Temporal Action of Mutations Inhibiting the Accomplishment of Quiescence or Disrupting Development in the Fungus PODOSPORA ANSERINA.

Two Podospora mutants carrying mutations modE and modF were persumed to be quiescent defective, because, when grown under glucose limitation, they differed from the wild-type strain in an excess of dry weight production and a reduction of cell survival. New insight on the action of modE and modF mutations was provided by the study of double mutants resulting from the association of modE or modF mutations with unrelated developmental mutations.-ModE and modF were first coupled to three allelic mutations ( modC) that inhibit production of all hyphal cell derivatives (late ramifications, aerial hyphae and protoperithecia). Suppression in the double mutants of the excess of proliferation associated with modE and modF and restoration of normal cell survival indicated that modE and modF result in an uncontrolled production of hyphal cell derivatives in which deregulation is presumed to be responsible for the reduction of cell survival following glucose exhaustion.-ModE and modF were associated with mutations of two genes (modD and modG) which abolish production of hyphal cell derivatives (like modC mutations) but also inhibit the renewal of growth of cells situated in the center of colonies. Investigations of eight of these double mutants showed that modE and modF mutations suppress the inhibitory action of modD and modG on production of hyphal cell derivatives and on growth renewal.-Taken together these results lead to the suggestion that the accomplishment of a quiescent state for cell survival under glucose starvation is the final stage in the differentiation of hyphal cells and prerequisite for the production of derivatives of hyphal cells and for a control of their development.