Pathway analysis of radiation-sensitive meiotic mutants ofCoprinus cinereus

Abstract

We have isolated 37 radiation-sensitive mutants of the basidiomycete Coprinus cinereus. Each mutation is recessive, and the collection defines at least ten complementation groups for survival of gamma irradiation. Four complementation groups define the genes rad3, rad9, rad11 and rad12, which are required both for survival of gamma irradiation and for meiosis. Mutants in each of these four groups fail to complete meiosis and produce mushrooms with greatly reduced numbers of viable spores. Propidium iodide staining of meiotic nuclei showed a characteristic terminal appearance for each mutant: few cells of any of the meiotic mutants progress beyond prophase I, and both condensation and fragmentation or dispersal of meiotic chromatin are frequently observed. Scanning electron micrographs showed that the meiotic mutants make varying numbers (0-6) of basidiospore initials and that few of these initials develop into mature spores. When initials are present they are always symmetrically arrayed on the basidium, regardless of initial number. In quantitative measurements of gamma ray sensitivity, double mutants of every tested combination of rad3, rad9, rad11 and rad12 consistently showed the same gamma ray sensitivity as the more sensitive single mutant parent of the cross. Therefore, these four genes are in the same pathway for the repair of gamma radiation damage, and this pathway also represents one or more functions essential for meiosis.

Life History and Developmental Processes in the BasidiomyceteCoprinus cinereus

“…Other studies report defects in premeiotic DNA replication and meiotic prophase I, but the majority of defects appear to be localized at the stage of meta-anaphase I (216,389,396,397,405,435,466,498,502,538,539,542). From ␥-radiation-sensitive mutants exhibiting defects in chromosome condensation and synapsis in meiosis, an epistasis group of rad3-9-11-12 has been defined (405,498,538,542). The first genes involved in meiosis and DNA repair (rad9, rad11/mre11, and spo11) have been isolated by mutant complementation and by a two-step, semirandom PCR recovering DNA inserts of a REMI mutant ( (101,130,539,542).…”

“…Two other genes act in sterigma formation following meiosis, 13 genes are involved in prespore formation, and 4 genes contribute to nuclear migration into the spores (214). Other studies report defects in premeiotic DNA replication and meiotic prophase I, but the majority of defects appear to be localized at the stage of meta-anaphase I (216,389,396,397,405,435,466,498,502,538,539,542). From ␥-radiation-sensitive mutants exhibiting defects in chromosome condensation and synapsis in meiosis, an epistasis group of rad3-9-11-12 has been defined (405,498,538,542).…”

Functional links between Drosophila Nipped-B and cohesin in somatic and meiotic cells

“…Nipped-B encodes a member of a highly conserved protein family, which includes Scc2 and Mis4 of S. cerevisiae and S. pombe, discovered in screens for factors that control sister chromatid cohesion (Furuya et al 1998;Michaelis et al 1997), C. cinereus Rad9 identified in a screen for factors required for deoxyribonucleic acid (DNA) repair and meiosis (Valentine et al 1995), and human Nipped-B-Like (NIPBL/delangin), mutated in Cornelia de Lange syndrome (CdLS; Krantz et al 2004;Tonkin et al 2004). Nipped-B family proteins contain seven HEAT repeats implicated in protein-protein interactions (Neuwald and Hirano 2000), and NIPBL missense mutations in all seven cause CdLS Miyake et al 2005;Deardorff and Krantz, personal communication).…”

Coprinus cinereus rad50Mutants Reveal an Essential Structural Role for Rad50 in Axial Element and Synaptonemal Complex Formation, Homolog Pairing and Meiotic Recombination

“…The members of the Mre11 complex have been grouped by epistasis analysis (Game et al 1980;Malone and Esposito 1981;Ivanov et al 1992;Ajimura et al 1993;Valentine et al 1995) and have been shown to directly interact ( Johzuka and Ogawa 1995;Petrini et al 1995;Dolganov et al 1996;Trujillo et al 1998;Varon et al 1998). Mammalian deletion mutants of the Mre11 complex exhibit embryonic lethality (Xiao and Weaver 1997;Luo et al 1999;Yamaguchi-Iwai et al 1999;Zhu et al 2001).…”

“…C. cinereus has naturally synchronous meiosis (Raju and Lu 1970), well-developed cytogenetics (Pukkila et al 1984;Pukkila and Lu 1985;Seitz et al 1996;Li et al 1999), and an annotated genomic sequence (Stajich et al 2006). In screens for mutants defective in both the survival of gamma radiation and meiosis (Zolan et al 1988;Valentine et al 1995), we identified four complementation groups, termed rad3, rad9, rad11, and rad12. These four genes are all part of the same gamma radiation survival pathway (Valentine et al 1995;Cummings et al 2002).…”