The basidiomycete Coprinopsis cinerea is well-suited to studies of meiosis because meiosis progresses synchronously in 10 million cells within each mushroom cap. Approximately 20% of C. cinerea genes exhibit changing expression during meiosis, but meiosis and mushroom development happen concurrently and therefore differentially expressed genes might not be directly involved in meiotic processes...

The switch from mitosis to meiosis is controlled by the Pat1(Ran1) kinase-Mei2p system in Schizosaccharomyces pombe. Mei2p promotes both premeiotic DNA synthesis and meiosis I, and its RNA binding ability is essential for these two processes. Mei2p forms a dot structure in the nucleus prior to meiosis I, aided by a specific RNA species named "meiRNA". Pat1 kinase phosphorylates Mei2p on two pos...

The yeast C-type cyclin Ume3p/Srb11p and its cyclin-dependent kinase partner Ume5p/Srb10p repress the transcription of several genes required for meiotic recombination or meiosis I nuclear division. To relieve this repression, Srbllp is destroyed early in meiosis, prior to the first meiotic division. This report identifies two roles for Srb11p in regulating meiotic development. First, SRB11 is ...

With a quantitative approach it was possible to characterize the meiosis inducing activities of the ovary and the extra ovarian structures (rete ovarii). While the ovarian inducing capacity rises with age and remains high on days 14 and 15 post partum at the end of the prophase of the first meiotic division, the rete ovarii shows meiosis inducing activity up to day 5 post partum and an inhibito...

The origin of meiosis and its adaptive function in eukaryotes, and the related problem of the origin and adaptive function of sex in eukaryotes, are fundamental issues in biology. Among eukaryotes, meiosis and sexual reproduction are widespread, occurring in single-celled eukaryotes (including protozoans such as paramecium), and fungi (e.g. yeast) and in most multicellular organisms including a...

Meiosis, the process by which sexually reproducing organisms generate gametes (sex cells), is an essential precondition for the normal formation of the embryo. As sexually-reproducing, diploid, multicellular eukaryotes, humans [5] rely on meiosis [6] to serve a number of important functions, including the promotion of genetic diversity and the creation of proper conditions for reproductive succ...

In meiosis, a single round of DNA replication is followed by two consecutive rounds of chromosome segregation, called meiosis I and II. Disjunction of maternal from paternal centromeres during meiosis I depends on the attachment of sister kinetochores to microtubules emanating from the same pole. In budding yeast, monopolar attachment requires recruitment to kinetochores of the monopolin comple...

Smk1 is a meiosis-specific MAPK homolog in Saccharomyces cerevisiae that regulates the postmeiotic program of spore formation. Similar to other MAPKs, it is activated via phosphorylation of the T-X-Y motif in its regulatory loop, but the signals controlling Smk1 activation have not been defined. Here we show that Ama1, a meiosis-specific activator of the anaphase-promoting complex/cyclosome (AP...

The mechanisms regulating germ line sex determination and meiosis initiation are poorly understood. Here, we provide evidence for the involvement of homeobox Msx transcription factors in foetal meiosis initiation in mammalian germ cells. Upon meiosis initiation, Msx1 and Msx2 genes are strongly expressed in the foetal ovary, possibly stimulated by soluble factors found there: bone morphogenetic...

REC8 is a key component of the meiotic cohesin complex. During meiosis, cohesin is required for the establishment and maintenance of sister-chromatid cohesion, for the formation of the synaptonemal complex, and for recombination between homologous chromosomes. We show that REC8 has an essential role in mammalian meiosis, in that Rec8 null mice of both sexes have germ cell failure and are steril...