Summary of Features

Additional Non-Mammalian Model Organisms
February 1999 (Revised 2/17/99)


D. discoideum

T. thermophila

S. pombe

N. crassa



haploid chromosome #







200 Mb

~14 Mb

42.9 Mb

fraction sequenced


~0.1% (dispersed)

~70%(expected completion by end of 1999)

1%; funds awarded to sequence ~30%


10,000 (estimated)

~30,000 (from hybridization)

~5,000 (estimated)

12.000 (estimated)

cDNA/EST sequence




cellular organization

simple multicellular



multicellular (coenocytic)



germline (transcriptionally inactive) nucleus=2C; somatic (transcrip-tionally active) nucleus ~45C


haploid; a brief diploid phase occurs between caryogamy and meiosis

generation time

4 hours (cell ->cell)

zygote-> zygote=1-14 days; cell-> cell, binary fission, 1.5 hr. minimum

~10 hrs. from haploid ->diploid->haploid

sexual generation time is ~14 days; cell division time in vegetative growth is ~140’


3 days (spore->spore)


~2hrs to 3hrs doubling time



simple, inexpensive

simple, in complex or defined media


simple, inexpensive




yes; germline or somatic only;



gene inactivation

homologous recombination

gene knockout and antisense

by homologous recombination

Repeat-Induced Point (RIP) mutations; reciprocal homologous integration



many morphologicals

homozygous recessive and dominant; large variety


~1,200 that give rise to recognizable phenotypes


Cell Culture




indefinite storage of spores in fridge and cells in freezer












intact organisms


indefinite; freezing; slow growing maintenance cultures


indefinite at +4C if stored as conidia or mycelia; 10+years at +4 if stored as ascospores

  D. discoideum T. thermophila S. pombe N. crassa

Special Strengths

large scale screens;
excellent cytology

Mendelian genetic transmission; homologous meiotic and somatic recombination; excellent cytology; small introns; small amount of repetitive DNA; natural host for human pathogens; functionally distinct cilia; microtuble/dynein motility; microtubule heterogeneity; regulated secretion; phagocytosis; cytokine-dependent growth; regulated sexual maturation; related ciliate parasites

unicellular; defined colonies; haploid or diploid/ cheap, fast, amenable to "classical" and "molecular" genetics

best understood filamentous fungus; densest genetic map, most identified genes, most cloned genes, organized community; easy to grow; large collection of mutants; closely related to important plant pathogens and industrially important production organisms; molecular and regulatory characteristics typical of higher eucaryotes.



no specialized organs

unique genetic code (TAA/G=GLN);
relatively small research community

cytology difficult, but possible; limited development

no autonomously replicating vectors; multinucleate conidia; heterocaryotic transformants; no stable diploids



NICHD is providing funds to sequence the complete genome. This is a three year grant and the support for the current year is ~$1.2M.

genetic maps of DNA polymorphisms; cDNA, cosmid and YAC libraries;

much information on genetics and cell cycle; ~70% of genome sequenced; several culture collections

several culture collections, cDNA, and genomic libraries available via Fungal Genetics Stock Center;

two compendia describing all characterized chromosomal aberration stocks and all mutants with observable phenotypes now in print and being put on line; two fully searchable EST databases on the WEB; genome being sequenced; biannual Newsletter focusing on new stocks and techniques; all stocks available




Genetic Map Webpage;;

The Perkins et. al. compendia cross-referenced to genetic and molecular information are being put on line, fully searchable genetic stock and molecular biology technique and vector information is at

(, fullysearchable EST databases exist at

( and

( and the WEB page for the Neurospora genome sequencing effort is (


D. discoideum

T. thermophila

S. pombe

N. crassa



# of labs


~50 (mainly US, some in Europe and Japan)

>200 world-wide

~70 in US;~ 80 in rest of the world

# of investigators

492 on Dicty WWW server list


>1,000 (estimate)

250 in US; 250 in rest of the world


# of investigators

492 on Dicty WWW server list


>1,000 (estimate)

250 in US; 250 in rest of the world


Kuspa, A. and Loomis, W.F. Ordered yeast artificial chromosome clones representing the D. discoideum genome. PNAS USA 93:5562-5566.1996.

Maeda, Y., Inouye, K. and Takeuchi, I. [eds.] Dictyostelium.

A model system for cell and developmental biology. Universal Academic Press: Tokyo, Japan, 1997.

Parent, C.A., and P.N. Devreotes. Molecular genetics of signal transduction in Dictyostelium. Annu. Rev. Biochem. 65:411-440.1966.

Asai, D.J and J.D. Forney, eds. Methods in Cell Biology: Tetrahymena thermophila. Academic Press, San Diego, CA In press (1999).

Coyne, R.S., D.L. Chalker, and M.C. Yao. 1996. Genome downsizing

during ciliate development: nuclear division of labor through chromosome restructuring. Annu. Rev. Genet. 30: 557-578.

Gall, J.G. (1986). The molecular biology of ciliated protozoa (Orlando: Academic Press, Inc.).

Frankel, J. 1989. Pattern Formation: Ciliate Studies and Models. Oxford University Press, New York, NY.

Orias,E (1998): Mapping the germ-line and somatic genomes of a ciliated protozoan, Tetrahymena thermophila. Genome. Res. 8, 91-99.

Wheatley, D.N., L. Rasmussen, and A. Tiedtke. 1994. Tetrahymena: a model for growth, cell cycle and nutritional studies, with biotechnological potential. Bioessays. 16: 367-372.

Hoheisel et al., High resolution cosmid and P1 maps spanning the 14 Mb genome of the fission yeast S. pombe, Cell 73: 109-120 (1993).


Mizukami et al., A 13 kb resolution cosmid map of the 14 Mb fission yeast genome by nonrandom sequence-tagged site mapping, Cell 73: 121-132 (1993).


Nasim et al. (eds.), Molecular Biology of the Fission Yeast, Academic Press, 1989.


Broach et al. (eds.), Molecular and Cellular Biology of the Yeast

Saccharomyces cerevisiae, Cold Spring Harbor Laboratory Press, 1991.


Alfa et al. Experiments with Fission Yeast: A Laboratory Course Manual, Cold Spring Harbor Laboratory Press, 1993

Aramayo, R. and Metzenberg, R.L. (1996) Meiotic transvection in fungi. Cell 86, 103-113.

Nelson, M.A., et. al..(1997) Expressed sequences from conidial,mycelial, and sexual stages of Neurospora. Fung. Genet. Biol. 21, 348 - 363.

Perkins, D.D., et. al., 1982) Chromosomal loci of Neurospora crassa. Microbiol. Rev. 46, 426-570.

Selker, E.U. (1990) Premeiotic instability of repeated sequences in Neurospora crassa. Annu. Rev. Genet. 24, 579 - 613.

Perkins, D.D. Chromosome rearrangements in Neurospora. Adv. Genetics: 36. 239-399.

Information Provided By:

W. Loomis

M. Gorovsky

G. Smith; P. Nurse; B. Barrell; J. Sgouros

R. Metzenberg; J. Dunlap; M. Nelson


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