Macromolecule Synthesis and Breakdown in Relation to Sporulation and Meiosis in Yeast

Abstract

The time course of synthesis and breakdown of various macromolecules has been compared for sporulating ( a /α) and nonsporulating ( a/a and α/α) yeast cells transferred to potassium acetate sporulation medium. Both types of cells incorporate label into ribonucleic acid and protein. The gel electrophoresis patterns of proteins synthesized in sporulation medium are identical for sporulating and nonsporulating diploids; both are different from electropherograms of vegetative cells. Sporulating and nonsporulating strains differ with respect to deoxyribonucleic acid synthesis; no deoxyribonucleic acid is synthesized in the latter case, whereas the deoxyribonucleic acid complement is doubled in the former. Glycogen breakdown occurs only in sporulating strains. Breakdown of preexisting vegetative ribonucleic acid and protein molecules occurs much more extensively in sporulating than in nonsporulating cells. A timetable of these data is presented.

Protein Synthesis in Relation to Sporulation and Meiosis in Yeast

“…The hydrolyzed samples were precipitated with trichloroacetic acid, washed, and dried. The resulting pellet was analyzed for DNA content by the diaminobenzoic acid fluorimetric procedure as described previously (7). Symbols: K, 0, A, A, Fig.…”

“…At hourly intervals, 0.1-ml volumes of cells were fixed with 0.9 ml of a saline-formalin solution. The cells were collected by centrifugation, fixed to glass slides, and stained with Giemsa stain as described previously (7). by the addition of cycloheximide at 4 h when 7% of the cells are binucleate.…”

“…(iii) Intragenic recombination. Since AP-1a/a is an adenine auxotroph carrying noncomplementing mutations at the ade2 locus, one can measure intragenic recombination during meiosis and sporulation by determining the number of adenine prototrophs in the cultures (7). Figure 6 shows the effect of cycloheximide on this process.…”

“…In a previous communication (7), we described the chronological order of some of the physiological events occurring during meiosis and ascospore development in yeast. Some of these happen only in cells undergoing meiosis, whereas others are apparently part of a generalized response to the starvation conditions which induce sporulation.…”

“…Measurement of physiological parameters. The methods for measuring oxygen consumption, changes in the pH of the medium, protein and ribonucleic acid (RNA) breakdown, DNA synthesis, nuclear division, intragenic recombination, and glycogen content have been described (7). Protein and RNA synthesis were measured by pulse labeling, as described, with [31S Imethionine (0.75 mCi/umol) and ['H Jadenine (10 pCi/4mol), but 100 ,g of cycloheximide per ml was added to the pulse-labeling medium for cycloheximide-treated cultures.…”