The core meiotic transcriptome in budding yeasts.

We used high-density oligonucleotide microarrays to analyse the genomes and meiotic expression patterns of two yeast strains, SK1 and W303, that display distinct kinetics and efficiencies of sporulation. Hybridization of genomic DNA to arrays revealed numerous gene deletions and polymorphisms in both backgrounds. The expression analysis yielded approximately 1,600 meiotically regulated genes in each strain, with a core set of approximately 60% displaying similar patterns in both strains. Most of these (95%) are MATa/MATalpha-dependent and are not similarly expressed in near-isogenic meiosis-deficient controls. The transcript profiles correlate with the distribution of defined meiotic promoter elements and with the time of known gene function.

The SPO1 gene product required for meiosis in yeast has a high similarity to phospholipase B enzymes.

The SPO1 gene of Saccharomyces cerevisiae has been cloned and sequenced. The Spo1 protein reveals significant similarity with fungal phospholipase B (PLB) enzymes. Features of the SPO1 gene sequence are presented.

[Repair of a double-stranded gap in plasmid DNA in radiosensitive mutants of Saccharomyces cerevisiae: effectiveness and precision]. / Reparatsiia dvunitevykh breshei plazmidnoi DNK u radiochuvstvitel'nykh mutantov Saccharomyces cerevisiae: éffektivnost' i tochnost'.

The repair of a double strand gap in plasmid DNA in radiosensitive mutants of Saccharomyces cerevisiae has been studied. The proportion of repair events resulting in the complete doublestrand gap recovery of the plasmid DNA has been found to be close to 100% in Rad+ cells. The mutation rad55 did not interfere in the doublestrand gap repair efficiency and accuracy. The mutant rad57 is capable of the effective doublestrand gap repair without restoration of the DNA sequence deleted by the gap. The mutation rad53 substantially inhibited the efficiency of the doublestrand gap repair but did not influence the accuracy of the repair. Plasmid DNA doublestranded gap repair is completely blocked by mutations rad50 and rad54.

[Cloning and identification of the gene controlling nitrogen metabolism in the photosynthetic purple bacteria Rhodobacter sphaeroides]. / Klonirovanie i identifikatsiia gena, kontroliruiushchego azotistyi metabolizm u fotosinteziruiushchei purpurnoi bakterii Rhodobacter sphaeroides.

A recombinant plasmid has been selected from the genomic library of Rhodobacter sphaeroides that restores the properties of the wild type strain in the mutant Drn121. The latter possesses the derepressed synthesis of nitrogenase when grown in the light, inability of nitrogen fixation in the dark and growth on potassium nitrate as a single source of nitrogen, disruption of ammonium ions and methylamine transportation, decreased activity of glutamine synthetase. The gene complementing the drn121 mutation is localized within the EcoRI-HindIII fragment of Rhodobacter sphaeroides chromosome 2.25 kb in size. Analysis of the fragment nucleotide sequence has revealed the fragments with a high level of homology to regulatory genes ntrB (the 3'-end) and ntrC of Rhodobacter capsulatus. The plasmid pRCN102, containing the nifR3-ntrB-ntrC operon of Rhodobacter capsulatus, is able to complement the drn121 mutation while its derivatives having inactivated ntrN or ntrC genes are not. Hence, in Rhodobacter sphaeroides mutant Drn121 the mutation is localized in ntrC gene the product of which is involved not only in nitrogen fixation but also in nitrogen metabolism on the whole.

Spo1, a phospholipase B homolog, is required for spindle pole body duplication during meiosis in Saccharomyces cerevisiae.

The SPO1 gene was cloned and shown to encode an early meiotic transcript specifying a nuclear protein with extensive similarity to fungal and vertebrate phospholipase enzymes. Alteration of a conserved serine residue in the putative phospholipase active site, and presence of the spo1-1 temperature-sensitive mutation, which resides near this site, each result in loss of SPO1 function. The phenotype of a complete deletion indicates that SPO1 is dispensable for vegetative growth, premeiotic DNA synthesis and meiotic recombination. In contrast, it is required for Meiosis I (MI) and Meiosis II (MII) chromosome segregation and spore formation. In a null mutant approximately 75% of cells arrest early at MI spindle pole body (SPB) duplication, approximately 20% arrest at MII, and approximately 5% arrest at spore formation. Progression beyond the first arrest point suggests the existence of functions partially redundant to Spo1 and that Spo1 is required at multiple stages. At present SPO1 is the only known gene required for SPB duplication in meiosis but not in mitosis. Its product may thus play a regulatory (rather than a structural) role in SPB function. The transcriptional program in the spo1 null is similar to the wild type early in meiosis but is significantly delayed at later stages of sporulation. A single gene, CWP1, was recovered as a multicopy suppressor of the spo1 null. CWP1 encodes a cell wall protein with a glycolipid moiety. We propose that, when modified by other lipases, this moiety may substitute for the product(s) of Spo1p lipase activity in meiosis. Based on the similarity of Spo1p to phospholipase B enzymes, its unique role in SPB duplication, and pleiotropic effects on MII, late gene expression and spore formation, we propose that the Spo1 protein participates in a novel meiotic pathway that functions through the SPB to coordinate nuclear division with spore development.

Genetic control of plasmid DNA double-strand gap repair in yeast, Saccharomyces cerevisiae.

The repair of double-strand gaps (DSGs) in the plasmid DNA of radiosensitive mutants of Saccharomyces cerevisiae has been analyzed. The proportion of repair events that resulted in complete plasmid DNA DSG recovery was close to 100% in Rad+ cells. Mutation rad55 does not influence the efficiency and preciseness of DSG repair. The mutant rad57, which is capable of recombinational DNA DSB repair, resulted in no DSG recovery. Mutation rad53 substantially inhibits the efficiency of DSG repair but does not influence the precision of repair. Plasmid DNA DSG repair is completely blocked by mutations rad50 and rad54.