Propagation of a Novel Cytoplasmic, Infectious and Deleterious Determinant Is Controlled by Translational Accuracy in Podospora anserina

Corresponding author: Philippe Silar, Institut de Génétique et Microbiologie, URA 2225, Université de Paris Sud, 91405 Orsay cedex, France., silar{at}igmors.u-psud.fr (E-mail)

Communicating editor: A. G. HINNEBUSCH

Some mutant strains of the filamentous fungus Podospora anserina spontaneously present a growth impairment, which has been called Crippled Growth (CG). CG is caused by a cytoplasmic and infectious factor, C. C is efficiently transmitted during mitosis but is not transmitted to the progeny after sexual crosses. C is induced by stationary phase and cured by various means, most of which stress the cells. Translational accuracy is shown to tightly regulate the propagation of C during the active growth period, because its propagation in dividing hyphae is restricted to cells that display an increased translational accuracy. However, induction of C in stationary phase proceeds independently from the translational accuracy status of the strain. CG does not seem to be accompanied by mitochondrial DNA modifications, although C activates the action of the Determinant of Senescence, another cytoplasmic and infectious element, which causes a disorganization of the mitochondrial genome. In addition, presence of C drastically modifies the spectrum of the mitochondrial DNA rearrangements in AS6-5 mat- cultures during Senescence. C seems to belong to the growing list of unconventional genetic elements. The biological significance of such elements is discussed.

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