Ultrastructural studies of microconidium formation

Lowry, Robert J.; Durkee, Thomas; Sussman, Alfred S.

doi:10.4148/1941-4765.1976

Cited by 8 publications

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“…In the life cycle of N. crassa, both asexual and sexual sporulation require differentiation of a vegetative mycelium, and both are induced by nutrient deprivation (26,35,45). Upon carbon starvation, the vegetative mycelium undergoes a process whereby specialized aerial hyphae form, grow away from the substrate, and produce aerial constriction chains by repeated apical budding.…”

Section: Discussionmentioning

confidence: 99%

Molecular and Functional Analyses of poi-2 , a Novel Gene Highly Expressed in Sexual and Perithecial Tissues of Neurospora crassa

Kim

Nelson

2005

Eukaryot Cell

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The poi-2 gene is highly and specifically expressed in starved and sexual tissues of the filamentous fungus Neurospora crassa. It encodes a 27-kDa protein, as shown by in vitro transcription and translation. The POI2 protein contains a hydrophobic signal sequence at the amino terminus followed by novel 16 tandem repeats of 13 to 14 amino acid residues; all repeats are separated by Kex2 processing sites. Repeat-induced point mutation (RIP)-mediated gene disruption was used to generate poi-2 mutants, and the mutated sequences showed either one of two distinct patterns: typical RIPs (GC-to-AT transitions) or insertion-deletion (indel) mutations. Although the poi-2 strains contained numerous mutations, all retained intact open reading frames (ORFs) of various lengths. They showed greatly reduced vegetative growth and protoperithecial formation and low viability of their sexual progeny. All poi-2 mutants had similar defects in male fertility and the mating response, but the nature of female fertility defects varied and corresponded to the length of the residual poi-2 ORF. Mutants with ORFs of approximately normal length occasionally completed sexual development and produced viable ascospores, while a mutant with a severely truncated ORF was female sterile due to its inability to form protoperithecia. Thus, poi-2 is essential for differentiation of female reproductive structures and perithecial development as well as for normal vegetative growth. The POI2 protein is involved in the mating response, probably as a component in the pathway rather than as a pheromone.Neurospora crassa is a heterothallic fungus with two mating types (mat a and mat A); the decision whether to undergo asexual or sexual development is made based on environmental signals. Under conditions of nitrogen starvation, light, and low temperature (35, 38), vegetative hyphae undergo differentiation in preparation for the sexual reproductive pathway, aggregating to form a spherical prefruiting body, the protoperithecium. When fertilized with a nucleus of the opposite mating type, the protoperithecium develops into a perithecium (fruiting body), within which asci are formed from successively developing hook-shaped hyphae (croziers). Inside the developing asci, the diploid zygote nucleus undergoes meiosis followed by a postmeiotic mitosis. The resulting eight nuclei are sequestered into eight linearly ordered homokaryotic, haploid ascospores, and the ascospores are ejected after further maturation.N. crassa has a long history in classical and biochemical genetics, but relatively little is known about sexual development at the molecular level. Nelson and Metzenberg isolated 14 genes that are preferentially expressed during sexual development and named them sdv genes, for sexual development (31). A mutant with a disrupted sdv-10 gene, which was renamed ascus development 1 (asd-1), was isolated using the repeat-induced point mutation (RIP)-based reverse genetic technique (43, 44). Another mutant (asd-2) was created by random integration of transforming DNA i...

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Section: Discussionmentioning

confidence: 99%

Molecular and Functional Analyses of poi-2 , a Novel Gene Highly Expressed in Sexual and Perithecial Tissues of Neurospora crassa

Kim

Nelson

2005

Eukaryot Cell

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“…Extensive (Lowry et al, 1967) Sparse to moderate (Lowry et al, 1967) Mitochondria Few, 1 µm long (Lowry et al, 1967) Many, Ͼ2 µm (Lowry et al, 1967) Hydrophobicity Hydrophilic Hydrophobic Germination rate Slow and asynchronous, 6-48 h (Kalpana et al, 1998) Rapid and fairly synchronous, 2-4 h Plating efficiency Low, ϳ20-35% (see Table 3) High, ϳ65-95% (Haard, 1967;Wellman, 1960;Fahey et al, 1978;and R. Maheshwari, unpublished (Pandit and Maheshwari, 1996) High sugar and nitrogen (Pandit and Maheshwari, 1996) …”

Section: Endoplasmic Reticulummentioning

confidence: 99%

“…Microconidia Macroconidia Size 2.5 ϫ 3.5 µm (Dodge, 1930); 2.43 ϫ 3.98 µm (Barratt and Garnjobst, 1949) 5-9 µm (Lowry et al, 1967) Shape Ovoid to pear-shaped (Lowry et al, 1967) Oblong to spherical (Lowry et al, 1967) …”

Section: Parametermentioning

confidence: 99%

Microconidia ofNeurospora crassa

Maheshwari

1999

Fungal Genetics and Biology

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“…Unlike formation of macroconidia, the smaller, uninucleate microconidia are produced within the hyphae and rupture through the hyphal cell wall as independent morphological entities ( Fig. lc, d) (Lowry et al 1967;Rossier et al 1973). The sexual cycle is activated specifically by nitrogen starvation ( Ricci et al 1991).…”

Section: Presence Of Coni O Protein In Other Developmental Structuresmentioning

confidence: 99%

Expression of con genes along the three sporulation pathways of Neurospora crassa.

Springer

Yanofsky²

1992

Genes Dev.

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The filamentous fungus Neurospora crassa produces three types of spores by using different developmental pathways: macroconidiation, microconidiation, and sexual spore (ascospore) formation. Several genes of unknown function have been cloned by virtue of their expression during macroconidiation but not during mycelial growth (con genes). It had been postulated that expression of the con genes was specific to macroconidiation. To test this assumption, protein extracts from macroconidia, microconidia, ascospores, and protoperithecia (sexual structures) were analyzed for the product of one of the con genes, con-lO, by immunoblotting using a CON10-specific antiserum. CON10 was detected in all of these extracts. An immunologically related protein was detected in an extract from ascospores of a nonconidiating Neurospora species, N. africana. Total RNA isolated from the three types of N. crassa spores was analyzed for con gene mRNA by Northern blotting using five different con genes as probes. Transcripts for four of the genes were detected in all three spore types; mRNA for the fifth gene was detected in macroconidia and microconidia but not in ascospores. Analysis of aconidial and female sterile mutants showed that expression of the con genes along any one developmental pathway occurs when expression along another pathway is genetically blocked.

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Ultrastructural studies of microconidium formation

Abstract: Ultrastructural studies of microconidium formation This spores is available in Fungal Genetics Reports:

Cited by 8 publications

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Molecular and Functional Analyses of poi-2 , a Novel Gene Highly Expressed in Sexual and Perithecial Tissues of Neurospora crassa

Molecular and Functional Analyses of poi-2 , a Novel Gene Highly Expressed in Sexual and Perithecial Tissues of Neurospora crassa

Microconidia ofNeurospora crassa

Expression of con genes along the three sporulation pathways of Neurospora crassa.

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