Genetics. Published Articles Ahead of Print: December 6, 2006, Copyright © 2006
doi:10.1534/genetics.106.063081


A more recent version of this article appeared on February 1, 2007.

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Hybrid mitochondrial plasmids from senescence suppressor isolates of Neurospora intermedia

Marc F.P.M. Maas 1*, Rolf F. Hoekstra 2 and Alfons J.M. Debets 2

1 Centre Nationale de la Recherche Scientifique
2 Wageningen University

* To whom correspondence should be addressed. E-mail: maas{at}cgm.cnrs-gif.fr.

Submitted on July 7, 2006
Revised on August 17, 2006
Accepted on 14 November 2006


Abstract

We analyzed several natural suppressor isolates of the pKALILO-based fungal senescence syndrome of Neurospora intermedia. PKALILO did not increase in titer in these isolates. Neither did it show integration ]de novo'. In at least two of the senescence suppressor isolates, pKALILO had formed stable recombinants with other mitochondrial elements. PKALILO/mtDNA recombination junctions were complete and appeared to have been formed via non-homologous recombination mechanism. Further analysis revealed that it had recombined a novel, 2.6 Kb cryptic mitochondrial retroplasmid, similar to the mitochondrial retroplasmid pTHR1 from Trichoderma harzianum and retroplasmids of the 'Varkud' homology group. The recombinant molecules consisted of pKALILO, the novel element and short intervening stretches of mtDNA. The latter stretches clearly corresponded to 'in vivo' mitochondrial cDNA, suggesting the molecules had formed via the action of a template-switching reverse transcriptase. We discuss how different types of mitochondrial plasmids interact and their detrimental effect on the host may be suppressed.

Key Words: Aging, Kalilo, Retroelement, Senescence