplication differed from the original atp6 locus ("atp6_1") in the termination region 211 bp downstream from the stop codon ("atp6_2").

Parents of fusion population IV (lanes 1, 2), and hybrids (lane 3, 4) cut with EcoRI, hybridised with probe "atp6_1". In the deviating hybrid (lane 3) the blot makes visible a 3,4 kbp fragment, containing an additional atp6 gene with sequence deviation beginning 211 bp 3´ from stop codon. The signals of the lower bands represent the normal atp6/nad1 fragments.

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Loessl: Cytoplasm Genome Research
Andreas LÖSSL, 15.10.2010