New Cytoplasmic Genetic Element That Controls 20S RNA Synthesis During Sporulation in Yeast

Under conditions that induce meiosis and sporulation in Saccharomyces cerevisiae, most strains accumulate a 20S RNA, amounting to as much as 15% of the newly synthesized RNA. The ability of cells to accumulate this new RNA species depends on a dominant genetic element that is cytoplasmically inherited, but is distinct from the other cytoplasmic elements that have been previously identified. The ability to synthesize 20S RNA does not depend on mitochondrial DNA, 2-micron DNA, the translational suppressor psi, the genetic element carrying URE3, or double-stranded killer RNA. However, all 20S- strains examined were also nonkillers, although many nonkiller strains were 20S+. This work also shows that 20S RNA accumulating is not essential for sporulation even though it is induced only by conditions that initiate sporulation. Furthermore, strains that are unable to complete meiosis are still capable of producing 20S RNA when placed under the nitrogen starvation conditions that promote sporulation.